Indigos tend to be challenging to use with SLEEKpro technology when compared to dry toner. But with the right setup and stock, they can be successfully used with amazing results. Here are some pointers you can try.
(If you're using a digital toner press and are having trouble with sleeking, check out this article for tips specific to your application.)
Printing
You'll need at least 4 hits of digital ink at a minimum. Up to 8 hits may be necessary to achieve a sufficient ink buildup. Each hit should be at 100%, so you'll need at least 400% ink coverage.
Yellow is the most aggressive when compared to the other colors, and sticks best to difficult stocks. So contrary to our suggestion for Xerox print engines, we recommend using 100% Y for Indigos.
Avoiding picking
The key to this is to ensure the foil doesn't pull away from the digital ink until it gets to the stripper bar.
- Make sure the pull rollers are turned off
- Use bearer bars. Printing a 1/2" wide border around the whole sheet helps the foil adhere to the digital ink. (More on that here.)
- Use minimal take-up tension - just enough to keep the foil separating from the sheet at the stripper bar.
Curing time
Unlike dry toner, HP Ink needs time to cure before sleeking. Without this, we see picking (where the foil separates from the toner/digital ink before it has time to bond properly), or the digital ink coming clean off the sheet with your foil because the bond of the foil to the ink is stronger than the bond of the ink to the paper. To avoid this, we recommend waiting 8 hours before sleeking. We've seen okay results with waiting for as little as 2 hours, but anything below that doesn't give satisfactory results. And if you have any further processing to do after sleeking, wait at least 16 hours before doing it.
We understand that no digital printer wants to hear this. But from our experience, getting HP digital ink to completely cure before we put it through the foiling process produces the best results.
HP Blankets
Overprinting on top of foil can reduce blanket lifespan. To mitigate this, we recommend running 10 sheets, then a blank cleaner sheet, followed by 10 more.
Ink Maintenance
The inks need to be rebuilt periodically or they won't adhere to the paper or to each other. We suggest doing one color a week so that each is rebuilt once a month.
Further information on how sleeking works and some additional tips and tricks are available on our website and YouTube channel. A great starting point would be this video from our Print2Finish event: https://youtu.be/t52S-wljJwY
We also have a series of blog articles covering various SLEEKpro topics including:
- Digital toner presses & the SLEEKpro process
- Finding the best temperature and pressure for sleeking
- How to avoid picking on fine detail
If you're still struggling to make sleeking work for you after trying the tips above, we're also happy to help. Reach out to us at service@skandacor.com to schedule a virtual or in-person call.