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Essential Rules In UV / Spot Varnishing In The Industry
In order to assist you in obtaining the best results when UV varnishing your jobs, we have formulated the following guidelines:
1. Only coated paper and board can be UV varnished.
2. Use only wax free inks when printing a job that is to be UV varnished or laminated.
3. Use inks free of fanal pigments or colour fading may result. We do not accept responsibility should this occur, as it is sometimes only evident days after the varnish has been applied.
4. Use minimal or no spray powder. If the job cannot be printed without spray powder, then use 2V Russell Webb (in the smallest possible quantity) from Graphica (Pty) Ltd.
5. A few imported papers do not UV varnish properly, due to various coating processes used in the manufacture of paper.
• If an unknown paper is used, or if you have doubt as to the UV varnish results, samples can be tested free of charge, before printing.
• Alternatively, if the job is printed on absorbent paper, it can at times be saved, by coating twice through our machines, thus laying down a ±12gms of varnish per sq meter, this is twice as expensive.
6. Storage of jobs varnished on both sides.
When a job is varnished on both sides, the surface tension on the sheet is greatly increased – similar to glass and plastic, which both have very smooth surfaces. After a few days, moisture from the air bonds the two UV surfaces together. When they are physically separated, varnish on one of the surfaces is sometimes pulled off. A similar effect can be experienced when separating plastic or glass. It is therefore advisable to inter-leave with a porous sheet of newsprint or similar.
The following precautions must be taken when storing UV coated material.
• A suitable cooling time of about two hours is needed for jobs before they can be stacked or transported. Urgent jobs collected before curing time is complete, (2 hours) stand the risk of plucking (the varnish is pulled off in spots). We accept no responsibility for jobs that have been damaged due to them being collected before they have had sufficient time to cure.
• No weight should be applied to the sheets eg: small stacks. It is preferable to stack the job vertically.
• Dry and cool conditions are necessary to reduce possibility of two-sided jobs sweating and sticking together.
• Interleaving is essential.
7. We cannot be held responsible for UV coatings where unrecommended inks with excessive wax are used and the UV varnish lifts.
8. We indemnify ourselves completely from claims made against ourselves where blister coating is concerned, as problems relating to this method of packaging are experienced internationally due to the fact that there is no perfect board/ink/blister coating combination. Also, we are not in a position to control heat, pressure and time which are major factors when applying the blister to board.
9. Spot Varnish
Due to paper and screen stretch the spot image can vary ±.5mm.
• Allow 15 to 20mm grip
• Supply Silkscreen positives (emulsion up) making sure they fit properly
• When possible please do not supply patched positives as this can effect register