Fountain solutionConductivitypHdH

fredag 16 maj 14

PPD

Water and water treatment! Certain ions that are typically present in

water can react with paper coatings or ink pigments.

! Understanding the composition of the water source feeding the plant can explain some press problems or point to an appropriate treatment method.

fredag 16 maj 14

PPD

Water and water treatment! Interactions between ink, fountain solution and

paper can be influenced by the presence of calcium ions.

! The presence of calcium in magenta ink is well known, and can cause deposits on magenta ink rollers and blankets.

! Accumulation of calcium from paper coatings or from fountain solution can lead to scaling problems.

fredag 16 maj 14

PPD

Water and water treatment

! Calcium! iron! Magnesium! oxygen! Sodium! carbon dioxide! hydrogen carbonate

! hydrogen (ion)! chloride! bacteria!! Sulphate! Algae! nitrate! floating substances

Elements and components in influent (tap)water

fredag 16 maj 14

PPD

Fountain solutions! Since successful ink transfer requires

compatible chemistry,matching ink and fountain solutions is critical.

! The fountain solutions must keep the printing plate clean while allowing the ink to transfer efficiently.

! These properties can be provided by use of a fountain solution concentrate.

fredag 16 maj 14

PPD

Fountain solutions! Fountain solution components are very

proprietary and often customized to a specific plant.

! Measurements help determine their effectiveness both before and during printing.

fredag 16 maj 14

PPD

Fountain solutionsComposition of fountain solution concentrates! Buffer systems to adjust pH value! Film forming hydrophilic and wetting substances! Biocides, fungicides, for anti-microbial equipment! Complexion agents to bind scaling components! Anti-piling agents! Co-solvents to keep the system homogeneous! Anti-foam agents! Corrosion inhibitors! Release agents (alcohol free and alcohol reduced)

fredag 16 maj 14

PPD

Water and water treatment! Depending on the concentration of

calcium and magnesium salts, water is classified from hard to soft.

! Hardness is expressed in degrees.! One degree German hardness (1dH) is

equal to 10 mg of calcium oxide per litre water.

fredag 16 maj 14

PPD

Water and water treatment! Water and water hardness

! Water (H2O) consists of hydrogen and oxygen, but as tap water it reaches the printer in different qualities and different degrees of purity, depending on its origin (groundwater or other).

! Even in clean rainwater dirt particles are present.

fredag 16 maj 14

PPD

Water and water treatmentFountain solution! dH-value (hardness = dH german hardness)! Describes the amount of calcium oxide! ! Very soft water! ! 0-4 dH! ! Soft water! ! ! 4-8 dH! ! Medium soft water! ! 8-12 dH! ! Medium hard water! ! 12-18 dH! ! Hard water! ! ! 18-30 dH

! !fredag 16 maj 14

PPD

Water and water treatmentFountain solutionTo hard can give: (over 15 dH ):! Hard ink rollers! Building of ink on ink rollers and blanket! Uneven transfer of the fountain solution! Unclearness in the screening tonal value! Mirror printing

! !

fredag 16 maj 14

PPD

Water and water treatmentFountain solutionTo soft can give:(under 7 dH ):! Uncleaness in non printing areas giving:! Increscent of the water on plate:! Giving to much emulsification:! Prospounds of the drying time of the ink

! !

fredag 16 maj 14

PPD

Fountain solutions! pH

! pH is the unit of measurement for acidity or alkalinity.! The letters pH stand for pondus hydrogenii (potential

hydrogen).! A neutral solution such as pure water has a pH value

of 7.! Solutions with a lower pH are called acidic, and

solutions with a higher pH are called alkaline. ! The pH scale ranges from 0 to 14.

fredag 16 maj 14

PPD

Fountain solutionspH

acidic alcaline

fredag 16 maj 14

PPD

Fountain solutionspH

! Should be slightly acid, it keeps the non-printing areas cleaner and slightly neutralized

! Measured with idicator paper or electric pH-device! pH between 4,8 - 5,3 usually works best! (On sheet printing kan sometimes little higher 5-6)! (In web print often about 4,5-5,0)

Important !A change pH one step is 10 times changeEx. change of pH 5 to pH 4 is 10 times more acidAnd a change of pH 5 to pH 3 is 100 times more

acid

fredag 16 maj 14

PPD

Fountain solutions! Conductivity

! This is measurement of the ability of a fountain solution to conduct electricity

! Checking fountain solution conductivity is particularly important when running a buffered fountain solution which tends to hold a constant pH reading despite great changes in the water quality.

fredag 16 maj 14

PPD

Fountain solutionspH -to much alcaline water gives:

! The water friendly areas on the plate will be destroyed

! Tinting or toning! The ink wants to emulsification to much! Greater danger to contamination to other inks! The plate gets grayish

fredag 16 maj 14

PPD

Fountain solutionspH -to much acidic water gives:

! Toning or tinting on non-printing areas! Blind plates! Grayish solid areas! Shorter life term of the plates! Decreased drying capability with the inks

fredag 16 maj 14

PPD

Fountain solutions

The amount of emulsificated water increase if:! pH-value increase! The hardness of the water decrease! The amount of IPA decrease! The viscosity of the ink decrease! The temperature increase

fredag 16 maj 14

PPD

Fountain solutionsTo small amount of fountain solution affects:

! Bad preparation of the plate, toning or tinting! To little buffering, variation in the pH! To little reduction of the surface tension, water

spots on the plate! Increased water in ink - unwanted emulsification

fredag 16 maj 14

PPD

Fountain solutionsTo high amount of fountain solution affects:

! Thinner ink, instable ink/water balance, emulsification

! Build up on ink rollers! Increasing dot gain! Blindness of the plate or gray areas! Attacks on non-printing areas, unstable wetting

of the plate, toning or tinting! The drying of the ink will be longer

fredag 16 maj 14

PPD

Fountain solutions! Check your conductivity and pH value

regally, both when the fountain solution is new and after a couple of days production

! A correct emulsification and a print result in control demands a stabile fountain solution

fredag 16 maj 14