Set-off on one part of asheet and arough finish on other parts, is almost certainly due to uneven spraying. will also cause an uneven stack.) Check regularly that applicator nozzles are spraying properly. To test this, hold a black sheet underneath the nozzle, allow it to spray two or three times and then examine the spray on the sheet.

It is always tempting to over·spray in an effort to 'insure' against but this will cause many problems later. If the ideal dosage results in then it would be better to increase the particle size rather than the amount of powder. If the grains are distributed widely enough on the sheet, they should not cause arough feel.

Using the incorrect powder can result in pinholing after varnishing or lifting of the laminate from the sheet. If these operations are subsequently to be carried out, use a powder which is compatible and will 'wet-out' in oil based substances, ie a

hydrophobic powder, or one which can be removed from the sheet entirely such as a vanishing/soluble type.

If using conventional inks prior to ultraviolet varnishing, a conventional powder can cause loss of gloss. Instead, use a soluble powder and pass the work through the press with the damping system engaged to clean the sheets.

Never use a soluble spray powder with an infra-red drying unit because this will result in a build-up of a brown sticky material - the powder melts at low temperature - which also sticks to the drier and can eventually damage it. With this type of system use a hydrophobic powder.

MAINTENANCE

If you have a problem with your spray powder equipment and you still have not found the answer having read this far, it is best to call a qualified engineer. If you operate the equipment on a single shift it is wise to have it serviced once ayear; if on adouble shift then twice ayear. Always keep equipment clean and dry, have it fitted only by aqualified engineer and buy the best system you can afford.