pH, Conductivity and Offset Printing - University of Houstonsites.tech.uh.edu/digitalmedia/materials/3252/Fountain_Solution.pdf · pH, Conductivity and Offset Printing 2 Pressroom

pH, Conductivity and Offset Printing 1

2/26/02Pressroom Chemistry1

pH, ConductivitypH, Conductivityandand

Offset PrintingOffset Printing

EuGene Van Roy


IntroductionIntroduction

! At heart, lithography is a chemical process withpotential for many variables which may affectproduction and the quality of offset printing.

! Of the many facets of offset printing perhapsnone is as prone to variation as fountain solution,but while the cause and nature of these variationsmay seem complicated, controlling them isrelatively simple.



AgendaAgenda

! What is the purpose of fountain solution?! How important is the water source?! What is pH, and determining pH?! What is conductivity and how do we

measure conductivity?! Problems caused by incorrectly mixed

fountain solution?


OverviewOverview

! In 1796, Alois Senefelder applied an oiltype ink on stone, and found that wateradhered to the non-image area only.With trial and time, more sophisticatedmethods were developed. This was doneby using chemicals in the water, inconjunction with metal plates which haveoleophilic (ink receptive) and hydrophilic(water receptive) surfaces.



OverviewOverview

! In Senefelder�s day hewent to the well, got abucket of water, andwas ready to go. Ifthings were only thatsimple. We will lookat how we can makethe complex variablesof fountain solutionsimple.


What is the purpose ofWhat is the purpose ofFountain Solution?Fountain Solution?



Fountain SolutionFountain Solution

! The dampening of the offset plate is oneof the most critical factors in quality offsetprinting.

! A solution of a fountain concentrate mixedwith water is created that performs severalessential functions on press.

! The most important of these is the wettingand desensitizing of the non-image area ofthe plate.



! Fountain solution lubricates the plate andblanket, helping to reduce image wear andprolong plate life.

! Fountain solution cools and helps tomaintain the working properties of ink.

! Fountain solution aids in proper blanketrelease, which reduces piling on theblanket.




! The pH and conductivity of the fountainsolution are of major importance if thefountain solution is to properly fulfill it�sfunction of preventing plate non-imageareas from accepting ink.

! Mixing solution should be done on a dailybasis for small duplicators, and tested dailyon large presses with holding tanks.

! The fresher, the better!


Fountain Solution ComponentsFountain Solution Components

! Most fountain solutions are made up offive basic ingredients and water.

"Acid.

"A wetting agent (surfactants).

"Plate conditioners (chemical salts).

"Gum arabic.

"A buffering agent.




! Acid.

"Usually a mild acid, which helps reducethe pH and keeps the image areasensitive to ink and the non-image areamore sensitive to water.


Fountain Solution ComponentsFountain Solution Components! A wetting agent.

"Sometimes referred to as surfactants,these are used to lower the surfacetension of the water allowing it tomaintain the wetting ability of thefountain solution in the non-image areas,while allowing you to run less water.Common agents used are: IsopropylAlcohol, Glycerin, and various Glycols.




! Plate conditioners (chemical salts).

"These are used to minimize thecorrosive action of the acid on thesurface of an aluminum or metal plate.This is designed to increase the printquality and to extend the life of theplates. Most solutions also contain anti-foaming and anti-fungus ingredients.


Fountain Solution ComponentsFountain Solution Components! Gum arabic.

"Gum arabic has already been addedto most fountain solution concentratesmade today. It�s function is to adhere tothe plate�s non-image area and protectit from accepting ink. Gum also servesto protect the plate from humidity andchemical attack during press stops.



Fountain Solution ComponentsFountain Solution Components! A buffering agent.

"A substance capable of neutralizing acids andbases in solutions and thereby maintaining theacidity or alkalinity level of the solution.

"Keeps the pH constant or within a certainrange regardless of how much acid is added.

"Neutralizes the effects of paper, inks, gases,and humidity.


Fountain Solution ComponentsFountain Solution Components! Alcohol in dampening solutions.

"Alcohol is added to the fountain solution asa surfactant. It makes the water wetter. Byreducing the surface tension of the waterthe water will spread out to a thinner film.



Fountain Solution ComponentsFountain Solution Components! Alcohol in dampening solutions.

"Isopropyl alcohol is a volatile organiccompound. As a VOC alcohol pollutes ourpressroom and our environment. It isrecommended to use alcohol substitutes.

How importantHow importantis theis theWaterWatersource?source?



WaterWater

! Since approximately 98% of a workingfountain solution is water, being aware ofyour water condition is of vital importance.

! Water can be either hard or soft, acid oralkaline. In fact, water quality can varyseasonally, monthly, weekly, or even daily.


WaterWater

! Understand that tap water can be a variablewhen used in fountain solution becausesome minerals and chemicals in the watermay not be compatible with the chemicalsin the fountain solution concentrate.



WaterWater

! There are three stable substitutes for tapwater: De-ionized, Distilled, and ReverseOsmosis water.


WaterWater

! De-ionization, or the demineralizationprocess.

"A complex chemical process that uses twoion exchange resins to remove mineralsfrom water. The cost of this method isconsiderably less than the cost of producingdistilled water.


WaterWater

De-ionization, orDemineralizationunit


WaterWater

! Distilled water."Produced in a laboratory by boiling ordinary

tap water in a water still. The steam that risesfrom the boiling water is almost free of themineral matter present in the tap water. Thesteam is fed through condenser coils whereit is converted into liquid, distilled water.Some fountain solutions do not work wellwith distilled water.


WaterWater

DistilledWaterUnit


WaterWater

! Reverse Osmosis water."The best method of water purification. In

this process the water is filtered through amembrane to remove most of the positiveand negative ions, un-ionized dissolved solids(sugars), suspended matter, and bacterialeaving only pure water.

"Sometimes referred to as �RO water�.


WaterWater

ReverseReverseOsmosisOsmosisUnit.Unit.


WaterWater

! What is Hard Water?



Hard Water Is:Hard Water Is:

"Tap water is rarely pure.

"Ions associated with minerals and inorganiccompounds in water make it �hard�.

"Through formation of oleaginous (oily) soaps,hard water can play havoc with pressoperations (roller stripping, halftone fill-in).

"Water hardness is rated in terms of totalconcentration of calcium carbonate ions.


WaterWater! How do we evaluate water hardness?



We evaluate water hardness by:We evaluate water hardness by:

"Water hardness usually is indicated in partsper million (PPM) (or milligrams pre liter(mg/l) or grains/gallon) of calcium carbonate.

"Water hardness varies from locality tolocality.

"The best source for determining waterhardness is the local water company.

"Water hardness can be estimated by using aconductivity meter.


We evaluate water hardness by:We evaluate water hardness by:


WaterWaterSoftener.Softener.


WaterWater! What is water alkalinity?



Water alkalinity is:Water alkalinity is:

"Alkalinity neutralizes acids.

"Tap water with high levels of alkalinity aremost common in areas with limestone deposits.

"Alkalinity is measured and expressed in PPM,mg/l or grains/gallon.

"In areas with alkaline water, alkalinity is moreimportant than water hardness becauseexcessive levels shift pH towards neutral.


What is pH?What is pH?



What is pH? (History)What is pH? (History)

! For those who wonder how the term pHcame by its odd spelling, the Romansknew pH as �potentia hydrogenii,�or �potential for Hydrogen,� and thusthe small �p� and capital �H�.

! All the press operator really needs toknow about pH is that it is a measure ofthe degree of acidity or alkalinity offountain solution.


What is the pH Scale?What is the pH Scale?

" The pH scale runs from 0 to 14.0." 7.0, the mid-point on the pH scale, is neutral." A solution with a pH of less than 7.0 is acid. A

solution with a pH of more than 7.0 is alkaline(base).

" A whole-number change on the pH scalerepresents a tenfold change in pH. Smalldifferences on the scale, in practical terms,may be quite large.





" Each whole number on the pH scale representsa tenfold change in acidity or alkalinity.

" A solution at (pH 5.0 is 10 times more acidicthan a pH 6.0) and a solution at (pH 4.0 is 100times more acidic than a pH 6.0).

" A solution at (pH 9.0 is 10 times more alkalinethan a pH 8.0) and a solution at (pH 10.0 is 100times more alkaline than a pH 8.0).



Determining pH.Determining pH.



" There are two basic methods for checkingpH in the industry: with chemically-coatedindicator papers (strips), and withelectronic pH meters.

" Indicator papers and strips tend to beinaccurate.

" Battery-operated, portable pH meters arereliable and easy to use.




" Ink-makers recommend a fountain pHof 4.5 � 5.0 for optimal performance.

" Certain duplicators, using paper plates,may require a slightly lower pH.

" Higher pH readings may cause scummingand toning, whereas pH readings of lessthan 4.0 may retard or inactivate inkdrying by locking up the catalytic dryersin the ink.


Determining pH. (Buffering)Determining pH. (Buffering)

" Without getting over-technical, buffersare chemicals that are used in fountainconcentrates to help stabilize the pHlevel of the mixed solution.

" Buffers reduce the tendency of pH todrift (becoming more acidic or alkaline)due to the introduction of contaminantssuch as paper coatings, inks, wash-upsolutions, and any other contaminantyou can think of.




! When purchasing fountain solution:"Is it a buffered or non-buffered solution?

"Is it compatible with your water source?

"Does the fountain solution provide the correctpH level and compatibility specified by theink and plate manufacturers?

"Do Not use a variety of different solutions!Find one that works for your type of printing.


What is conductivity?What is conductivity?




! Conductivity is the ability to transmit orconduct an electrical charge.

! The degree of conductivity is determinedby the number of ions present as a result ofminerals or other compounds in the water.

! The higher the concentration of ions, thehigher the degree of conductivity (andusually the harder the water).



! Water normally has a very low ion leveland registers very low in conductivity.

! Alcohol does not conduct an electriccharge and has a conductivity reading of 0,as does glycerin.

! Therefore alcohol and glycerin act to dilute,reducing the solution�s conductivityreading.



Why the need for conductivity?Why the need for conductivity?

! With the new technology that has evolvedin the printing industry, including bufferedand neutral fountain solutions, pH is notenough in determining the best level ofperformance of a fountain solution.

! Conductivity gives a more accurate wayto monitor the conductivity levelthroughout a press run.



! Whether the press operator adds 3 or 8ounces of solution to a gallon of water,the pH will remain the same, but theover-all chemistry is not correct for thetype of press that you are trying to run!




! Conductivity readings let us know whereour starting solution should be, and if itbecomes contaminated and problems arisewe have a base number to refer back toregardless of the pH level.

Why theWhy theneed forneed forconductivity?conductivity?This chart shows aFountain Solutionbuffered at a pH of4.5


How do we measureHow do we measureconductivity?conductivity?



! The unit of measure for expressingelectrical resistance is the �ohm�,and the unit of measure for expressingconductivity, the opposite of resistance,is the�mho�.



How do we measureHow do we measureconductivity?conductivity?! Because of the difficulty of measuring

conductivity in terms of �mho� units,a fraction of a mho or a �micromho�is normally used.

! A micromho is equal to one millionthof a mho.



! Conductivity meters are accurate, easyto calibrate, and simple to use.

! To take a reading just place the electrodein the solution and stir a few seconds.

! Most conductivity meters are digital anda reading will appear in the viewer.



How do we measureHow do we measureconductivity?conductivity?! The level of a solution is measured with a

conductivity meter, which gives readingsin micromhos per centimeter.

! Conductivity should be checked before andafter adding alcohol due to the fact thatalcohol dilutes the solution and will rendera false reading.


How do we measureHow do we measureconductivity?conductivity?! The rule of thumb for good

conductivity readings is about 900to 1000 mmhos over the conductivityof the water.

! The conductivity range encounteredby most printers will be under 3000micromhos (mmhos).




! The important fact to remember isthat there is no conductivity standard.You must determine the individualstandard for your press by conductingtests.

Fountain solution problems.Fountain solution problems.

What happenswhen too muchconcentrate is usedin the fountainsolution?



Too Much ConcentrateToo Much Concentrate

! If the recommended dilution ratio of thefountain concentrate is 2 ounces per gallon,this does not mean that 4 ounces per gallonis twice as good.

! Excessive use of fountain concentrate willcause problems and increase chemistry,material, and labor costs.



! When an overdose of a buffered fountainconcentrate occurs, the pH reading will notindicate this excess because the bufferingsalts limit the pH reading of the solution.

! A conductivity reading, on the other hand,will prove useful in determining excessconcentrate.




! Possible problems from too much concentrate."Ink emulsification (especially reds and blues).

"Background tinting.

"Poor ink-acceptance in image area, resulting inmottling or blinding of the plate.

"Premature plate wear from lack of ink lubrication.

"Slow drying of inks and possibly, of chalking.

"Stripping of the ink rollers.

Fountain solution problems.Fountain solution problems.

What happenswhen too littleconcentrate isused in thefountainsolution?



Too little ConcentrateToo little Concentrate

! Too little concentrate will cause many ofthe active ingredients found in the fountainsolution to be inadequate in strength to dothe job they are designed to do.

! Lack of adequate concentrate can bedetermined by both pH and conductivity.

! For best results, stay with a range of pHand conductivity that is most successfulunder your printing conditions.


Too little ConcentrateToo little Concentrate

! Possible problems from too littleconcentrate."Filling in of reverses and halftone screens."Scumming."Tinting."Inadequate gum will leave plate non-image

areas unprotected."Lack of anti-corrosive ingredients will lead

to premature plate wear.


Safety FirstSafety First



! Use care while mixing to avoid dangeroussplashes.

! Measure out the required amount of waterfirst.

! Add concentrate to the water.! If other components are required, add them

to the water/concentrate mixture.! Stir or mix all components to achieve a

uniform blend.




! Check pH and conductivity to be surethey meet the manufacturer�srecommendation (or the pre-establishedstandards for your press).

! If alcohol is required, add it after thesolution has been mixed to the desiredconductivity range.


SummarySummary

! pH and Conductivity determinations arethe first logical troubleshooting stepswhen press related problems arise.

! Most problems attributed to fountainsolution are due to too much or too littlefountain concentrate and the source water.

! Maintenance and cleaning of dampeningsystems will also eliminate a lot ofdampening system problems.



Where to Get More InformationWhere to Get More Information

! The following companies have providedthe information used in this presentation:

" Varn Product Company (201) 337-3600" Kohl Madden (800) 367-4657" Kodak Polychrome Corp. (414) 784-3720" Van Son Ink (800) 645-4182" GATF http://www.gatf.org


Thank YouThank You

! If you ever need Help!EuGene L. Van RoyWestern Wisconsin

Technical College304 N. 6th St.LaCrosse, WI 54602(608) 789-6260 or (608)

526-6600E-mail:

[email protected]

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pH, Conductivity and Offset Printing - University of Houstonsites.tech.uh.edu/digitalmedia/materials/3252/Fountain_Solution.pdf · pH, Conductivity and Offset Printing 2 Pressroom