Wanted- a non tacky photopolymer emulsion

[Nation03]

I think Humidity is the issue, not heat. Screens dry in our shop overnight in the Winter without any added heat or dehumidifier and they are less tacky. Some emulsions are, by nature, just more tacky then others. The only time I've had the film sticking issue is when using Saati PV. Ulano emulsions just seem to do better in the heat/humid climates, IMO. This is the case for our shop at least. Everyone's work environment is different so results will always vary.

[tonypep]

The sticking is generally a chemistry issue.

While yes, humidity will always play a roll.  If you have eliminated the moisture issues, what remains is the plastisizers in the emulsion.  Under heat, these plasticizers are tacky and grab at all films.  Waterbase films exacerbate the issue compared to silver or laser films.

Tldr:  If your screens have an average of 35% internal humidity and they are still sticking during exposure, either change your emulsion or use baby powder/talcum powder.

This

[3Deep]

I agree it has nothing to do with drying the screen's in most case's, take Chromatech WR emulsion that stuff will stick a film in a heart beat compared to the CCI HXT.  I use both and found out that drying them both the same didn't work, so I dried the Chroma longer and still got sticky films, I think it's the solid's in the emulsions like Colin stated you can dry all you want and still get film sticking so break out the baby powder

[domineight]

The only other thing I can possibly think of regarding this issue that I might do differently, or which might be helpful is I've had a habit of leaving my inkjet film in the screen room to dry alongside the screens, pegged out on a curtain wire on the wall. There's no particular reason for me to do this other than it seemed the obvious place to leave my fresh wet inkjet film positives to dry. Often I might pull dry coated screens out the rack like drawers and throw my positives on top of a few screens.

Whether there is some voodoo involved in matching a dry stencil with an equally dry film positive to avoid this problem. Or another possibility is its the film positive itself that takes just enough moisture from the atmosphere and carries it to the stencil to react poorly and stick in the vacuum situation which I've never considered, but I've probably been lucky in avoiding that for the reason detailed above.

I don't use waterproof or water resistant inkjet film. I use the cheapest I can find. If it's dimensionally stable and works through my printer and costs less than someone else's roll I'll use it. I found no difference between any variant for the sticking issue anyway.

Oddly though, I know exactly when this problem arises for me and I can see it happening and avoid it.
It's only ever evident on the lower mesh counts - 43T and 59S mostly. You'll almost never see it sticking on a 90, 120, 150 (metric) regardless of how rushed you are.  Temperature here swings widely between seasons and I can enjoy weeks on end of 90%+humidity in summer.

What I find hard to accept, is a manufacturer will place product into the market that doesn't work. Especially our industry. Is an emulsion manufacturer really going to send product across the planet to all its resellers and not test it thoroughly? For something as simple and common as how it works with inkjet film? In all conditions?

Come on now, have a think about that.

[tonypep]

We use the Chromatech WR and yes it is sticky as all get out but I believe it was chemically engineered for CTS we don't care. Exposure=3 seconds

[ABuffington]

Photopolymers can be sticky due to the products used to make it and does have benefits.  Use a diazo emulison if you don't want any stickiness at all.  Baby powder solves the day and gets you a fast exposing emulsion.  We build our emulsions to be durable and have the highest resolution possible.  Sometimes that tack is important.  The surface tension of direct to screen imaging is better, the dots hold their shape.  Or if you are doing a 65 line with real film, the dots will be intimately pressed to the emulsion to avoid halation, especially in 10% and below.  Your inkjet printer to film rarely makes a good dot below 5%, thats why it is hard to image and why pure film has such perfect halftone shapes.  So Pure Photopolymers have less pinholing, less breakdown when shot well, and have tack that aides some printers and yes it will destroy an inkjet positive in hot humid conditions.  Keep your room at 70-75 degress and 35-50% humidity for the least amount of tack.

However, baby powder is such an easy fix for inkjet film users and photopolymers that you ought to try it!  No pinholes created, film peels off easily, screens shoot fast, and better edge quality.   

Al