New screen emulsion

Print Making
#1

I tried to do some screens using the new emulsion. The results were unsatisfying.

It looks like you really only need to coat one side of the screen as it’s so thin that it penetrates the screen fairly well. I coated both sides and could not get the back side to set on exposure. I also found that it didn’t set well with the recommended 54 second exposure time. I could see the image form, but all the emulsion washed out. This might have been due to the fact that I coated both sides of the screen.

#2

:54 seconds is the default setting on the exposure unit. Try resetting it to about 1m15s and it should work just fine with the emulsion we have.

#3

We just step tested the new emulsion last week with multiple timings, and set it at :54 as it produced the best results. We first tested at 20, 40, 60, and 80 seconds, and are still coating both sides as per normal procedure.

In our testing going above 60 seconds starts over exposing, and 80 seconds (1:20) makes it extremely difficult to wash out the stencil to reclaim the screen.

That was the correct timing for the old emulsion, which was fairly old and losing its sensitivity. The new pink emulsion is freshly mixed/sensitized, and is much faster than the old blue mix.

@ozindfw
We exposed and used two screens with the :54 settings successfully for the 4 color classes this past weekend, so I’m not sure where the problems are coming from.

  1. Try giving the emulsion a good stir before use, it’s possible it separates a bit since this new batch isn’t a premixed/presensitized formulation like the old blue mix was.
  2. Use cold, not hot water to rinse out the screen after exposure. Hot water can blast out even properly exposed emulsion before it has dried out for the first time after exposure.
  3. It’s possible that the screen wasn’t properly degreased and therefore the emulsion won’t stick properly.
#4

Thanks, I’ll give it another whack next week.

I’m pretty sure I had it de-greased well, but I may have reflexively used hot water.

How long did you let them dry for?

#5

Oops ok, I didnt know about the new pink emulsion. Thanks!

#6

No specific length of time, we just put it in front of the floor fan until it’s dry.

Also, make sure the water is running fully clear with no residue or foaming when you are cleaning off the screens prior to applying the emulsion. We’ve gotten caught by that a few times where there was leftover Bean-E-Doo, Strip-E-Doo, or other random contaminants from random stuff that was in the sink from other members projects.

#7

I’m up to 2 out of three working. Did three this morning. One still shows the issues I first mentioned, but the others worked out fine. The one that failed was the one I had to strip emulsion off before recoating I guess I wasn’t thorough enough.

I was both doubly careful about stirring the emulsion before coating, and about scrubbing and rinsing the screens before I dried them to apply emulsion.

There were some black flecks in the emulsion. I picked out what I could before application and had to pick some off my screen and touch up, but it all worked out.

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