I am not one for analog printing processes or indeed digital ones, come to think of it I am not one for print processes at all. But making this split-flap display requires a good chunk of knowledge in this area, as the flaps need to be printed onto and the traditional process has been to use screen printing with oil-based inks.
I am very luck to be in a position where I can easily do screen printing with professional facilities, free of charge, however they don’t really allow the use of oil based inks, which are apparently a dying art, primarily because of genuine health and safety concerns in the fumes associated with them and their related cleaning, thinning and retarding chemicals. Oil based inks work best because they are hard wearing and permeate into plastic like polypropylene better.
Trip to the printers!
On Tuesday I went to use the above facilities to do some tests with the kind help of a colleague who runs the facilities called Liz Wilson. She mixed up a bunch of potion inks using her screen printing mojo, and our first ink was to the following recipe:
- 1/3rd Aqua Art Mix (white)
- 1 Tbsp. System 3 Textile (glue/binder ? not sure)
- 1 Tbsp. System 3 White Acrylic Ink
Liz’s special mix
This potion worked very poorly unfortunately, it was too think and so stuck to the screen leaving a horrible mess as you can see on the right. Also you will note it scratches very easily and is not opaque enough to look really white.
Liz’s special mix + 3 tbsp. opaque binder
Undisparaged we pressed on and then added 3 tbsp of binder to the mix, and then mixed it in with what was on the screen creating a probably about a 1.5 tbsp mix of binder. The results were again not great, but certainly looked better. At this stage we went for a new idea, we decided to use normal inks but try heat curing them, this is tricky as the melting point of PP is only 150ºC and the ideal curing temperature was some 280ºC!
50/50 acrylic / textile binder?
The first mix was a 50/50 between System 3 white acrylic ink and System 3 textile glue/binder stuff. This was much more opaque and seemed to be better instantly, we tried a high temprature cure without putting the heat press onto the plastic and nothing much happened, instead we dropped the temprature to a boiling 100ºC and used silicone release paper to stop it sticking, the results were good and the flaps were quite resistant to scratching too. I did a few test strips on real flaps to see if the heat press would smoosh the flaps out and cause them to become bigger, this didn’t happen however to get the scratch resistant finish desired I had to put it in for more than 90 seconds and they began to warp:
Scratch testing the 50/50 mix under various heat press durations at 100ºC
The final result of the tests with Liz were that I wasn’t happy with water based screen printing and the oil seems off the books for now, I had spoken to a chap called Chris Ratcliffe who advised using Apollo Inks or Screen Colours but it is all getting confusing and I think I need more help from Liz and others than I can really ask of them right now.
I am going back to my old system for now which is using vinyl stickers cut using a craft robo cnc cutter. The next thing is to get the beast back up and running as it’s been abused by students for 2 years and needs new blades and more no doubt!
UPDATE: Just remember that Liz suggested using Fujifilm Sericol Polydyne YD inks which I would have to buy, again like the others I don’t feel confident using them right now so I will hold off on screen printing as it’s just one more problem on the list of things in this project.