FOUNTAIN SOLUTION Fundamentals of Offset Dampening

1 FOUNTAI N SOLUTI ONFOUNTAI N SOLUTI ONFundamentals of Offset DampeningFundamentals of Offset DampeningSheetfed OffsetWe b Of f s e tSheetfed OffsetWeb OffsetPrinting auxiliariesPrinting auxiliariesReferencesWe would like to thank all companies and institutes for their friendly support with information material and picturesFigure 1 POLYCHROMEO sterodeFigure 3Dr. Herbert BendlinUSF Deutschland GmbHProzess- und AbwasseraufbereitungssystemeFigure 4Dr. Herbert BendlinUSF Deutschland GmbHProzess- und AbwasseraufbereitungssystemeFigure 5 DRAABE GmbHHamburgFigure 12Kr ss GmbHHamburgFigure 13 Bundesverband Druck "Reduzierung des Alkoholgehaltesim Feuchtmittel"Art. Nr. 86438, 19933 PageFrom Tap Water to FOUNTAIN SolutionWhat kind of water quality is required for Offset printing?

2 4 Methods of Water TreatmentWater softening ..4 Complete demineralization ..5 Reverse osmosis ..5 Treatment of deimineralized water ..5pH value and ConductivityWhere does the term "pH value" come from? ..6 Importance for Offset printing ..6 Stabilization of pH value ..6 Measurement of pH value ..6 What is "conductivity"? ..7 Conductivity and quantity of FOUNTAIN SOLUTION additive ..7 Requirements and Tasks in Offset PrintingProtection of printing plate ..8 Antimicrobial effect ..8 Setting of surface tension ..8 Alcohol reduction in Offset printing ..9 Exact determination of alcohol between alkaline papers and acid FOUNTAIN solutions ..10 Increase of pH value in FOUNTAIN SOLUTION ..10 Piling on the blanket ..10 Stripping of ink rollers.

3 11 Running blind of printing plates ..11 Corrosion in printing presses ..11 Modern FOUNTAIN SOLUTION FOUNTAIN SOLUTION service ..12 Problems, Causes, 13/14 Table of Contents4 From Tap Water to FOUNTAIN SolutionDuring the last 30 years Offset printingdeveloped into the most importantprinting process. The key for thissuccess is and always has been thehigh productivity and quality as well asthe relatively easy production of theprinting typographic, gravure printingand screen printing base on physicalprinciples, Senefelder already definedhis printing procedure - lithography(the precursor of Offset printing) - as"chemical printing process". Printingand non-printing areas are notseparated by differences in height, butby varying wetting behaviours of theprinting forme towards water and non-printing areas are hydrophilic,the printing areas are 1 shows the typical structure ofan Offset printing 1: Structure of Offset printing plate,screen dot on non-printing aluminium oxideFollowing this principle, the printingprocess does not only require ink, butalso water.

4 This water must showcertain properties, which are reachedby water treatment and specialfountain SOLUTION additives, kind of water quality isrequired for Offset printing?Depending on its origin, water canfeature very different qualities andcomponents. The assessment of awater quality with "good" or "bad" canpossibly vary very much, because it isinfluenced not only by its components,but also by the intended drinking water should be free ofodour and taste, low in germs andrelatively low in its natrium chloridecontent,.. cooling water should be free ofcorrosive washing water should be soft withrespect to the needed what are the properties required ofwater used in the preparation offountain SOLUTION ?

5 Mostly drinkingwater is used, only few companieshave their own FOUNTAIN . Theregulation for drinking water leaves alarge scope, which means that waterqualities can be very the typical components, thecomponents relevant for printing aremarked with *:Salts/cations: Natrium, potassium,calcium*, magnesium* and traces ofiron, manganese, zinc and aluminiumSalts/anions: Hydrogencarbonate*,chloride*, sulphate*, nitrate*, phos-phate and silicateGases: Oxygen, nitrogen, carbondioxide and organic combinations andmicroorganisms (drinking water < 100germs/ml).The influence of these components onthe printing process as well as therecommended limits can be seen infigure 2.

6 If the water quality signi-ficantly differs from these nominalvalues, a water treatment is softeningDuring this process the hardnesscausing components calcium andmagnesium are replaced by indifferentions (natrium) via a cation principle is shown in figure 3. Thesalt content remains unchanged or isslightly increased. Corrosive anionsand the undesired portion ofhydrogencarbonate in highconcentrations are not variations in the water qualityremain. According to theserestrictions, the softening is onlyconditionally suitable for thepreparation of FOUNTAIN SOLUTION . Ionexchangers have to be regeneratedwith a natrium chloride SOLUTION after acertain period of operation.

7 Theretained calcium and magnesium isFig. 3: Principle of water softeningIngredientsInfluence/ProblemRec . formerCalciumMagnesiumStripping, pH value,running blind of plateca. 8 -12 dHHydrogen carbonatepH value100-200 mg/lChloridecorrosion25 ppmNitratecorrosion20 ppmSulphatecorrosion50 ppmFig. 2: Typical components of tap water and theirlimits for Offset printingTap water (drinking water)Softened waterNatrium ionCalcium ionMagnesium ion5again replaced by natrium and theprocess can start again. Residues ofnatrium chloride have to be removed(washed out) before the system canbe used demineralizationThe complete demineralization workson the principle of a ion this process all ions (cationsand anions) are replaced by thecomponents of the water, hydrogenions and hydroxyl ions become result is completelydemineralized water, which isused in car 4 shows the principle ofcomplete demineralization.

8 Completelydemineralized water is not suitable foroffset print (see also "Treatment ofdemineralized water").The ion exchangers of the completedemineralization must be regene-rated with acid and lye. The wastewater has to be neutralized before it isintroduced into the sewage osmosisThe reverse osmosis is comparablewith a filtration, in this case the "filter"is a membrane. This membrane isonly permeable for the small watermolecules, but not for salts,microorganisms and othercomponents. If water is directed underpressure past a membrane, thestream divides into two part streams: an almost saltfree water quality,which comes through the membraneand the very salty waste water, which isdirected past the hard water qualities have to besoftened prior to the osmosis.

9 RO-water also has to be treated for thepreparation of FOUNTAIN SOLUTION (seefigure 5).Treatment of demineralizedwaterPractical experiences show that waterwithout hardness causing componentsis not very suitable for Offset particularly applies, if norehardening is done by the paper (seealso "interactions ofalkaline papers with acid fountainsolutions"). Hardness causingcomponents have a positive effect onthe ink/water balance. Thereforehardness causing components have tobe added to soft or treated water. Thehardness should be in the range of 8-12 dH (dH - German hardness).In this context two possibilities have tobe discussed:1.

10 Mixture with tap water:This inexpensive SOLUTION can beused whenever the water quality isconstant and no disturbing salts, corrosive chlorides, Rehardening with AQUATREAT:A special additive, which in additionto natural hardness causingcomponents also suitable water quality is one of thepreconditions to guarantee anunproblematic printing process. Inaddition it is absolutely necessary thatthe FOUNTAIN SOLUTION additive has beenadjusted to the application. Nowadaysmodern FOUNTAIN SOLUTION additivescomply with a variety of requirements. Stabilization of pH value in afavourable range for printing Protection against corrosion ofprinting plateMethods of Water TreatmentComplete demineralizationDemineralized Watercation resinanion resinnatrium ioncalcium ionmagnesium ionchloridehydrogen ionhydroxyl ionsulphate ionhydrogencarbonate ionwater moleculeFig.