GENERAL SPECIFICATIONS

A Technical Note On the RESTORATION OF

STONE and MASONRY

In Historic Buildings

Historic Preservation Series

National Historical Institute

2005

2005 National Historical Institute All Rights Reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording or any other information storage and retrieval system, without prior permission in writing from the publisher.

ISBN

Advisory:

Prior to the use or adoption of these technical note or part thereof in developing conservation strategies for heritage structures, conservation assessment and study of the existing structure should be undertaken. In the same manner, testing should be done prior to any application of conservation treatments or procedures, which should also be supervised by trained specialists. The NHI is not liable for any effect or damage on structures that may result from unscrupulous use or application of these general notes. The publisher welcomes suggestions or comments from the public.

Contents

ForewordIntroduction/1Definitions, Objective and Scope/1General Conservation Principles/1

Stone Building and Common Philippine Stone and Masonry Materials/2

Causes of Stone Deterioration/2Morphology of Stone Deterioration/2

Restoration of Stone and Masonry in Historic Buildings/A. Documentation of Stone and Masonry in Historic Buildings/

State of Conservation Record/B. Actual Methods of Restoration/

Mortars

Lime in Mortars/

Cement in Mortars/

On the Use of Traditional Mortars/

Mortar Mixtures/

Admixtures/

Coloring/

Cleaning of Stone and Masonry Walls/

Soiling and Surface Deposits/

Salts/

Mechanical Cleaning/

Cleaning by Washing/

Chemical Cleaning/

Special Cleaning Methods/

Stone Consolidation/

Lime Method/

Lime Water Preparation/

Grouting injection in Masonry/

Replacement of Stone and Masonry Units/

Replacement of Coral Blocks/

Repointing of Masonry Joints/

C. Preventive Conservation for Stone and Masonry Buildings/

Surface Treatments/

Storm Water Drainage and Disposal/

Protection from Bird/Bat Droppings

Repair, Maintenance and Surface Protection/

D. Structural Restoration of Stone and Masonry Walls/

Glossary/

References and Suggested Reading/

Annex 1 International Charter for the Conservation and Restoration of

Monuments and Sites/

Annex 2 ICOMOS Proceedings of the 6th General Assembly and of the International

Symposium No future without a past/

Annex 3 NHI Graphical Lexicon for Mapping Common Stone and Masonry Morphologies/List of Illustrations

Morphology of Stone Decay and Alteration

Fig. 1Presence of Vegetation. Grass and higher plants on stone structure/

Fig. 2Algae on stone wall/

Fig. 3Woody plants and roots on and around stone walls/

Fig. 4Mosses on stone walls/

Fig. 5Lichens on brick surface/

Fig. 6Efflorescence. Soluble salts on brick surface/

Fig. 7Black deposits on faade cornice/

Fig. 8Black deposits on balcony wall, ledge and upper cornice of niche wall/

Fig. 9Loss. Note the loss of masonry units/

Fig. 10Erosion. Note the erosion of a stepped church buttress/

Fig. 11Example of erosion of stone masonry units/

Fig. 12Pitting. Deterioration of a stone masonry unit characterized by pits/

Fig. 13Alveolar Decay. Example of alveolar decay of a brick block/

Fig. 14Pulverization. Example of a common form of deterioration/

Fig. 15aFissuring or Cracking. Example of a crack running horizontally and diagonally/

Fig. 15bExample of a vertical crack/

Graphic Documentation

Fig. 16Manual Tracing (Scale 1:1)/

Fig. 17West Wall Geomorphology of Alteration and Decay, Paoay Church/

Anatomy of a Masonry Wall

Fig. 18Parts of a masonry wall/

Fig. 19Photo of a deteriorated masonry wall/

Different Levels of Cleaning

Fig. 20Different levels of removing dirt/

Dry and Wet Cleaning Procedures

Fig. 21aDry Cleaning Procedure/

Fig. 21bWet Cleaning Procedure/

Chemical Application Procedures for Woody Plants

Fig. 22Chemical application for woody plants/

Mechanical Cleaning and Chemical Treatment

Fig. 23Mechanical cleaning. Use of nylon brush/

Fig. 24Chemical treatment. After woody plants are cut, herbicides are applied/

Fig. 25Application of herbicides at stone crevices/

Poultice Method of Cleaning

Fig. 26Use of sepiolite or clay as poultice/

Fig. 27Application of Mora poultice on stone surface/

Fig. 28Stone surface after poultice removal/

Fig. 29The stone surface is cleaned of the remaining poultice/Documentation Before and After Removal of Biological Growth

Fig. 30Removal of vegetal growth at church bell tower. Bell tower before cleaning/

Fig. 31Bell tower after cleaned of vegetation/

Fig. 32Stone detail before and after cleaning. With vegetation/

Fig. 33After removal of vegetation/

Documentation Before and After Poultice Method of Cleaning

Fig. 34Poultice Method on Stone Reliefs/

Fig. 35Application of poultices on reliefs/

Fig. 36After poultice treatment/

Repointing of Masonry Structures

Fig. 37Repointing/

Fig. 38Appropriate repointing procedures/

Preventive Conservation MeasuresFig. 39Proper storm drainage system/

Fig. 40Rainwater downspouts directed at the base of stone and masonry structures/

Fig. 41Protective screens/

Fig. 42Spikes may be introduced on ledges of stone structures/

Fig. 43Diagnostic measures for moisture content/

Fig. 44Burning of dead leaves and twigs/

Fig. 45Growth of plants/

Foreword

The Philippine architectural landscape is featured with varied historic sites and structures that are made up of stone and masonry. Currently in varying states of preservation, these structures need to be restored and maintained for their distinct historical and architectural values.

Frequently, the architect and craftsman are faced with the problem of stone and masonry deterioration, diagnosing the possible causes and formulating solutions for treatment and prevention. Where historic buildings are concerned, the problem gains a more complex nature. Heritage site recording takes on significance while understanding and recognition of stone decay and traditional stone building techniques become necessary.

A Technical Note on the Restoration of Stone and Masonry in Historic Buildings attempts to present in simple and straightforward manner the technical process of restoring stone and masonry from general conservation principles and basic recognition of stone decay to the more intricate processes of cleaning and structural intervention. Hence, this manual is a must have for professionals, tradesmen and other technical practitioners of conservation work, particularly on stone and masonry restoration and repair.

To the reader, the National Historical Institute presents to you its humble contribution to the field of architectural conservation.

AMBETH R. OCAMPO

Chairman

National Historical InstituteIntroduction

A Technical Note on the Restoration of Stone and Masonry Structures in Historic Buildings is published by the National Historical Institute (NHI) as a first in a projected series of technical conservation manuals. Based on internationally accepted conservation standards and methods and the National Historical Institutes experience in the field of architectural conservation, it is designed to give a general overview and understanding of the process of restoring stone and masonry structures.

This work includes discussions on cases of deterioration and its manifestations, remedial actions, preventive conservation measures, and illustrations in the form of drawings and photographs for better understanding of the involved technical processes. Prior to the implementation of stone conservation procedures, the historic structure should be analyzed for its own specific needs and requirements. In such cases, inspections, documentation, studies and diagnostic tests are undertaken. The restoration process requires careful analysis, study, and, ideally, the involvement of different disciplines in order to come up with a wholistic, scientific and creative conservation program that will also include the preservation of the historic structures authenticity.Definitions, Objective and Scope Restoration is defined as the means of intervention with the aim of maintaining intact the material heritage, in this case a structure, and transmitting it to the future, in all its integrity (Venice Charter, 1964).The main objective of restoration is the maximum conservation of the original existing structures and features, and the least possible intervention, alteration, addition, replacement or deduction of existing parts, components or features.

The aim of restoration is not to return the object or artifact to its primitive splendor. Rather, it is to conserve the originality of the object as it appears after so many years have passed since its completion. This refers to the objects existing appearance. Factors that detract from the correct interpretation of the structure, such as deterioration, must be removed.

In this technical note, stone is defined as rock selected or processed by shaping, cutting or sizing for building or other use. Masonry will refer to man-made works or structures composed of stone or brick, including the mortars, joints, plasters and renders therein.

Alteration will refer to physical changes brought about by naturally occurring phenomena and not necessarily by the diminished natural, mechanical and structural properties and capabilities of the masonry material. On the other hand, deterioration indicates a negative effect on the natural, mechanical and structural properties of the masonry material or assemblage.

Conservation measures for stone and masonry should prevent and slow down primarily the process of decay or deterioration. This includes recognition of the manifestations of deterioration and their possible causes. Remedial actions may then be undertaken involving the following:

1. Treatments on the material surface, base of the structure or inside the stone or masonry structure;2. Replacement of deteriorated masonry units; 3. Structural interventions;

4. Improvements or corrections in building design or specifications. Interventions and improvements should be supported by preventive conservation measures. These may involve repair and maintenance works including regular diagnostic tests on the structure, setting up of security measures against possible human or animal vandalism, and a campaign to generate awareness and recognition of the possible causes of decay or damage to stone structures.General Conservation Principles

When planning the restoration of masonry in historic buildings, the following principles should be considered:

1.Any intervention or process to be introduced should be reversible;

2.The least intervention is the best restoration;3.The structure must be safe and sound for whatever purpose or function the old structure shall be used;

4.The best restoration technique is that which will restore the original structural logic and fabric; and

5. When introducing new materials or processes into the old, the new must match the strength of, or be slightly weaker than the old.

Any new addition or change must always refer to the existing structure. Any intervention planned must be supported with tests in the laboratory or in situ. Documentation is necessary in all phases of works to be undertaken.Stone Building and Common Philippine Stone and Masonry Materials

Stone building in the Philippines was introduced by the Jesuit Fr. Antonio Sedeo in the 1580s. In time, many became involved in the stone building, especially the Chinese, so that in due time many became skilled stonecutters, lime burners and masons. Bishop Domingo de Salazar brought with him Chinese laborers to the quarries of Guadalupe where he sourced the stones to build his house in Manila. Eventually, the bishops house became the first stone structure in Manila.

Throughout the country are stone and masonry structures with most of them dating back from the Spanish colonial period. They include, among others, churches, convents, houses, fortifications, schools, tribunals and bridges. They display not only the traditional art and techniques of stone and masonry building but also unique architectural features and cultural details.

Stones commonly found or used in historic buildings include volcanic tuff, or what is locally known as adobe, and limestone. Limestone has its variants including coral and coralline limestone. River stones were also used together with other stone materials for masonry corework before walls were faced with cut stone veneer. For pavements, Chinese granite or piedra china was used especially during Spanish colonial times.

Brick was also a common construction material used homogeneously or as a composite material. Brick was fired in specially designed kilns or hornos. Today, some of these hornos or their remnants can still be found in the Cagayan valley.

Spanish stone-building tradition introduced the use of cut stones for masonry which used lime primarily as binder to the masonry materials. Sillera or cal y canto (lime and cut-stone) was ashlar or cut-stone masonry work. Mampostera would refer to rubble masonry work.

Stones were referred to sometimes through the quarries from where they were sourced, as in piedras de Meycauayan, piedras de Guadalupe, piedras de Visayas (coralline stones) and sillares de San Juan del Monte. Stonemasons or stone-workers were referred to as pedreros.

Traditional masonry practices included using wood sap, egg whites, blood, honey and even gum arabic as binding medium in addition to slaked lime. This was believed to produce a more stable mortar. Mortar was used not only as bedding but also as protective render or plaster to walls. Plaster was referred to during Spanish times as paletada. Lime mixed with water was known as argamasa (Jose 1994).

Causes of Stone Deterioration

Deterioration in stone and masonry work can be manifested physically in the state of the masonry assemblage and its constituent parts especially in the stone and or brick parts, mortars, and renders. The causes of stone and masonry deterioration may be categorized generally as due to the following:

1. Mechanical weathering This type of weathering is caused by factors such as vibrations, ground movements, materials expansion, temperature changes and extremes, and frost and salt bursting.2. Chemical weathering - This includes reactions to processes like oxidation, chemical dissolution, photochemical processes and precipitation of dust, acids and gases. Efflorescence or the presence of salts and black crust formations on stones is a form of chemical weathering.

3. Biogenic weathering - This weathering includes vegetal and microorganism metabolism and growth, erosion, and root cracking. Animal and human abuse, misuse and neglect are also factors for this weathering type.

Factors causing deterioration of stone materials may also be classified into external and internal agents. External agents include outside movements, vibrations, calamities like fires, earthquakes, tornadoes and floods, dust, precipitation of acids and gases, temperature and humidity changes, and actions of organisms, including animals and men. Internal factors or agents of deterioration include humidity in the stone or masonry material, salt formations, organisms, use of incompatible materials, and acids and alkaline materials (ISSC 2001).

Morphology of Stone Deterioration

It is important for a conservator or restorer to be able to identify the different physical manifestations of stone and/or masonry deterioration in order to diagnose possible causes and plan conservation strategies that may include prevention, protection and control.

The following are just some of the common examples of macroscopic deterioration on stone objects.

1. Surface deposits

Surface deposits refer to the accumulation of foreign material of a nature different from the stone material such as dust, dirt, and animal droppings.

Dark deposits include soiling, compact black deposits and dendritic black crusts. Soiling refers to brownish or grayish incoherent deposits that do not completely hide the stone surface and where the tools marks are still visible.

Compact black deposits completely hide the stone surface with a smooth black layer.

Dendritic black crusts refer to dark deposits completely hiding the stone surface with considerable thickness and rough surface.

Calcareous concretions are compact deposits of limited size and isometric form. They may come in stalactite or stalagmite forms.Efflorescence is a crystalline formation of soluble salts on the surface of a stone. Salt migration and evaporation of the material primarily cause it.

Animal droppings include waste droppings from animals such as birds and bats.Presence of vegetation or biological growth refers to growth of lichens, moss, fungi, algae, liverworts and higher plants on or within the stone structure.

Staining refers to presence of stains or discolorations on the surface of the stone which are due to, among others, iron oxide and copper salts.

2. Stone surface condition or material loss

Alveolar decay refers to deterioration, which appears in highly porous materials in the form of cavities, often deep and interconnected, the walls of which are covered with powder from the stone material itself.

Pitting is the formation of numerous punctiform small holes or pits in the stone material.

Pulverization occurs when material is reduced in powder form, whether spontaneously or induced by certain causes.

Disaggregation indicates a lack of cohesion in the composition of the stone material resulting in a rough stone surface.Blistering occurs when there is a localized bursting of raised areas in the stone.

Erosion is characterized by the partial loss of the surface, especially by the loss of sharp contours or arrises in the stone.

Deformation refers to a change or variation in the profile of the stone material.

Detachment is the loss of continuity between the superficial layers of the stone material with respect to the substrate.3. Structural condition

Fissuring or crack is deterioration that appears with the formation of discontinuities in the material, with or without displacement of the two sides.

Fractures refer to breaking or splitting of stone or masonry with displacement of the two sides.Losses refer to loss of missing parts.

Open Joints include gaps or areas created by loss of binding material between masonry units.

Loose or disconnected parts refer to masonry units which are not firmly fastened to or attached to the rest of the masonry assemblage.For examples of stone deterioration, see Figs. 1-15.

Restoration of Stone and

Masonry in Historic BuildingsA. Documentation of Stone and Masonry in Historic Buildings

Restoration should include in its program the documentation of the historic structure. Documentation includes not only historical data, which may be obtained through library or archival research and interviews, but also a graphical record of the building. The graphical record will provide a clear appreciation of the existing physical condition of the historic structure. This may include appearance, measurements, materials, defects and damages, previous interventions, and other existing physical attributes. Actual condition photographs form part of preliminary records, while rectified photographs and measured drawings are part of detailed records. See Fig. 16.

Recording of stone and masonry buildings should include a map of the geomorphology and chronology of construction of the stone and masonry structure.Existing condition photographs and sketches of wall surfaces and other important details serve as BEFORE RESTORATION documents. Records of actual phases of restoration work refer to as DURING RESTORATION records. These will become good reference materials for future works on the structure. Documentation taken after completion refer to AFTER RESTORATION records.

Documentation provides a useful reference in monitoring the state of conservation of a historic structure through periods of time. It helps identify possible causes of deterioration by assisting in recognizing processes, cycles and patterns of change or transformation. It serves not only as an insurance against loss but also as a guide for future conservation plans and proposed intervention measures. State of Conservation RecordA state of conservation record is necessary prior to the onset of actual restoration or intervention. This includes graphic documentation of the following:

1. Block division

2. Constituent materials

3. Conservation conditions

4. Structural conditions

5. Previous interventions

The block division record shows the arrangement or coursing of the masonry units. The constituent materials record indicates the surface render or plaster and the stone materials which the specific wall or surface is made of. The record for conservation conditions indicates macroscopic forms of deterioration such as surface deposits, rust or cuprous stains, and biological growth. The structural conditions record indicates deterioration in the structural make-up of the wall or surface such as fissures and deformations. Previous interventions would refer to polychromy, artificial patina, paint applications, graffiti, new fillings, insertions, clamps, pins, previous surface treatments and material replacements.For conservation conditions and previous interventions, the NHI has adopted a graphical lexicon based on the Italian NORMAL Document No. 1/88 and the English Heritage lexicon with their graphical standards for mapping the geomorphology of historic buildings. See Fig. 17 and Annex 3.

At each sheet of state of conservation record, it is advised to insert a legend for the plotted physical characteristics, together with the date and name of the recorder or documentator. B. Actual Methods of Restoration

1.0 Mortars

Mortar is the plastic mixture or combination of binder and other components such as aggregates and admixtures with water. Mortars are used to bind together masonry units.Binders are natural or artificial materials that make possible the adhesion of aggregates. The main types of binders are clay, gypsum, lime, and Portland cement.Aggregates are materials added that may be natural or artificial. Natural aggregates include sand, crushed stones and pozzolana while artificial ones include ceramic or pottery sherds or crushed bricks. Admixtures are additives to the basic binder and aggregates ratio. They are used to improve the quality or properties of mortar such as setting or workability (Borrelli 1999).

Mortars can be used for external or internal renders or plasters, masonry bedding, joint pointing and even grouting. See Figs. 18 and 19. Lime in Mortars

Lime is a binding material used in preparation of mortar since ancient times. It is obtained from limestone, which is essentially calcium carbonate. Lime is also the main component present in its various physical and chemical forms such as quicklime, hydrated lime and hydraulic lime (Borrelli 1999).

Quicklime or calcium oxide is obtained by heating limestone in a kiln at 850-900 C. The process of adding water to quicklime is known as slaking. Lime putty is slaked quicklime that is stored in a pit and covered with excess water. The longer the lime is slaked, a softer, more plastic and more workable lime putty is produced.

When quicklime is chemically combined with the right amount of water, hydrated lime is produced. When a large amount of water is added to slaked quicklime or hydrated lime, limewash is produced. Limewash is applied as a coating resulting in a white finish.

In the setting of lime mortars, carbonation occurs. Carbonation is the process by which slaked lime or hydrated lime sets or hardens through the reaction with carbon dioxide form the air and the evaporation of water Borrelli (1999).

The saturated solution of hydrated lime reacts with carbon dioxide in the air, starting from the outer exposed layer and gradually into the inner layers, creating a film of calcium carbonate or lime. The evaporation of the mixing water results in shrinkage which allows carbon dioxide from the air to penetrate the layers and react again with the hydrated lime, thus, starting again the lime cycle. This results in the further and gradual hardening of the lime mortar. As long as there is evaporation of water, carbonation will occur and progress towards the inner layers (Borrelli 1999).

Limestone

Quicklime

Reaction with CO2

in the air

Water Slaked Lime

THE LIME CYCLE Source: Binders, Borrelli, 1999When hydrated lime is mixed with pozzolana and other similar volcanic materials, a faster setting occurs even in the absence of air or carbon dioxide. This is the basis for Roman concrete which is slaked lime mixed with pozzolana and tuff.

Hydraulic lime, which is another type of binder, is a dry product produced by burning limestone containing silica and alumina at a temperature above 900 C.

Another binder is Portland cement which is obtained by pulverizing a clinker obtained by firing clay and limestone at a temperature above 1400 C. It is made up essentially of calcium silicates and aluminates. Cement in Mortars

Portland cement has been considered inappropriate for conservation use because of its capacity to harbor soluble salts, high mechanical resistance and low porosity. Although lime mortars are considered ideal for conservation use, cements discreet and careful use may even assist in actual restoration works. Cement may be used in conservation mortars under certain conditions in combination with lime and the appropriate aggregates. With the use of cement, the mortars can attain strength at a suitable setting time in comparison to mortars using pure lime whose carbonation process will take considerable time before hardening of the lime mortar is attained to the maximum.

The use of lime in plasters and renders was superseded when Filipino masons and construction workers got used to working on modern building and civil works construction where value engineering and modern construction management demanded high performance cement formulas to shorten and speed up the time of construction.

This practice may be problematic for conservators who would want to introduce the least possible damage to stone or masonry work in historic buildings. A pure cement coat that will come in contact directly with the stone or masonry work has been historically proven damaging. Thus, it is necessary to use scrupulously and discreetly cement in historic preservation work.

On the Use of Traditional MortarsA popular misconception regarding mortars is that: Conservation mortars should be the same as the old mortar, in materials and composition. It implies that if the old mortars used lime, sand (filler), animal blood (binder), egg (binder), animal hair (strengthener), and then the repair mortar should use exactly the same materials.Old mortar is made up of old materials which had set over a period of time. If the old mortar composition is adopted for new conservation mortar, this composition will still be new material, which will only start setting upon application on the old surfaces or in the joints of the old masonry or stone structure.

Therefore, technically speaking, we are applying new material, with a traditional composition, on old material. Although they are of the same composition, the new repair mortar will differ in its mechanical properties from the old mortar whose own properties have changed or may have been weakened over the passage of time. One should consider also environmental effects and the inherent reactions of the old material to change over time.

While it may be an ideal and romantic solution to employ traditional technologies in conservation, these may not always be viable in the context of present day issues like diminishing and endangered natural resources, poverty, discontinuity or loss of traditional technology and financial constraints. One intention of using present day or compatible composite technologies, as against purely traditional techniques, is also to simplify the complex operation and cost of restoration, and to match the physical properties, and not necessarily the material composition of the old mortar. In the past, mortars did not use lime as the sole binding agent but also other materials that were thought to improve the workability and performance of the mortar. These included animal blood, egg white, gum arabic, and wood sap among others. The use of organic materials in old mortars was the result of applied and proven ancient resources and past technologies. As technologies developed and improved, so did the methods and logic of construction. Today, the use of corals in conservation may be subordinate only to the more pressing need to preserve the ecological balance. Therefore, finding modern substitute materials is prioritized over unlawful extraction of corals.

New materials are used, whether traditional, modern or a combination of both, that have compatible or the same physical qualities as the old, e.g. hardness, porosity, binding strength, tensile strength. This is also the same in the use of present day technologies in developing appropriate conservation solutions for stone conservation.

The demands of economy and todays construction or building standards and requirements should be considered in the decision on whether or not to use traditional organic materials for mortars. In the same way, new materials may be perceived as more economical and logical to use if tested to meet the qualities of the old mortar or old admixture. (Sickels 1982).

2.0 Mortar Mixtures

The following mortar mixes are presented based on the principle of creating a mortar grout mix with equal or lower strength than the stonework to be restored. Additives may be introduced in the form of marble dust and adobe chips/powder with the mortar.

Weak or low strength mortar mixes are more flexible and allow for better thermal and moisture movements. Stronger mixes are more frost and salt resistant. However, with very strong mortar mixes, moisture and salt may attack the masonry first and not the mortar (Fidler 2001). In this sense, mortars and plasters also function as sacrificial renders, where salts and frosts settle, and are removed and replaced in due time for the proper conservation of the underlying stone and masonry work.

Roman mortars used non-hydraulic (air) lime to which they added pozzolan for quicker setting, strength and water resistance in specific instances. Experiments with mortars using hydraulic lime and cement began since the medieval period in Europe. Use of commercially produced cement began in the 19th century (Fidler 2001).

For mortar mixtures, one may use a proportion of non-hydraulic lime putty:sand from the weakest ratio of 1:1 to the strongest ratio of 1:3. Mortars using these materials, though, need to be protected for several months until carbonation set takes place, especially in wet and cold environments. In hot and dry areas, mortars are protected from the sun and wind and kept damp for several days. This mortar mixture is ideally perceived as the weakest, most flexible, porous and permeable (Fidler 2001).

Another mortar mixture uses hydraulic lime and sand. This is considered stronger, quicker setting, less flexible but still relatively porous and permeable than the non-hydraulic lime putty: sand mixture. It may be used from the weakest hydraulic lime: sand ratio of 1:3 to the strongest of 1:1 (Fidler 2001).

The following mortar mix proportion uses hydraulic lime, cement and sand and is given from weak or very low to high strength (MCG 1982). This mortar mix proportion is stronger, quicker setting, less flexible, less porous and permeable and has higher salt content. The following ratios are not absolute and should also be tested to their applicability or appropriateness based on the desired mortar strength: a. For very low strength: (1:3 base of binder: filler ratio). This is good for plasters, renders or for low strength mortars.

1 part cement (Portland Type I, white Portland or Pozzolan) - binder

3 parts lime (hydraulic) - binder

12 parts sieved sand filler

Q: How is the ratio 1:3 established in this proportion?

A: If we add the two binding components, which is 1 and 3, we get 4 parts binder. Therefore, the binder:filler proportion is 4:12 or 1:3.

b. For moderate strength: (1:3 base) This is the better alternative and widely used mortar mix

1 part cement (Portland Type I, white Portland or Pozzolan)

2 parts lime (hydraulic)

9 parts sieved sand

c. For good strength: (1:3 base)

1 part cement (Portland Type I, white Portland or Pozzolan)

1 part lime (hydraulic)

6 parts sieved sand

d. For ideal strength for bricks: (1:2 base)1 part cement (Portland Type I, white Portland or Pozzolan)

1 part lime (hydraulic)

4 parts sieved sand

e. For special applications

1 part cement (Portland Type I, white Portland or Pozzolan)

1 part lime (hydraulic)

part brick or adobe powder (grog or shrinkage reducer)

4 parts sieved sand

The above mortar proportions should be considered as trial mixtures and should be tested in-situ on the specific structures where restoration is to be undertaken.

White Portland cement is weaker than Type I Portland cement, and the use of Pozzolan cement requires lesser water in the mix preparation. Rich cement mortar mix produces some bad results. It is advisable not to use mortars with cement component more than the above suggested standard mixes.

Care and caution is advised in the use of mortar mixtures that may harm and cause increased salt crystallization for decorative stonework or walls with frescos like reliefs or paintings.

Admixtures

It is advisable to minimize the use of admixtures in mortars, like waterproofing compounds, unless proven by tests, on old stone or masonry walls. By inhibiting thermal and moisture movement, they cause the underlying stone or masonry work to suffer the effects of heat, damp and salt migration.

Coloring

Coloring may be added to materials to achieve desired color of renders such as marble dust or white Portland cement for whitening; powdered and colored oxides, for tinting and toning, and powdered adobe or brick, for natural colors. Besides coloring renders and mortars, stone or brick powder or chips also serve as grog to minimize or compensate shrinkage upon setting of the new component.

3.0 Cleaning of Stone and Masonry Walls

Cleaning of stone and masonry work is one of the measures undertaken in active conservation work. Cleaning results in physical change for a historic building where accumulated dirt and other materials are removed. Also, the stone surface is relieved of materials that may be harmful to the stone itself. Although cleaning may not be welcomed by those who would rather see the sense and evidence of history and patina of age on the stonework, cleaning does assist in preventive conservation work.

Cleaning of historical structures should be scrupulously done so that the stone receives the least possible harm or damage. Overcleaning may result in partial loss of the stone material and diminished physical properties. Staining, vulnerability to pollutants or biological growths and deposition of soluble salts may occur (Price 1996). In this sense, it is necessary to have a basic understanding of the levels of cleaning to guide active conservation work. See Fig. 20.

Careful and prior testing and use of cleaning applications on test areas on the stone surface is necessary. This is to allow the conservator to gauge the effectiveness of the application or intervention over a period of time. Among stone and masonry cleaning techniques are mechanical cleaning, water cleaning, application of poultices, and special cleaning techniques like laser cleaning.

Cleaning is usually undertaken when there are manifestations of biological growth, surface depositions like salts, soiling and black crusts, and staining.Soiling and Surface deposits

A common problem in stone and masonry work is the amount of external soiling by dirt or surface deposits that need to be removed. These deposits may include the following: atmospheric particulates, mortar splashes and runs, encrustation, salt formations, bird deposits, paint, graffiti, iron or cuprous stains, and biological growth, which may include algae, lichens and higher plants (BS 8221-1:2000).

Salts

Crystallization of salts in stone or masonry work is one cause of deterioration. Salts that crystallize in the stone surface are known as efflorescence and those within the stone are known as cryptoflorescence. Efflorescence is unsightly but relatively harmless. However, cryptoflorescence attacks the stone from within and exerts pressure, affecting the stones strength. Prolonged cycles of crystallization within the stone may eventually cause damage to the extent of causing pulverization or powdering. Salts also affect the stones physical properties and may even enhance other causes of decay. Soluble salts attract by osmosis liquid water or water vapor, thus, increasing the critical moisture level of the stone and prevent drying of the masonry (Torraca 1988).

Common salts that are known to damage stone and masonry are sodium sulfate, sodium carbonate, magnesium sulfate, potassium carbonate, potassium sulfate, sodium chloride (common salt), potassium chloride, calcium sulfate, sodium nitrate and potassium nitrate (Honeyborne 1999). Sources for the salts mentioned include among others washing powder for clothes, washing soda for domestic cleaning, epsom salt, fresh concrete and cement-based mortar, seawater, saltpeter in meat preservatives, fertilizers and gunpowder (Honeyborne 1999).

Mechanical Cleaning

Mechanical cleaning usually involves dry brushing. Dry brushing removes loosely bound materials, dirt, and organic growth on the stone and masonry surface. It is preferable to use a soft nylon brush or an organically based one, e.g. coconut husk brush, over a steel brush, working from top to bottom of the walls. Dry brushing is effective for dry walls. For wet or damp walls, eliminate the source of wetness or dampness first before brushing; then, expose to sunlight or air to dry. If not possible, ultra-violet lamps, similar to those used in hospitals, may be used instead to dry the wet walls.

Cleaning by air abrasion or blasting uses aggregates and grits to remove surface dirt. The abrasives are projected through a nozzle using compressed air. Aggregate or grit type and size though should be determined by the nature and type of the stone surface and the toughness of dirt or crust formation. Ideally, the grits or aggregates used should be of softer material than the stone to be cleaned to avoid material loss to the stone structure. Commonly used abrasives or grits include sand, carborundum, iron slag, and even egg and nut shells for fragile surfaces (Ashurst 1999). Water may sometimes be used to cushion the impact of the abrasives on the stone. Cleaning by blasting is not especially advisable for cleaning local adobe or volcanic tuff stones.

This method may emit harmful dust and therefore operators should be especially protected with helmets and masks. Dust accumulated in the work site during blasting should always be collected and disposed at the end of the day.

Cleaning by Washing

Washing dirt from stone walls or masonry units is beneficial because it cleans away accumulated dirt. One natural source is rain water. Other good methods of washing include using water and brush, sprays, water lances and wet packs.

Ideally, water mist is sprayed from fine nozzles on the soiled face of the wall or building from a convenient distance, at regulated water pressures and at a time period that will prevent over saturation of the building. Water spray mists may be used to soften soiling in stone or masonry work.Cleaning with water lances is another washing method that uses low volume but higher pressure than the water spray mist method. This method uses tap water which is sprayed using a portable sprayer with nozzles.

For these water spray methods, the appropriate water pressure, which is determined through tests, should be used with the least possible damage to the stone so that weak jointing and parts of the stone material are not removed.

This method of washing may be used alternately with mechanical and chemical cleaning (Ashurst 1999). Manual brushing of soiling and dirt through the use of bristle brushes may be alternately done. Avoid removing soiling, debris or detritus by use of steel brushes. See Figs. 21 and 30-33.Chemical Cleaning

This type of cleaning uses chemicals to clean stonework. Hydrofluoric acid is used to clean sandstone and unpolished granite (Ashurst 1999). Other chemical agents can be used for cleaning stones like acid or alkali cleaning agents, although there is a risk of leaving some soluble salt residues in the stone. The use of other special cleaning methods, like sepiolite (clay) poultice on the stone, may assist harmful residues to dry out into the clay.

Application of biocides to kill biological growth, e.g. plants, prior to their removal may be resorted to. These may be sprayed directly on the plants, or injected by means of a horse syringe on smaller plant growths. For higher plants with bigger stems and thicker barks, it may be necessary to directly cut off the plants from the stone and masonry work.

Time is given for the biocides to take effect on the plant growths, after which, the appropriate method of clearing away the biological growths may be done, e.g. careful manual removal using knife blades, non-ferrous spatulas or soft wire bristles, or cutting them from the stonework.

Biological growths like mosses, lichens and algae may enhance the appearance of stonework but these may harm the stonework, especially acid-secreting lichens. Algal slimes may be potentially harmful especially if found to create slippery pavements. Stones with this type of biological growth are cleaned manually and later applied with suitable chemical solutions or biocides.Nonetheless, the environment is one factor for their repeated occurrence or repeated cycles of growth, in which case, regular cleaning and perhaps treatment, as may be determined, should be undertaken to prevent cycles of stone biodeterioration. See Figs. 22-25.Special Cleaning Methods

There are special methods that are used by conservators in cleaning stone and masonry works that involve the use of poultices, graffiti removal and laser cleaning.

A. Poultices

Black crust formations on stone surfaces may be removed using poultices with chemical solutions. Poultices are applied directly on the area and allowed to stand for a period of time.

Soluble salt formation on stone surfaces or efflorescence should be removed, although efforts should also be done to trace and eliminate the sources of salts. Poultices are often used to desalinate stone surfaces, using paper pulp, clay and cellulose ethers.

Biological cleaning involves the use of biological media in poultices to clean stone surfaces, as in the use anaerobic bacteria to remove black crusts formed on stone surfaces.

Clay Packs

Clay, especially sepiolite and attapulgite, has been known for its cleaning effects particularly when applied as a poultice. The clay composition sucks or lifts the soiling or crusts from the stone surface. The clay pack or poultice may be left for a few days to a considerable period of time like weeks before getting good results. Suited for cleaning sculpture and small-scale details is the Hempel biological pack. The pack contains urea, glycerol and water with sepiolite or attapulgite clay to form a paste. The paste is then applied on the pre-wetted stone surface. The pack hastens the cleaning of the stone surface by breaking down the sulfate crusts on marble and limestone. The poultice is then covered with polyethylene film to prevent air coming in contact with the pack. The paste is then removed after a considerable period of time, after which the surface is brushed and cleaned (Ashurst 1999).

The Mora Poultice

The Mora poultice is used especially for cleaning limestone and marble and has proven considerable success. The poultice constitutes a mixture of ammonium bicarbonate, sodium bicarbonate, EDTA (ethylene diaminotetraacetic acid) surfactant disinfectant, carboxymethyl cellulose and water (Ashurst 1999). See Figs. 26-29 and 34-36.

Lime Poultice

One of the traditional methods of cleaning limestone is through the use of hot lime poultice. Lime poultice is a traditional technique of applying poultice onto the wall surface to effect cleaning or softening of dirt. The poultice is applied by trowel to the pre-wetted stone surface. It is covered with wet sacking and covered with polyethylene sheet. Over a period of three weeks, the polyethylene sheet is lifted and the sacking is sprayed with water to keep the poultice damp. After the treatment period, the poultice plaster is removed with hand tools. Water sprays may be used to clean off the lime and soften the remaining dirt. Mechanical cleaning may be used then to remove softened deposits or dirt (Ashurst 1999).

Stain Removal

Old stone or masonry work may at times show staining from rusty iron or metal architectural fixtures and roof systems. For these, clay packs or poultices with chemical solutions of sodium citrate and glycerin or ammonium chloride may be applied to lighten or remove the staining.

B. Graffiti Removal

Graffiti in historic buildings may be removed through chemical removal using solvent-based paint removers, organic solvents and alkali-based removers. Mechanical procedures may also be used using pressure washing, air abrasion techniques and lasers.

On one hand, historical graffiti may be left untouched and instead protected since these provide interesting insights into the structures past.

C. Laser Cleaning

Laser cleaning does not involve actual physical contact with the stone and thus may be ideal for very delicate surfaces, although, this may not be applicable for all types of stones. A laser beam impacts on the stone surface, and the energy of beam is dissipated by the vaporization of dirt. Light is absorbed and cleaning proceeds. When there is no more dirt, light is reflected back by the clean surface (Price 1996).

One effect of laser cleaning is the yellowing of white stone surfaces because of the burning effect of laser beams. Because of the expensive cost which entails laser cleaning and its possible effects on the stone material, the conservator should also consider economy, the physical and chemical effect on the stone, and the optimum laser pulse and wavelength needed to achieve the desired level of cleanness.

4.0 Stone Consolidation

Consolidation of stone is necessary when it is determined to be weakened by deterioration and thus needs to be strengthened. It normally requires treatment of the stone material, and generally through chemical solutions. This includes penetrating the stone with a solution, binding it together and securing it in place. Consolidation aims to strengthen the stone material and prolong its life.

Lime Method

The lime method operates on the principle that if a saturated solution of calcium hydroxide is allowed to permeate the limestone, subsequent evaporation will lead to the deposition of calcium hydroxide in the stone. This will react with carbon dioxide in the air to form calcium carbonate or limestone (Price 1996, Borrelli 1999).

Lime water is a good consolidant and protective coat for masonry units made of limestone and marble. Before application, it is necessary to clean the stone and masonry work first, in which case, lime poultice may be used (Ashurst 1999). Later, the surface is prepared by brushing down and cleaning the stone.

The surface should not be too dry on application, and direct heat on a warm day should be avoided. Lime water when cool is applied thinly by brush. Four liters (1 gallon) should cover an area of approximately eighteen square meters. The surface of the stonework is washed with lime water repeatedly and the application is allowed to dry. Lime water is applied approximately 40 times over a period of several days. Lime water should not be allowed to remain on the surface but instead sponged out carefully and squeezed out in clean water.

Another method is to mist spray the stone with lime water using a pressure sprayer. This is considered better than brush application. The brush does not come in contact with the stone surface and the lime water can slowly penetrate the surface with more efficiency. Application is repeated up to forty times. With repeated mist application, each layer of application penetrates the wall. Through the lime cycle process, the limestone is strengthened (Ashurst 1999). Lime Water Preparation

Mix in 1 part lime to 7 (6-8) parts water. Place in a large container or drum. Stir the mixture from time to time for about 7 hours. Allow to stand overnight. Remove film over the lime water mixture. Lime silt will have formed by this time at the bottom of the drum. The clear lime water should be carefully drawn out from the tank to avoid mixing with the lime deposit. Use only the clear lime water solution for washing masonry surface (Peterson 1981, Ashurst 1999).

Grouting Injection in Masonry

Grouting injection can be used to improve the homogeneity and strength of weak and porous mortars of randomly-coursed masonry and of sack masonry. This method of consolidation improves the strength of masonry by filling the cavities and bonding the faces of crossing cracks.

5.0 Replacement of Stone and Masonry Units

In masonry walls or areas where stone blocks or units are found to be seriously weathered or deteriorated, replacement or substitution of the unit/s is considered to be the more appropriate solution. As much as possible, replacement stones should be geologically compatible with the old weathered stones.Replacement of Coral Blocks

In masonry work where there are voids created by detached or seriously deteriorated coral blocks, loose coral blocks available on site or from other areas can be recycled. They may be used to fabricate simulated or cast coral block or moulding substitutes.

To make simulated coral substitutes, the following materials are needed: white Portland cement; coral chips or powder prepared from small coral blocks; white sand (washed); 8mm diameter reinforcing bar or dowel and #16 G.I. tie wire (optional); masonry tools; and, plain G.I. sheet for profile template. Mix the following proportions of: 1 part white Portland cement

1 part coral chips/powder

2 parts white sand

Create new coral blocks through pre-cast fabrication.

For lightweight construction, styropore core, fiberglass-reinforced or wire-mesh-reinforced precast units can be used. The mortar can be added with polymer admixture in case of outdoor application. There are many fabricators offering this type of lightweight precast construction and cast-in-place construction.

For decorative applications in the interiors, imitation coral units can be done in gypsum (Plaster of Paris) simulations; however, the units should be fired in ceramic kilns at about 1300 degrees centigrade for 6-8 hours for permanent setting.

6.0 Repointing of Masonry Joints

Repointing is a remedial treatment with the aim of sealing gaps, filling small cavities and replacing decayed mortar joints. It is the method of introducing new mortars with the use of a pointing device or pointing iron. A well-repointed masonry joint prevents the entrapment of moisture, and the accumulation of dirt and organic materials that contribute to the disruptive growth of wind-borne plants.

Masonry joints are cleaned and cut to the required depth and never to a depth less than their width. The stone face and block should be left clean for maximum contact with new mortar or new pointing. As much as possible, maintain original joint width in repointing. See Figs. 37 and 38. Brick chips, shells, coral chips or other materials for garreting or galleting (spacer block between stones for good bonding alignment) may be used.

C. Preventive Conservation for Stone and Masonry Buildings

After restoration or conservation, the conservator or restorer is faced with the possible reoccurrence of deterioration. Preventive conservation techniques should be undertaken in this case. This may include among others surface treatments or protections like periodic replastering of the masonry surface, control of rainwater dispersal and water drainage, building protection from bats and birds that roost or inhabit the structure and deposit excreta on stone pavements, ledges and walls, and regular cleaning, repair, and maintenance of the structure.Surface Treatments

Surface coatings on stone are resorted to as a protection against possible future deterioration. Such surface treatments may include water repellents, emulsions, barriers against air pollution, salt crystallization inhibitors, sulfatation of calcium carbonate inhibitors, lime washing as protective coating, and biocides.

The real test on whether surface treatments work is their application and natural exposure over a period of time. This test may be carried out in situ or at small test samples brought to the laboratory. Their long-term performance and effects on the stone structure may only be gauged over time (Price 1996).Storm Water Drainage and Dispersal

Excessive wetting of stone and masonry walls or structures cause several damages such as weakening, formation of surface vegetation, encrustation and erosion, and crack development.

Preventive conservation measures may include repair of water dispersal systems like the provision of extended roof downspouts, improvement of area drainage system (drain away from the protected structure), removal of plants or plant boxes along the stone or masonry wall, restoration of the roof sweep if applicable, provision of roof gutter or its repair, provision of perforated pipe drainage system on the sub-floor and provision of weep holes at retaining walls. See Fig 39. For ledges or exposed wall surfaces subjected to dispersed rainwater, caps in the form of terracotta or clay tiles may be introduced to minimize water seepage or erosion.Protection from Bird/Bat Droppings

Bird and bat droppings are not only unsightly but potentially harmful to stone. Nets may be improvised or installed to control entry of birds and bats in buildings, gel and spikes laid out in strip form to prevent bird settling, low voltage wires at facades or simple stainless steel wires stretched along ledges to prevent bird roosting. See Figs. 41 and 42.

Repair, Maintenance and Surface Protection

Regular repair and maintenance of historic buildings should be an important component of any conservation program. When there is sign of deterioration, immediate repairs or treatments should be made. This is to prevent further aggravation of the stage or level of deterioration.Part of maintenance work is checking the condition of plasters or renders and determining whether they should be stabilized, treated or redone. Plasters or renders were provided in the past for the very purpose of protecting the stone walls of structures from the harsh exposure to elements. They were intended as skins for protection of structures. Since plasters also act as sacrificial renders or protective layer to the stone or masonry surface, they should be periodically renewed when it has deteriorated or lost much of its functionality.

Restoration works in the Philippines beginning in the mid-1970s promoted removal of the plaster from historic walls made up of tuff or adobe, thus, exposing the stones to weathering agents. Exposed adobe deteriorated faster than those that were protected by plaster. Water vapor and rain were discovered to be the common causes of tuff weathering which may come in the form of pulverization or erosion of the stone material (Paterno and Charola 2000).

On the other hand, periodic maintenance and repair by replastering contribute to the durability of the underlying stonework or brickwork. If only a small portion of the original plaster has flaked off, it should not be removed but stabilized instead. Old plaster can be consolidated by appropriate grouting mixture or solution. Plasters must maintain a certain degree of permeability in order to allow the surface aeration of the masonry. As a note of caution, it is advisable not to apply paint and acrylic emulsion on adobe (tuff) and other stone surfaces. The application of such will only hasten the deterioration of organic stonework, since the applied solution may create an impermeable film or coat that could lead into entrapped moisture in the walls corework.

Oversaturation and dampness of walls may result into stone and mortar decay and stresses can cause the collapse or detachment of the facework/plaster from the masonry corework. In some cases, a very strong impermeable cement-based plaster may cause detachment of the new plasterwork from the masonry wall. New plasters to be applied on the structure should highly consider its main feature as a porous protective render that would allow water accessibility in liquid and vapor forms (Torraca 1988).

Plasters in historic buildings should be treated cautiously, though. They are historical references and may contain past information including those about the structure and its history, e.g. previous paint renders, polychromy signs, and historical graffiti. These plaster layers should be preserved as much as possible.

D. Structural Restoration of Stone and Masonry Walls

Structural behavior of masonry buildings is dependent mainly on the materials used, the shape and dimensions of the structure, the connections between different elements and the boundary conditions (Croci 1998). Structural damage is usually attributed to the increase in mechanical actions involving dead loads, soil settlements, temperature, earthquake, wind, etc. or to the reduction of structural efficiency caused by physico-chemical actions of weathering and deterioration. Damages are likely to occur when alteration is uncontrolled which usually take the form of the following:

i) Previous soil settlements and earthquake that have weakened connections and created permanent deformations;

ii) Increasing dimensions of wall openings, niches and chases that induces cracks, deformation and crushing effect;

iii) Elimination of structural elements, e.g. removal of walls, pillars, lintels;

iv) Removal of alterations to the supports in structures of producing thrust;

v) Additional loadings; and

vi) Excavations close to the foundations.

Masonry is a compression-resistant structure. A thorough examination of structural damage is very important prior to any structural intervention or remedial treatment as some deformations are related to the structural behavior and the actions that may have caused it. Visible signs of structural damage include the following: (i) cracks in materials not resistant to tensile stress; (ii) crushing of compressed elements marked by swelling, flaking and crumbling; (iii) permanent deformations linked to the effects of bending induced by off-center loads and thrusts (Croci 1998).

Restoration of masonry walls will almost always consider the presence of cracks and indications of leaning and deformations. Regarding cracks, it is important to examine and analyze the type (superficial or through/continuous), the extent (size and form) and nature (structural or non-structural).

Cracks occur in old stone and masonry structures as a result of many factors. Cracks usually appear at openings and start at the weak points. Cracks may be just surface cracks or through (structural) cracks which appear on both sides of the wall.

The nature of cracks can tell what the causes are, e.g. a diagonal crack may have been caused by ground erosion; and, a vertical crack along perpendicular walls may have been caused by torsion due to an earthquake. It is advisable to consult experts if structural cracks occur in historic buildings.

The restorer should take note of the structural behavior, fabric, and status of the cracks (active or passive). If the crack is observed active, an improvised monitoring device or glass telltale may be installed to check its behavior.

A method to rejoin wall sections separated by cracks is by grouting-and-doweling. It may also be necessary to consolidate the foundation first before correcting the wall defects.

New structures may be used to rejoin and strengthen the separated wall components. One system is by inserting or embedding a supporting structural framework system.

The diagnosis and safety evaluation of damages in structures and decay in materials often involve direct observation of the building, historical research and mathematical models, sometimes with the aid of laboratory tests and a monitoring system. These should precede decisions concerning the structural restoration of masonry. It is also best to consider integrating interventions that could best achieve current safety standards and preserve the historic value of the building.

Glossary

Admixture - added substance that modifies properties such as the workability of the mortar mixture that cannot be obtained using basic binders (i.e. casein, oils, synthetic resins, water reducers, setting time retardants).Adobe - a Spanish word for sun-dried brick. In the Philippines, it refers to a type of stone of volcanic tuff origin commonly used as building block; it varies in composition and color depending on its geographical location.Aggregate - material added to binders to prepare mortar, which can be natural (e.g. sand, crushed stones) or artificial (e.g. crushed bricks, pottery sherds).Air pollution - a state of atmospheric contamination by obnoxious gases.

Alteration - change in the material not necessarily signifying a negative effect in its properties.

Binder - natural (inorganic) and/or artificial material that, when mixed with water, permits the preparation of a plastic mixture that hardens to form a solid mass; a material, which binds sand particles or crushed stones together to obtain mortars (i.e. gypsum, lime, cement, etc.); common binders include clay, gypsum, lime, hydraulic lime and Portland cement..

Biocides - chemical treatments that aim to kills, inhibits or controls biological growth.

Cement - a combination of powdered calcined limestone and clay mixed with water and an aggregate to make mortar or concrete.

Charter of Venice (May 1, 1964) - defines the recommendations of international restorers and lays down the principles guiding the preservation and restoration of monuments and sites based on international cooperation. It became the solid foundation of the International Charter for the Conservation and Restoration of Monuments and Sites that enjoined all the basic principles and recommendations including researches and studies made by the international movements or organizations such as the UNESCO, ICOM, ICCROM and the European Council. In 1981, in Rome, amendments were integrated to redefine and clarify the provisions that were misinterpreted by the different restorers in their respective applications.

Chemical Cleaning - a cleaning process which applies chemical solution on the surface to be cleaned to remove or extract the unwanted elements or superficials; an initial stage of intervention in preparation for the consolidation of the material.

Coating - a layer of material applied to a surface to decorate, preserve, protect, seal, or smooth.

Conservation - an action taken to prevent or at least to slow down decay. It embraces all acts that prolong the life of cultural and natural heritage, the object being to present to those who use and look at historic buildings with wonder the artistic and human messages that such building possesses. The minimum effective action is always the best; if possible, the action should be reversible and not prejudicial to future interventions. In objects, conservation would include stabilization of the constituent materials of the artifact and removal of damaging substances; and, elimination or at least reduction of the sources of decay linked to the environment.Consolidant - a chemical solution that is applied to a deteriorating material in order to restore its stability and provide a stop to its deterioration.

Consolidation - an act of direct intervention or preservation to prevent, stop or retard deterioration; it is the physical addition or application of adhesive or supportive materials into the actual fabric of the monument.

Cryptflorescence - accumulation or crystallization of salts within the stone material; also called as subflorescence.Crystallization - a process of transformation or solidification of a chemical element, a chemical compound, or a mixture caused by chemical reactions induced by weather and exposure to external elements, thus affecting the material or structure where this transformation has undertaken.

Dampness - a state of being slightly or moderately wet.

Decay - gradual decline in strength or soundness; a wasting or wearing away; rot.

Deterioration - change in the material signifying negative effects in its properties.

Detritus - fragments formed by the disintegration of rocks or stones.

Dirt - a soiling substance.

Efflorescence - deposit of soluble salts, commonly white, on the surface of stone, masonry or plaster caused by salt migration to the surface as a result of evaporation.

Graffiti - (plural of the Italian word graffito meaning a scratch) crude inscription or drawing found on rocks or walls.

Grog - recycled material usually in chip or powder form, which is mixed with mortar or plaster, the purpose of which is to reduce shrinkage when setting.

Epoxy - a class of synthetic, thermosetting resins which produce tough, hard, chemical-resistant coatings and excellent adhesives.Galleting - the insertion of stone chips into the joints of rough masonry to reduce the amount of mortar required, to wedge larger stones in position, or to add detail to the appearance; pieces of tile used to provide a suitable bed for ridge tile or hip tile; the pressing in of pebbles, small stones or flakes of flint into soft mortar to tighten the joints of coarse masonry and protect them against erosion.

Graffiti - pl. graffito, Italian; crude inscription or drawing found on rocks or walls.

Grouting - filling the voids in or between aggregate, block, or tile with grout; the process by which grout is injected, i.e., hand grouting, gravity grouting, mechanical grouting by pump or air pressure, and vacuum grouting.

Blasting (Grit blasting/Air abrasion) - grit blasting as a means of mechanical cleaning.

Half-restoration - partial restoration which is intended to create balance between interpretation and authenticity.

Hempel biological pack - poultice made up of urea, glycerol and water with clay, e.g. sepiolite, and then applied on the pre-wetted stone surface, as invented by K. Hempel.

Humidity - water vapor within a given space or environment.

Hydrated Lime - [CA(OH)2] slaked lime in powder form; obtained by treating quicklime (CaO) with enough water to combine chemically to form calcium hydroxide.Hydraulic Lime - a dry product obtained by burning limestone containing silica and alumina at a temperature above 900C.Intervention - an anglicized use of a Latin word meaning to interfere with the state of an object of cultural property in order to conserve it. The minimum intervention is the best. Any intervention, however, must be reversible.

Lime - anhydrous lime, burnt lime, calcium oxide, caustic lime, caustic lime, common lime, quicklime - a white or graying caustic substance; usually obtained by heating limestone or marble at a high temperature, leaving a residue; when water is added, a lime putty formed, called hydrated lime or slaked lime, which is used in mortars and cements.

Lime-cement-sand mortar - hydrated lime, lime putty, or slaked lime mixed with Portland cement and sand; forms a cement mortar used in masonry and in Portland cement plaster (stucco).

Lime mortar - also air-setting mortar; mortar made by mixing lime putty and sand; it hardens only in the presence of air due to carbonation (reaction with CO2; seldom used because of its slow hardening.Lime plaster - a base-coat plaster consisting of lime and aggregate.

Lime putty - [CA(OH)2] slaked lime in plastic form; quicklime slaked with an excess of water and kept covered (with water) in a pit for at least two months.Limestone - rock of sedimentary origin composed principally of calcite or dolomite or both; used as building stone or crushed-stone aggregate or burnt to produce lime.

Lime wash - syn. White wash; slaked lime diluted with water, and used as a house paint for exteriors and interiors or as preparatory layer for frescos; obtained by adding a large amount of water to slaked quicklime or hydrated lime and applied on external surfaces.Lime water - saturated transparent solution of calcium hydroxid, formed on top of lime putty in the pit; sometimes used in fresco technique as medium for pigments.Masonry - the art of shaping, arranging, and uniting stone, brick building blocks, etc., to form walls and other parts of a building; art or trade of building in stone, universally practiced since ancient times.

Mortar - a plastic mixture of cementitious materials (such as plaster, cement, or lime) with water and a fine aggregate (such as sand); can be troweled in the plastic state; the mixture may contain masonry cement with lime (and often other admixtures) to increase its plasticity and durability; a compound of lime and/or cement and sand, mixed with water and used as jointing or bonding in brickwork.

Moisture - water or other liquid causing a slight wetness or dampness.

Mechanical cleaning- cleaning with the aid of manual tools, such as bristle brush, rag, scraper, spatula, air abrasion/grit blasting equipment.

Mortar - a combination of binder and fillers such as sand, crushed stones and water to form a paste; a building material prepared by mixing one or more inorganic binder (lime, clay, gypsum, cement) with inorganic and/or organic fillers (inerts, hydraulic fillers, fibrous materials); in masonry, it is used to refer to the bonding material of stones and bricks.Plaster - a surface material of a wall or building which has been applied as a plastic mass and has set by drying, carbonatation or hydration. Classification of plaster is referred to by the main binding material, e.g. lime plaster, clay plaster, mud plaster, gypsum plaster, cement plaster.Pointing - the process of filling the masonry joints from the face; refers to the final treatment of joints by the troweling of mortar or a putty-like filler into the joints; the material with which the joints are filled. See repointing.Polychromy - the condition or practice of applying more than one color on a surface.

Poultice - an absorbent paste applied to masonry to draw out stains.

Portland cement - a type of hydraulic cement made of finely pulverizing the clinker produced by calcining to incipient fusion a mixture of argillaceous and calcareous materials.

Pozzolana - a volcanic ash, originally found near area of Pozzuoli (Puteoli) in Italy. This was the main ingredient of the early Roman cement. Pozzolan cement is the modern counterpart of the Roman cement, having good hydraulic qualities, although strictly requiring just enough water content to attain its almost dry plastic form that is best for its application.

Preventive maintenance - a good program of maintenance that is periodically (routine) undertaken so that corrections or minor repairs are instituted to prevent spread of or larger scale defects.

Render - coat of plaster on the surface of a wall; refers also to a rough finish or protective coat.

Repointing - the removal of mortar from between the joints of masonry units and the replacing of it with new mortar. Restoration - the conservation of the material of the monument; action taken to correct deterioration and alterations; activity aimed at improving the legibility and the aesthetic presentation of an artifact. The main aim of restoration is preservation. Putting back a structure to its original form is secondary. Nothing can be put back to its originality (original state).

Rust - a substance, usually in powder form, of light brownish red color, accumulating on the face of steel or iron as a result of oxidation, that ultimately weakens or destroys the steel or iron on which it forms.

Saturation - the condition under which air at a given temperature and pressure holds the maximum amount of water vapor without causing precipitation.

Sepiolite - clay derived from volcanic ash, consisting of a naturally hydrated silicate of magnesium, used for chain-like structure similar to attapulgite but with wider internal laths.

Slaked lime - [CA(OH)2] calcium hydroxide formed by the hydration of quick lime; two types of slaked lime are: hydrated lime in powder form and lime putty.Stone - rock selected or processed by shaping, cutting or sizing for building or other use.Structural framework system - a system of interconnected columns, beams, ties, braces, and/or corbels that can stabilize the edifice and prevent future leaning and other damages).

Weathering - any action of the weather on natural and artificial materials

REFERENCES AND SUGGESTED READING

BooksAshurst, John and Dimes, Francis G., eds.

1999 Conservation of Building & Decorative Stone. Oxford: Butterworth-Heinemann.1983 Mortars, Plasters and Renders in Conservation. Ecclesiastical Architects and Surveyors Association.

Blair, Emma Helen and Robertson, James Alexander

1903The Philippine Islands (1493-1898). Cleveland: Arthur Clark Co. Borrelli, Ernesto

1999 ARC Laboratory Handbook. Binders. Rome: ICCROM.

Calvani, Angelo

U.d.Uso di Nuove Tecnologie nel Restauro Architettonico. Multigrafica Editrice.

Caneva, Giulia, Nugari, Maria Pia and Salvadori, Ornella

1991 Biology in the Conservation of Works of Art. Rome: ICCROM.

1983Crafts Council Conservation Science Teaching Series. Science for Conservators Book 2. Cleaning. London: Crafts Council.

Croci. Giorgio1998The conservation and structural restoration of architectural heritage. Great Britain: Computational Mechanical Publications.Davey, Norman

1971A History of Building Materials. London: Phoenix House.DOssat, Guglielmo De Angelis

1982 Guide to the Methodological Study of Monuments and Causes of Their Deterioration. Rome: ICCROM/Faculty of Architecture University of Rome.Fassina, Vasco, ed.

2000Proceedings of the 9th International Congress on Deterioration and Conservation of Stone. Amsterdam: Elsevier.

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1994 Conservation of Historic Buildings, rev. ed. Oxford: Butterworth- Heinemann.Jackson, Albert and Day, David.

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(Venice Charter 1964)PREAMBLEImbued with a message from the past, the historic monuments of generations of people remain to the present day as living witnesses of their age-old traditions. People are becoming more and more conscious of the unity of human values and regard ancient monuments as a common heritage. The common responsibility to safeguard them for future generations is recognized. It is our duty to hand them on in the full richness of their authenticity.

It is essential that the principles guiding the preservation and restoration of ancient buildings should be agreed and be laid down on an international basis, with each country being responsible for applying the plan within the framework of its own culture and traditions.

By defining these basic principles for the first time, the Athens Charter of 1931 contributed towards the development of an extensive international movement which has assumed concrete form in national documents, in the work of ICOM and UNESCO and in the establishment by the latter of the International Centre for the Study of the Preservation and the Restoration of Cultural Property. Increasing awareness and critical study have been brought to bear on problems which have continually become more complex and varied; now the time has come to examine the Charter afresh in order to make a thorough study of the principles involved and to enlarge its scope in a new document.

Accordingly, the IInd International Congress of Architects and Technicians of Historic Monuments, which met in Venice from May 25th to 31st 1964, approved the following text:

DEFINITIONSARTICLE 1. The concept of an historic monument embraces not only the single architectural work but also the urban or rural setting in which is found the evidence of a particular civilization, a significant development or an historic event. This applies not only to great works of art but also to more modest works of the past which have acquired cultural significance with the passing of time.

ARTICLE 2. The conservation and restoration of monuments must have recourse to all the sciences and techniques which can contribute to the study and safeguarding of the architectural heritage.

AIMARTICLE 3. The intention in conserving and restoring monuments is to safeguard them no less as works of art than as historical evidence. CONSERVATIONARTICLE 4. It is essential to the conservation of monuments that they be maintained on a permanent basis.

ARTICLE 5. The conservation of monuments is always facilitated by making use of them for some socially useful purpose. Such use is therefore desirable but it must not change the lay-out or decoration of the building. It is within these limits only that modifications demanded by a change of function should be envisaged and may be permitted.

ARTICLE 6. The conservation of a monument implies preserving a setting which is not out of scale. Wherever the traditional setting exists, it must be kept. No new construction, demolition or modification which would alter the relations of mass and color must be allowed.

ARTICLE 7. A monument is inseparable from the history to which it bears witness and from the setting in which it occurs. The moving of all or part of a monument cannot be allowed except where the safeguarding of that monument demands it or where it is justified by national or international interest of paramount importance.

ARTICLE 8. Items of sculpture, painting or decoration which form an integral part of a monument may only be removed from it if this is the sole means of ensuring their preservation.

RESTORATIONARTICLE 9. The process of restoration is a highly specialized operation. Its aim is to preserve and reveal the aesthetic and historic value of the monument and is based on respect for original material and authentic documents. It must stop at the point where conjecture begins, and in this case moreover any extra work which is indispensable must be distinct from the architectural composition and must bear a contemporary stamp. The restoration in any case must be preceded and followed by an archaeological and historical study of the monument.

ARTICLE 10. Where traditional techniques prove inadequate, the consolidation of a monument can be achieved by the use of any modem technique for conservation and construction, the efficacy of which has been shown by scientific data and proved by experience.

ARTICLE 11. The valid contributions of all periods to the building of a monument must be respected, since unity of style is not the aim of a restoration. When a building includes the superimposed work of different periods, the revealing of the underlying state can only be justified in exceptional circumstances and when what is removed is of little interest and the material which is brought to light is of great historical, archaeological or aesthetic value, and its state of preservation good enough to justify the action. Evaluation of the importance of the elements involved and the decision as to what may be destroyed cannot rest solely on the individual in charge of the work.

ARTICLE 12. Replacements of missing parts must integrate harmoniously with the whole, but at the same time must be distinguishable from the original so that restoration does not falsify the artistic or historic evidence.

ARTICLE 13. Additions cannot be allowed except in so far as they do not detract from the interesting parts of the building, its traditional setting, the balance of its composition and its relation with its surroundings. HISTORIC SITES

ARTICLE 14. The sites of monuments must be the object of special care in order to safeguard their integrity and ensure that they are cleared and presented in a seemly manner. The work of conservation and restoration carried out in such places should be inspired by the principles set forth in the foregoing articles.

EXCAVATIONS

ARTICLE 15. Excavations should be carried out in accordance with scientific standards and the recommendation defining international principles to be applied in the case of archaeological excavation adopted by UNESCO in 1956.

Ruins must be maintained and measures necessary for the permanent conservation and protection of architectural features and of objects discovered must be taken. Furthermore, every means must be taken to facilitate the understanding of the monument and to reveal it without ever distorting its meaning.

All reconstruction work should however be ruled out "a priori." Only anastylosis, that is to say, the reassembling of existing but dismembered parts can be permitted. The material used for integration should always be recognizable and its use should be the least that will ensure the conservation of a monument and the reinstatement of its form. PUBLICATIONARTICLE 16. In all works of preservation, restoration or excavation, there should always be precise documentation in the form of analytical and critical reports, illustrated with drawings and photographs. Every stage of the work of clearing, consolidation, rearrangement and integration, as well as technical and formal features identified during the course of the work, should be included. This record should be placed in the archives of a public institution and made available to research workers. It is recommended that the report should be published.

The following persons took part in the work of the Committee for drafting the International Charter for the Conservation and Restoration of Monuments:

Piero Gazzola (Italy), ChairmanRaymond Lemaire (Belgium), ReporterJose Bassegoda-Nonell (Spain)Luis Benavente (Portugal)Djurdje Boskovic (Yugoslavia)Hiroshi Daifuku (UNESCO)P.L de Vrieze (Netherlands)Harald Langberg (Demmark)Mario Matteucci (Italy)Jean Merlet (France)Carlos Flores Marini (Mexico)Roberto Pane (Italy)S.C.J. Pavel (Czechoslovakia)Paul Philippot (ICCROM)Victor Pimentel (Peru)Harold Plenderleith (ICCROM)Deoclecio Redig de Campos (Vatican)Jean Sonnier (France)Francois Sorlin (France)Eustathios Stikas (Greece)Mrs. Gertrud Tripp (Austria)Jan Zachwatovicz (Poland)Mustafa S. Zbiss (Tunisia)

Annex 2

ICOMOS PROCEEDINGS OF THE 6TH GENERAL ASSEMBLY AND OF THE INTERNATIONAL SYMPOSIUM NO FUTURE WITHOUT A PAST HELD IN ROME, BARI, FLORENCE AND VERONA FROM 25 TO 30 MAY 1981

ON THE

INTERNATIONAL CHARTER FOR THE CONSERVATION AND RESTORATION OF MONUMENTS AND SITES

ICOMOS, in conclusion of the proceedings of the 6th General Assembly and of the International Symposium "No future without a past" held in Rome, Bari, Florence and Verona from 25 to 30 May 1981:

1) Formally recalls and confirms the following introductory text to the "International Charter for the conservation and restoration of monuments and sites" adopted in Venice on 31 May 1964:

Imbued with a message from the past, the historic monuments of generations of people remain to the present day as living witnesses of their age-old traditions. People are becoming more and more conscious of the unity of human values and regard ancient monuments as a common heritage. The common responsibili