Print defects in heatset

Paper related

• print through• optical mottling

Paper surface related

• backtrap mottling, water mottling• scuffing (rub-off)• picking, hickeys

Drying related

• smearing, blistering• fluting, cockling• fibre roughening, cracking

Accumulation related

• carry-over piling, dusting• ghosting, vanishing dots

Scuffing with matt/silk grades

Printed signature goes through many operations that involve pressure and movement at the same time

Too low drying

• Inadequate drying

Too high drying

• Blistering• Fibre roughening• Cracking• Fluting

Drying problems

Runnability

Good runnability is usually connected to accumulations on blanket vs. washing interval

There is always something accumulating on blankets

• washing interval can be from 20 000 copies up to hundreds of thousands copies

Accumulation can be said to affect runnability if

• washing interval is reduced significantly• print quality detoriates• risk of blanket damage

Accumulation problems

Coating picking (Hickeys)

• usually not surface strength problem but connected to papermaking process

Carry-over piling

• printing ink printed in previous unit gets tackier in following units and starts to pick coating surface

Dusting / Linting

• accumulation of pigment / fibre particles on non-image area of the blanket

Ghosting / Vanishing dots

• the most current problem in heatset printing!• main mechanism still unsolved• a lot of studies in recent years

Coating picking

Carry-overpiling

Dusting

Hickeys

Vanishing dots and ghosting

ghosting vanishing dots