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SOLVENT BASED SCRATCH
OFF COATINGS
When using solvent-based scratch off coatings it is imperative
that the pads used be resistant to the solvents. Buna-N rubber is
commonly used, as are some grades of polyurethane rubber. WHEN
COATING ON MOST GRADES OF CLAY COATED PAPERS, A PRIOR APPLICATION
OF A RELEASE COATING IS NOT NECESSARY.
USAGE
The clay-coated papers should be tested with coating prior to
running. Having the ability to pre-apply and dry {or cure} a
release varnish prior to the scratch-off coating application
achieves the following advantages:
- Wider choice of colors
- Superior hiding
- Easier removability
- Cleaner appearance
In order to maximize hiding, print
the "message" in as light a screen as possible. In addition,
preferably print in colors other than black.
To maintain proper viscosity , keep
the coating cool and circulate {using an air pump] from the
application pan to the pail. The viscosity must be monitored
routinely {using a #4 or #5 zahn cup}. The proper dilutent must be
added as required to maintain the optimum printing viscosity.
Avoid uneven application of coating
{usually caused by pads swollen by solvent or from excessive
pressure being applied when printing}. The high ridges produced
take longer to dry. This can cause offsetting, particularly when
the structure is guillotined.
Keep application rollers clean .
Check metering equipment to assure a unified lay down. A smooth
application is critical. If necessary, filter the coating being
returned to the pail. Keep the coating cool during printing.
STORAGE
Store at room temperature. Avoid freezing in excessively low or
high temperatures, as it will affect viscosity. Do not contaminate
unused coating with foamy or dust-laden product.
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