TECHNICAL INFO




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Conventional offset /letterpress varnishes
Conventional “paste” type varnishes have numerous advantages, including excellent protection against humidity, ease of use and excellent rub and chemical resistance.

Formulation:
The oleoresinous formulation of thesevarnishes is of the same chemical nature as conventional offset / letterpress inks. Their siccativity is adjusted to optimise the drying time. The principal characteristics of the varnish are obtained by the incorporation of various additives.
Use:
They are extremely easy to use and do not require any specific equipment. They are applied from the ink duct, with or without fount solution, either wet-on-wet or wet-on-dry over conventional offset / letterpress inks.

Characteristics:
Drying takes place through penetration and air polymerisation and therefore involves some delay before handling and cutting / folding operations can be carried out on the printed material. Application with fount solution allows gluing reserves to be made.
Their compatibility when applied over conventional inks is optimal.
Incidents
 
  1. Hold out / not smooth

  2. Set off

  3. Gluing problems on varnished prints

  4. Poor drying
     
Probable causes and remedies
 
 1. Hold out / not smooth (back to incidents)
 
Cause
Too much anti set-off powder (if wet-on-dry varnishing).
Remedie
Reduce the amount of anti set-off powder.
Check the particle size.
 
 
Cause
Too much varnish.
Remedie
Reduce the amount applied.
Cause
Poor setting.
Remedie
Check the anti set-off powder.
 
3. Gluing problems on varnished prints (back to incidents)
 
Cause
Glue/ varnish incompatible.
Remedie
Use reserves, work with fount solution.
Use an acrylic varnish.
 
4. Poor drying (back to incidents)
 
Remedie
Add Colourless Drying Agent (1% max.). Too much drying agent
causes yellowing and has a negative effect on drying.
 
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