I am having an issue with a "new" emulsion. It is Lawson's SBQ-510 Blue-Green Photopolymer. It is pre-sensitized and ready to use. In the past, we have been using CCI DXP Diazo-Photopolymer (pink) emulsion (from LogosSP.com) with very good results. However, the SBQ-510 is causing us some grief. Here are the specifics:
Coating 1/1 on a 110 mesh screen (I can't say for sure if it is a thick or thin coat)
Drying for about 30-45 minutes (air-cooled in a closed box)
Exposed for a variable amount of time (described below)
The exposure unit is a homemade enclosed box with 6x 40-watt plant UV bulbs about 6 inches from the glass.
The coating and drying seem to work fine. Even the exposure seems to work fine. I can see the image burnt into the emulsion. It's when I washout the stencil that I'm having an issue. When I washout "normally" (the same way I do with the pink), the emulsion seems to bubble and peel. And, it seems to take much longer to get the stencil to start washing washing out. I talked with a rep from Lawson and he suggested several things, specifically, the exposure time.
With the pink emulsion (which is not pre-sensitized), I expose for 5 minutes. I tried exposures of 50s, 2.5m, 5m, 10m, 20m, and 30m. All of these end with the same result.
I know it's going to be hard to diagnose the problem when it's a homemade exposure unit. I've even tried to use a calculator, but I am really confused by how this $40 piece of is supposed to tell me what the exposure time should be.
Does anyone have any suggestions on how I can remedy these issues? This emulsion is supposed to dry faster, burn faster, and stand up better than the pink. But, that's not what is happening. I would very much prefer to use it if I can get it to work right.
That sounds like a screen that needs to be degreased. I had that exact same thing happen to me because I spaced and forgot to degrease my screen. The emulsion bubbled out and peeled off when I sprayed it because it wasn't gripping the screen due to the residue left from the emulsion remover and dehazer. I re-cleaned the screen, degreased it and did everything else the same as I normally do, and it came out perfect.
Thanks for the info. I don't know about the degreasing. I thought (and I may be wrong) that the stencil remover had a degreaser in it. But, I will take the extra step and degrease the screen "manually". And, I will make sure I completely stir the emulsion before I coat the screen.
Another thing that might help is abrading the screen a bit before use - if it's a new screen, that is. It helps the emulsion grab onto the mesh better.
yup thats the last step you do when you reclaim a screen.
The degreaser I use is called CCI Nutralyze Screen Degreaser. You can water it down
so you dont have to use to much of it. Goes a long way.
I had the same type issue last week. Turns out that humidity was the problem bought a dehumidifier for my screen room also increased the exposure time. I would think that your emulsion is not dry.
We have a dehumidifier in the darkroom. The temperature/humidity is around 78d/40%. I don't know if that is optimal or less (probably less), but it doesn't seem to be a problem, at least with the pink emulsion. Our dryer is homemade. Basically, it's a cabinet with a bunch of PC case fans hooked up to a PC power supply. The idea is to have circulating air. Unfortunately, it is not heated, so that may also be contributing to the long drying time.
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The coating and drying seem to work fine. Even the exposure seems to work fine. I can see the image burnt into the emulsion.
With the pink emulsion (which is not pre-sensitized), I expose for 5 minutes. I tried exposures of 50s, 2.5m, 5m, 10m, 20m, and 30m. All of these end with the same result.
[/quote]
this is the part of your post that puzzles me...50seconds to 30 minutes and the same results????you never got one that rinsed out the entire coating of emulsion because of under exposure.....?????
it definately sounds like a degreaser problem up to this point
but this huge exposure latitude makes no sense
Hi, I very seldom post, just read alot!! But just had the same problem an with the sbq 510, Everything worked an look like it was suppose to untill I went to wash out. It was that the screens wasnt totally dry, they looked an felt dry but they hold moisture down in the fibers. I got a dehumidifier, fans an leave as long or over nite if possible. Like the sbq 510 now.
i could tell you that 1 and 1 on a 110 mesh is to thin, you need about 2 on front and to finish lay the back 2 more pases. make sure to lay screen face down on a screen rack. this will help make the imulsion thiker on the outer side of the screen. leavin a gap between emulsion and screen. Do you degrease your screens?
Emulsion issues 
