Buildup on inking rollers or plate

Possible Cause

• Too much alcohol in fount solution.

• Fount additive not fully compatible with alcohol.

• Incorrect addition of the fount additive to the recirculation tanks causing precipitation of the gum from the additive.

Remedy

• Reduce alcohol level.

• Change fount additive.

• Add in sequence water, fount additive, then alcohol mixing thoroughly after each addition.

Feedback on dampening rollers

Possible Cause

• pH too acid. the ink is not taking up enough water in the image area of the plate

• Fount solution too cold, leading to increased ink viscosity and reduction in the water uptake of the ink.

• pH too high, the ink emulsifies too much ( interfacial tension between water and ink too small).

Remedy

• Decrease fount additive level or change the additive. do not reduce the level below 2%) by volume

• Raise the temperature in the recirculation tank(s).

• Reduce the pH

Pilling on the blanket

Possible Cause

• Surface tension of the water too high.

• Ink over emulsifying due to high pH.

• Level of dissolved solids too high causing over emulsification.

• Temperature of fount too high

• Setting too fast because the ink is not sufficiently emulsified caused by

• low water temp

• low pH

Remedy

• Change fount additive or increase the alcohol level

• Reduce the pH

• Clean out recirculation tanks and make up a fresh fount solution

• Reduce the temperature of the fount

• Increase water temperature

Tinting on plate and blanket

Possible Cause

• pH too high

• Temperature too high

Remedy

• Reduce pH

• Reduce the temperature

Scumming on plate

Possible Cause

• Ink over emulsifying

• Ink over emulsifying due to high pH.

• Level of dissolved solids too high causing over emulsification.

• Temperature of fount too high

• Setting too fast because the ink is not sufficiently emulsified caused by

• Often a problem with integrated dampening systems

Remedy

• Increase alcohol level

• Clean dampening system

Ink does not dry

Possible Cause

• Ink over emulsifying does not set fast enough

            – pH too high

            – Temperature of fount too high

            – Level of alcohol insufficient

            – High level of dissolved solids in the fount solution

            – Surface tension of fount too high

Remedy

• Change fount additive or increase the alcohol level

• Reduce the pH

• Clean out recirculation tanks and make up a fresh fount solution

• Reduce the temperature of the fount

• Increase water temperature

• Increase alcohol level

• Clean dampening system

Flying / Misting

Possible Cause

• Two Extremes

• ink over emulsifies

• ink not sufficiently emulsified

Remedy

• Adjust pH

• Adjust Temperature

Picking

Possible Cause

• Ink not sufficiently emulsified. the tack remains too high for the substrate

• The fount solution is too cold consequently the tack is too high

Remedy

• Increase the pH

• Reduce the percentage of alcohol

• Increase the temperature of fountain solution

Powdering / Chalking

Possible Cause

• Setting too quick ink does not take up enough water because.

      – pH too acid

      – Temperature of the fount solution is too low

Remedy

• Increase fount pH

• Increase fount temperature

Ink is not rub proof after-drying. Will offset or scuff in some binding operations

Possible Cause

• Ink vehicle has been absorbed by paper leaving pigment in chalky condition on top of the sheet.

Remedy

• Use a stiffer ink or less absorbent paper of a faster drying agent

Paper blisters or particles of coating stick to blanket

Possible Cause

• Coating not suitable for offset

• Stock is weak

• Ink to stiff

• Too much back pressure

Remedy

• Soften ink slightly

• Reduce back pressure

• Change paper

Unwanted patterns appear in solid grounds

Possible Cause

• Poor layout of sheet

• Emulsified ink

• Too much water being run on plate

Remedy

• Change Layout

• Change Ink

• Use plate that requires less water

Ink does not dry flat some areas dull and other shiny (Mottling)

Possible Cause

• Paper not of same porosity all over sheet

• Uneven thickness of Ink film

Remedy

• Try another paper

• Check ink control

Tinting

Possible Cause

• Ink and water forming an emulsion

Remedy

• Run less water on plate

• Use a more water resistant ink

• Try a different paper