I've been using photopolymer emulsion for the past 8 years...textile pv and graphic pu from sattichem, and i've tried ulano qtx (which i did not like). although both sattichem emulsions are suppose to be water proof once they are re-exposed I have started to have issues now that I am using my one arm press. It seems that the emulsion breaks down where the squeegee starts and on the edges of the paper...I was wondering if anyone could recommend a photopolymer emulsion that is water proof and hopefully available at Midwest. I am also wondering if this is something that is normal with one arm presses...I have just started using my tables one arm for printing big pieces and am still working out the kinks.
We use Murkami's Aquasol HVP. Pure photopolymer (comes in blue too, the P is for Pink) and it's pretty darned waterproof. I've used it for a community art center here as well and if you can water torture and abuse stencils worse than what those poor bastards get put through I'd like to see it. Proper and also post exposure is key of course. You can also request some diazo and drop it into the HV, gives it shelf life but is supposedly the way to go for supremo water resistance. They sell a reclaimable and permanent hardener as well to take it one step further. HV is high solids and geared for textiles so it might not be ideal for what you have going on. It can hold some excellent detail though.
I trialed Polycol Z and it was very, very awesome in terms of the detail it held and the buttery smooth stencils it made. Whole bunch of latitude for the exposure with the dual cures. The stencils had such a crazy smooth finish to them that it made hand printing noticeable easier and more consistent. I didn't give it the water torture test though. Ultimately, the exposures were too long for us so I stuck with the photopolymer. Kiwo makes a One Coat emulsion that's similar to HV and it's great too.
It sounds like Andy is getting at your EOM as being a contributing factor. If the stencil is thinner, that much less work the H20 needs to do to break through. Maybe try hitting the screens with a face coat on the squeegee side as well as the print side.
Oh and how bout rounding the squeegee corners?
And a last note on tape is that it seems to be a common misconception that taping the crap out of the underside of the screen is going to keep the stencil alive longer- it's not. It actually traps water up in there. I know that Andy was just suggesting a double taping at the problem areas which is a different concept.
My gut tells me you shouldn't need any taping and you really shouldn't need the hardeners to keep your stencil going for the whole run. How long of a press run are we talking about here?
BTW, I have just a little over zero experience with flatstock printing (that's about to change) but I think when yer talking stencils the fundamentals are the same.
I use the KIWOCOL PPZ with a varied outcome. On runs upward of 500 imprints it is toast. Using Plascharge additive only speeds up the process, and using a three part reflective ink drops the number of prints before breakdown to under 50. This is both with a single coat on both sides and a single inside double outside. We primarily use plastisol inks with Chromablue emulsion with no problems. I will ask some of our reps if the y have any reccomendations and get back to you.