Not just for lottery tickets, scratch off ink can be used with any kind of retail promotional project where you want your customer to have the excitement of revealing a prize or discount amount. Scratch-off ink is a special rubberized ink coating that can be applied using screen printing techniques. This ink obscures a message underneath, and can be removed by scratching with a fingernail, coin or some other object.
How's it work? First the tickets are printed, usually lithographically or digitally, and left in 'press sheets'. Then a special release varnish is screen printed over the prize area. This varnish protects the message from overzealous scratching, and also gives a consistent surface for the scratch-off ink to adhere. Then the scratch-off ink is applied on top of that, and if necessary, an overprint coating for additional protection or as a design feature.
It sounds simple, however scratch-off projects are not without their pitfalls. Here are some tips to make sure your job is a winner:
1. Use coated stock.
Uncoated coverstocks can absorb quite a lot of varnish, and the toothy surface can provide such good adhesion to the scratch-off ink that it's impossible to remove. Stick with coated stocks, either gloss or matte for the best results.
2. Use minimal press powder, or depowder sheets.
Press powder can interfere with the varnish and scratch-off ink adhesion, as well as clogging screens. Try to use as little powder as possible. If it's necessary to use powder due to heavy coverage, consider depowdering the sheets after they are dry.
Likewise with digital printing: some digital printers deposit a 'fuser oil' on the sheets. This can make it impossible to print the varnish - it doesn't stick. If the tickets are being digitally printed, it's always advisable to test varnish application before running the entire job.
3. Screen back the prize message so that it won't be visible.
Scratch-off is not perfectly opaque. Try to make the prize message as low contrast as possible to prevent people from being able to spot winners through the coating. Best results are from using two different percentage tints of black only. Be extra careful with digital printers, as the toner or dry ink can pile up quite thick and allow your message to be viewed in relief, even after both coatings are applied. Testing is always a good idea.
4. Mark registration on the press sheet
If you are providing press sheets to have scratch-off applied to them, make sure you mark the top sheet on the stack with the grip and guide positions. Using consistent registration edges is crucial to make sure everything lines up properly.
5. Identify different versions on the layout
Keep in mind that once the scratch-off has been applied, all the tickets will all look the same. So if you have different versions (prize amounts, winners/try again, ect.) that need to be kept separate, it's a good idea to mark these outside the trim area on the layout or imposition.
6. Allow for drying time
Scratch-off ink is not a UV curing ink, so it will need time to dry before it can be handled. Make sure your project timeline includes this drying time, especially if additional bindery operations are required such as folding or perforating.
Follow these tips, and you won't be leaving your scratch-off job to chance! And remember, scratch-off ink is one of many different specialty inks that can be screen printed.
Check out some related blog articles: