Category Archives: Gravure

Volcanoes

Web heat is excessive

Decrease web temperatures. Excess heat vaporizes some fast drying solvents resulting in eruptions through the surface

Solvent selection is poor

Change solvent blend. Fast solvents may erupt through the surface before the ink is dry

Cylinder is too deep

Reduce the depth of the cylinder

Streaking

Foreign matter in the ink

Filter the ink

Dried ink skin is in the system

Filter the ink. Keep a lid on the ink container

Pattern changes with oscillation

Check for foreign substance under the blade Clean blade and filter the ink

Doctor blade is nicked

Lightly polish to remove burr. If streaks oscillate, change doctor blade

Static

Substrate is static prone

Use web tinsel or other antistatic devices

Substrate or print moisture is too low

Increase web humidity. Increase steam line or spray mist

Ink viscosity is too low

Add fresh ink or add pigmented extender to increase viscosity

Snowflaking

Stock is too rough

Use electrostatic assist with (polar solvents)

Ink viscosity is too high

Reduce ink viscosity

Ink is drying too fast

Add slower drying solvents to the ink or adjust print speed to ink drying rate

Substrate is too cold

Check substrate for proper smoothness or moisture content and temperature

Impression is too light

Increase impression. Verify correct roller durometer. Ensure uniform pressure across web

Screening

Ink viscosity is too high

Reduce ink viscosity

Ink is drying too fast

Add small amounts of slower drying solvents or speed up the press

Ink is starving

Maintain correct amount of ink in the sump

Blade angle is too sharp

Flatten wipe of the blade

Impression is lacking

Check impression setting and durometer of the impression roll

Ink temperature is too high causing the cylinder to heat up and the solvenls to evaporate

Cool inks or use slower solvent

Railroads

Doctor blade is scratched or nicked

If streaks oscillate, change doctor blade

Cylinder surface is nicked

Lightly polish or replace cylinder

Pattern changes with oscillation

Check for foreign substance under the blade. Clean blade and filter the ink

Cylinder has chrome deposits or high spots

Lightly polish cylinder to remove burr

Pinholing

Ink is failing to form a continuous film

Adjust ink to reduce viscosity. Use a more active (wetter) solvent

Stock is too rough

Use electro-assist (with polar solvents)

There are imperfections in the stock

Adjust doctor blade to carry more ink. Use coating primer if possible

The ink is wrong for the substrate

Reformulate or replace ink

Film treatment is poor

Retreat or replace film

Worn cylinder, insufficient film transfer to cover substrate

Re-make cylinder

Picking

Ink is drying too slowly

Add faster drying solvent

Oven temperature is not high enough

Increase heat and air velocity

Ink viscosity is too high

Reduce ink viscosity with thinned extender varnish or solvent

Idler rolls are dirty or tacky

Clean idler rolls and/or wrap with a non stick material such as Teflon

Web is rewound too warm

Reduce chill roll temperature

Re-work is “worn out”, resin balance is poor

Re-make ink or refresh in sump

Mottle

Ink viscosity is too low

Increase ink viscosity

Ink viscosity is too high

Reduce ink viscosity

Paper stock is too dry

Introduce moist air

Ink is not wetting stock properly

Change blade angle, then change solvent selection

Ink or substrate is too cold

Vary temperature of ink and substrate. Allow to warm to room temperature

Pigment selection is poor

Reformulate ink

Cylinder is too deep

Re-etch or replace cylinder

Print impression is excessive

Reset for lighter impression

Press returned ink is unusable

Increase resin solids. Use fresh ink

Press speed is too low

Increase press speed

Ink might be printing characteristics of substrate

Check alternate substrate for smoother surface

Make sure solvent blend is correct for resin balance

Check solvents (blends) for accuracy – run GC

Hazing

Doctor blade wipe is improper

Check and reset doctor blade setting

Cylinder is slightly rough

Polish cylinder

Ink is over-pigmented

Add clear extender

Chrome is poor on cylinder

Remake cylinder

Humidity is too high

Add a slower drying solvent to the ink

Solvent combination is poor

Change the solvent combination

Web tension is improper

Check and adjust web tension