Screen Printers Open - A Forum for Screen Printing and Embroidery

Possibly not exposed for long enough.

If you are seeing the pores clogged up on a "clean" screen then they are not being cleaned properly. Do you leave ink in your screens or do you clean them out after printing? If you leave ink in the screen for several days you will have to dehaze. What are you using for degreaser?

If you are not processing many screens a day I would recommend a pure photopolymer emulsion for the simple fact of shelf life. Diazo and dual cure emulsions have a 3-6 week shelf life roughly as opposed to a pure photopolymer that can last up to a year.

Another thing to try if you are using a halogen light is to change the bulb every year.
They get weaker and you can't really tell unless you replace.

The emulsion I used is the speedball brand I think ... I'll look at the container again tonight.   The emulsion has stayed in the fridge, so no it did not freeze.  Unfortunalty the dark room shares the boiler room, so it is quite warm as far as setting the emulsion in a cool place.

I will have to look at the degreaser tonight too ...

We exposed the screen for 70 sec ... I don't know the age of the bulbs because I just took this over for someone who abandoned and isn't talking ... I will look tonight and see what 'type' of bed it is.  It has a nice aluminum frame, glass top ... probably 8 bulbs, with a purple glow when running.  I know things can change, but the screen I made a month ago from this emulsion dried dark green and the new screens that had problems were more of a sun faded john deere green.

Prosperi-Tees, we process about 1 screen a month right now, not very many. Do you have a pure photopolymer brand recommendation?

The previous person left the ink on all screens and tools ... we have found a couple cans of screen opener, which is what I am supposing she used to reuse the screen instead of cleaning. 

Inkwerks, yes the plugs are 'thinner' emulsion that ran back into the washed out areas, it even has a green tint to it just like, the dried emulsion. 

The screen we had problems with had no ink on them, they were brand new being washed out for the firs time. 

It could be under exposure since I have no real guidlines yet, but I keep going back to it worked at 70 sec a month ago perfectly ... wouldn't that imply the emulsion or degreaser?  We mistakenly tried 300 seconds a couple of weeks ago!  That was over exposure, it would even think about washing out!

No one seems to think the degreaser was the culprit, so I will mix some new emulsion tonight ...

Yes I stirred the emulsion prior to use.  If i remember right we mixed the emulsion in sept., so it sounds like it is old.  Unfortunate, the bottle is only half gone.

Ralph mentioned Saatichem Textile PV.  Killer graphics you mentioned one part emulsion ... brand suggestion?  Any other suggestions on emulsion brands with long shelf lifes?  That won't give a beginner too much of a fit?

I have been using a pure photopolymer for about 6 months now, its Xenon Plastofast. But will have to go to a dual cure for running waterbased discharge. Even with a hardener the Plastofast does not last long for discharge but for day to day work with plastisol the Plastofast works just fine and its only about 50 bucks a gallon.

Since you are starting out I would do one thing, "Do not cheap out". You will find in this industry that it pays to do it right and spend the money on the good stuff. I know that you were handed most of this stuff so see what you have and maybe throw up a list so we can see whats crap and whats worth using. Since you are new there is no need to fight and mess with products that may or may not work. Hope that helps.

Ok, some clues were found in your post.

Speedball emulsion, 70 seconds exposure, 8 lamps, mixed emulsion in Sept. Keep in in the fridge.

You problem indicates classic under exposure. Slimy emulsion and scum in the open areas.

Ok, not sure about the speedball emulsion but if you mixed a powder substance with warm water and then mixed that into the emulsion then it is duel cure emulsion and will have a shelf life of about 6 weeks at normal room temperature. If kept in the fridge you should get about twice that self life. Again this is with most duel cure emulsions but I cannot say if it applies to the speedball stuff.

On the possibility that the emulsion is not bad then when you took it out of the fridge did you let it sit until it got to room temperature before you coated the screens? Just asking as the cold emulsion will naturally make a thicker EOM on the screen and someone new to coating screens would not really notice it or know how to control it. A thicker EOM would mean you need to expose the screen longer and thus you would end up with an underexposed slimy screen is you used the same time that worked for you before. Multi-Tube exposure units are not powerful enough to overcome the slightly thicker EOM in just a few seconds like a strong single point exposure unit could.

When applying the emulsion this list time did it look like it was starting to get lumpy (best way I can describe it)? If so then it has exceeded its shelf life.