A challenge that our clients commonly come across when they're doing sleeking (applying digital foil over toner) is 'picking'.
Picking happens when the foil separates from the toner before it has the chance to bond properly. It's especially common on fine detail, for example, scripted font, detailed text, etc.
It can look like the toner is completely removed, leaving nothing behind, or the area will be a dull black as if the top layer of print has been pulled away. This is especially applicable to HP Indigo prints when using multiple hits, and the primary causes are the foil separating from the sheet before the stripper bar, or excessive heat or pressure.
The key to avoiding this is to ensure the foil doesn't pull away from the ink/toner until it gets to the stripper bar, and here are a few tips on doing that:
Make sure the pull rollers are turned off
Use bearer bars: More on that in this video on our channel, but bearer bars provide a good, wide surface for the foil to bond to, keeping it taut so it doesn't separate from the sheet before it gets to the release bar at the back of your sleeking device.
Use minimal take-up tension - just enough to keep the foil separating from the sheet at the stripper bar without pulling it off the sheet while it goes through the machine
Reduce your heat and pressure in small increments.
If you're still having trouble after trying these tips, let us know. You can email us at firstname.lastname@example.org or schedule a virtual or in-person call.