Ink drying in sheet-fed

• Physical part (ink absorption, ink setting )

• Goal is to have enough setting that ink would not set-off in the

delivery pile

• Chemical Part (oxidation)

• Oxidation of ink binder

• Oxidative drying lasts for several hours depending on the type

of ink and properties of the substrates

• Drying agents (siccatives) will accelerate the drying process.

Spray powder

• Spray is used to avoid ink set-off

• Spray powder is the distance holder between the sheets.

• It increases the amount of oxygen to improve the oxidative drying process.

• Spray

• 10 to 80 microns

• calcium carbonate

• organic, vegetable based powder of natural

starch

Drying problems - sheet-fed

• Inadequate drying

• Similar smearing as in heatset if ink layer not dry enough

• Silk grades

• same problems but sheet-fed inks a bit better than heatset inks

• Blistering, fibre roughening, waviness

• does not occur

• Cracking

• also problem in sheet-fed

• not due to drying but use of heavier grades