Decorative Architectural Ironwork

Ali Davey Head of Technical Outreach & Education

Historic Scotland Conservation Group

Evolution : Jean Tijou

1693

Carron Ironworks, 1759 - 1982

The Adam Brothers

Carron Ironworks

Why Scotland?

Black Band Ironstone discovered by David Mushet in 1801

Hot Blast invented by James Beaumont Neilson in 1828

Walter MacFarlane & Co Ltd, Saracen Foundry (1850 – 1967)

Drinking Fountains

No. 8

No. 20

No. 21

Fountains & monuments

Buildings

Ca’ D’Oro, Gordon St, Glasgow (1872)Designed by John Honeyman

George Smith & Co 1858 – c.1899

Conservation and Repair

Blast Furnace

Grey Iron Wrought Iron

•Good in compression•Bad in tension•Brittle•Cheaper to produce en masse

•Poor in compression•Good in tension•Expensive to produce en masse

Cast iron

• Higher in carbon (2-4%)• Crystalline• Hard• Brittle• Shaped by casting • Strong compression• Weaker in tension• Good corrosion resistance

Recognising cast iron

• Shaped by casting• Visible mould line• Tapering edges• No undercutting

• Identical, repeating elements• Assembly

• Lugs and flanges • Panels slotted into of columns and stanchions• Bolts• Elements such as finials leaded on

Wrought iron

• Low in carbon (<0.2%)• Contains strands of slag• Fibrous • Malleable• Ductile• Shaped by hammering• Strong in tension • Good corrosion resistance

Iron Ore

Wrought Iron

Stainless Steel

Mild Steel

Cast Iron

OxidationReduction Processing

Oxygen driven off Corrosion

Electron Gain Electron Loss

Electrochemical Series

ZincAluminiumWrought ironCast iron316, 317 Stainless SteelAluminium bronzeLeadNickelBrassCopperManganese bronze, Tin bronzeNickel silver430 Stainless steelNickel, aluminium, bronze (CA 630, 632)316, 317 Stainless steelSilverTitaniumGoldPlatinum

Metals lower on the list will corrode sacrificially

for metals higher on the list

Fixings

History & Construction - Understanding the structure

Research

Assessment & recording - coatings

Repairs – planning and specification

The right facilities

The right skills

Give the contractor a chance !

Walter MacFarlane & Co, Saracen Foundry Spandrel Pattern No 51

Archive Pattern Drawing – digitised for CNC

CNC and pattern making

Cast Iron : the contentious bit....

Repair techniques

•Stitching•Plating•Pinning•Welding•Epoxy

Alternative materials

Cast iron

•Ductile iron (SG iron)•Steel•Aluminium•Bronze

Wrought iron

•Mild steel•Pure iron•Stainless steel

Zinc Phosphate 1 60 micronsZinc Phosphate 2 60 micronsMicaceous Iron Oxide 55 micronsGloss finish 1 35 micronsGloss finish 2 25 micronsTotal DFT 230 microns

The finishing touches are important!