Silicone Screen Printing Ink

Part of what makes the screen printing industry interesting is all of the innovations and new products you see year after year, however the actual printing inks don’t really change all that much.  You have some higher quality inks that are softer and more opaque that replace what you had previously used. And of course there are some special effect inks that have really unique properties and look really cool, but none of those are all that new or really useful in high volume production.  With the popularity and availability of technical shirts, screen printers are faced with specific challenges when decorating these garments, the most frustrating and costly being dye migration.  There are some newer inks that help combat dye migration, including Wilflexs’ line of Top Score inks, which do a decent job when used correctly.  These tend to be less effective with certain colors and fabrics that have been colored by sublimation.  In these circumstances a bleed blocker grey underbase is the only real way to block the dye, but anyone who has worked with it knows it it’s only a little bit easier to print with than concrete.  It’s so thick and patchy as an underbase and when you add on the top colors you end up with such a heavy application it really ruins what was once a nice, breathable tech shirt.

Recently I came across some tech shirts that had a very soft, stretchy, lightweight print on them.  I asked my ink rep what kind of ink it was and it turned out to be silicone.  There aren’t many ink manufacturers making the stuff and he couldn’t event get a sample for me.  After some web searching I found 2 reputable sources, Nazdar and Rutland.  The ink comes in 2 forms, ready-for-use colors and a base with pigment concentrates; I ordered a few colors from Nazdar and spoke to a CS rep on the phone and she sent me over some tech info.  The unique thing about printing with silicone is that is has to be activated by adding a catalyst (3-5% by weight), this gives it a pot life between 1-24 hours depending on how you store it after use.  I have found using 3% will give you a good amount of screen time and you can store the remainder in a sealed quart cup and it will keep for a day without hardening.  The ink will partially cure in the dryer and fully cure after it has fully “cross-linked”, which is what the catalyzer does.

The ink is very light and creamy and does print similar to plastisol ink.  The cured ink is almost rubbery but it’s very light and super stretchy.  Best opacity is achieved using the lowest screen mesh possible for the design, low squeegee pressure and a strong angle.  A thicker screen coating will get more ink through, so you can layer up the emulsion or use capillary films to build thickness.  I have found a normal-thick coating on a 110 mesh is good for most applications.  The ready-for-use white is very opaque and a print-flash-print is good enough to get full opacity.  The other colors do require a thick screen coating and low pressure if you don’t want to use an underbase.  Printing fluorescent ink always require a white underbase and should be mixed with the clear base instead of the regular opaque base.  I have found the strong flouro colors are very transparent and don’t pop like plastisol flouros do.  The flouro blue I tried was so light that I had to call Nazdar to ask if I was doing something wrong.  Turns out I wasnt and their answer was “that’s just the way it looks”.  See below.

The biggest benefit to using this ink is it’s dye blocking abilities.  We print on customer supplied Nike shirts that have sublimated graphics on them and have never been able to fully control dye migration until we started using silicone.  The cured ink is porous so the dye gasses that would normally stick in your ink simply flow right through.  You see a little bit of dye migration at the back end of the oven and over time it actually goes away.

migration

I have put together a tip-sheet for to help with the learning curve.

  • Pre-heat your pallets!
  • Keep an eye on your flash timer and keep it as low as possible, it will be a long flash at first.
  • Oven temp is similar to plastisol in my experience.  Cured inks will feel slippery and not tacky.
  • Watch for partially cured ink during your print run, little balls can form and block your stencil.
  • Never mix with plastisol, make sure your squeegees are completely clean
  • You must have clean pallets, you will see your dirty pallets in your ink, especially strings and bumps.
  • low squeegee pressure and a strong angle for good opacity
  • 3-5% weight of catalyzer
  • Max 20% pigment concentrate to base.
  • Only catalyze what you plan to use, unused ink has to be thrown away and it’s not cheap.
  • You cannot print wet-on-wet.

That’s it, easy.  If you do a lot of tech shirts, especially sublimated this ink is invaluable. We charge an addl 20% (or so) for it and our customers love it.

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