Hey guys,
So when you said PolyPropylene bags, I immediately thought of Poly-Mailer bags... I actually started printing these recently, and have some good advice for them if anyone is interested.
http://www.sonic-weapon.com/portfolio-category/poly-mailers/I print with Nazdar PA Series (PolyAll) and use a 305 mesh (230 puts down too much and you can feel the hand, like if you used thinned out acrylic, just feels heavy, the 305 feels seamless and has still maintains great opacity, even over blacks)
I use standard screen opener to keep everything clean after using these inks, as the inks tend to air dry after 15-20 minutes printed, or about 45 minutes or so in the screen. To keep the ink from drying in the screen for a large run, I use the Nazdar suggestion of adding enough ink to print for about 30-40 minutes, every 45 minutes I add a little more ink and keep printing. Always have to backflood each print, but the great thing about the PA series of ink, is that it doesnt require a catalyst (another thing I didn't want to have to deal with)
You can get these inks from McLogan supply, or Nazdar SourceOne directly, and SourceOne can also PMS match, they will even ask what color plastic you are printing over to make sure PMS matching is accurate over that color (you can also send them a sample of the substrate you're printing)
Anyways, after I am finished printing, I discard any ink in screen (as it could have mixed w/ earlier ink added and may have begun drying, you don't want to contaminate the fresh inks)
TO keep everything clean, I fill clear condiment or ketchup bottles with the PA series ink and add to screen as needed. A quart of PA series ink runs about $45 but I'd say you can get about 500-1000 prints out of a can on the 305 or higher mesh, probably more than 1000, I still am working on reducing my waste (why I switched over to the squirt condiment bottle vs filling small dixie cups ahead of time and taping them up before adding a little more when needed)
Anyways, hope this is helpful. Once printed on my vacuum table, same as I'd use for flatstock, they're air-dry to the touch, although super smelly, you need good ventilation (I work and print in my garage with 2 fans exhausting and wear a respirator the entire process)
Clean up everything with Screen Opener only, mineral spirits is no match for this ink, only screen opener, or press wash...