Superimposing one colour onto another so that the first down does not lay properly before the next colour is printed.
Causes:
– Incomplete drying of the first colour down prior to printing the second down colour;
– Excessive plate to substrate pressure of first down colour;
– Dyes may cause some plasticisers o migrate;
– Second colour not printing due to:
- I Low viscosity;
- Ink drying too fast;
- Low or high pH;
- High holdout of substrate.
Solutions:
– Increase drying speed of ink, use faster evaporating solvents, balance dryers, reduce ink viscosity or reduce ink film with better metering. Decrease anilox volume and/or decrease dryer temperature;
– Reduce impression pressure of first down colour;
– Do not use dye-type inks with plasticised substrates;
– Second color solutions:
- Increase second down ink viscosity to higher than first down ink;
- Slow down drying by adding slower solvents, stopping air or heat blowing on plates and increase machine speed;
- Adjust pH to specifications;
- Change substrate, reduce ink film thickness or increase drying capacity.
