SJH scratch-off ink coverage test: strong coverage with clean scratch-off — for lottery, promotional and security cards.
Scratch-off ink is the core material for instant lottery, promotional and security cards. Common faults: too hard to scratch, bleed-through, powdering and residue. Here are the causes and fixes.
1. Too Hard to Scratch
Over-thick covering layer, hard formula or over-drying. Fix: print 2-3 thin even coats, match formula hardness to the scratching tool, control drying temperature.
2. Bleed-through (Poor Coverage)
Underlying graphics visible before scratching. Fix: more printing passes, high-coverage ink (opaque, non-transparent from the back), even printing without voids.
3. Powdering / Peeling
Coating falls off during transport or before scratching. Fix: high-adhesion formula, proper substrate treatment, better abrasion resistance.
4. Residue After Scratching
Leftover ink marks. Fix: optimize film former ratio so the coating peels off cleanly in one scratch.
SJH Ink Advantages
Strong coverage, opaque, non-transparent from the back
Selection, detection, printing and ordering — answered.
The scratch layer is too hard to scratch — why?
Three common causes: the cover layer is printed too thick; the ink formula is too hard; or the drying temperature is too high and over-cures the coating. Check in this order: film thickness (screen printing should be two to three even thin passes), formula hardness against the scratching tool, then drying temperature.
The underlying print shows faintly before scratching — how is that fixed?
That is show-through from insufficient opacity, too thin a film or uneven printing. Increase the number of passes until the cover layer is fully opaque, raise the ink opacity, and ensure even printing with no misses.
The scratch layer powders off in transit — what to do?
Usually poor adhesion between ink and substrate, weak abrasion resistance, or inadequate substrate preparation. Use a scratch-off ink with strong adhesion, prepare the substrate properly (clean surface, suitable roughness), and raise the coating abrasion resistance.
Ink residue remains after scratching — how is it adjusted?
It relates to the film-former ratio and the elasticity of the coating. Reformulate so the coating lifts in one piece without residue, and rebalance elasticity against hardness.
How can these problems be avoided before a bulk run?
Through proofing. Request printed proofs and test opacity, scratch feel and adhesion on your own substrate and press before committing to the bulk order, which avoids reworking an entire batch.
