Hi, I'm using Speedball Diazo Emulsion. I bought it and sensitized it on December 3, and have kept it mostly in the fridge, although it may have been left out for a night or two. It originally worked great.
Now, however, after the image washes out, little holes and sections of the emulsion start to disappear all over the screen, especially near the image.
Is the emulsion expired? It still looks pretty green and turns blue after burning. Any idea how to fix this? can I add some more sensitizer so to not waste emulsion/money?
Sounds like it went bad, unless your under exposing your screens. however That's too short of a time period for it to go bad. I wouldn't add more sensitizer, you should have used all that came with the product. Did it specify to keep the emulsion at fridge temp? Possibly you sensitized it incorrectly, for example used cold water instead of hot.
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When mine starts doing that I shoot it longer. My last batch (not the same brand) I started shooting for 3mins and when I finally gave up on that batch I was shooting it for 6mins
Bummer on that time line though -
yeah, i already tried overburning it...i used to burn for 30 minutes at 16 inches with a 250 w light...i keep going up and it keeps happening. last time i burned it for 1.5 hours!
Most diazo and dual-cure emulsions are only good for about a month. Some seem to be able to milk a little more time out of them by refrigeration, but if you're not using that much emulsion you'd be better off buying a pure photopolymer emulsion like Ulano QTX or Saati Textil PV. They'll last a year or more.
I would not recommend photopolymer emulsion to anyone with a lo-tech setup unless you are prepared to execute exposure time to the second.
If you are careful, you can split up batches of Diazo emulsion by weight. In a darkish room split in half the emulsion and sensitizer separately. Sensitize each half batch of emulsion (with half the water of course) seperatley when you want. Unsenstized diazo will last a year or so.
I have done this several times successfully with Ulano FX88
I switched to Chromaline's Chroma/Tech PL while I still had a 500w halogen shoplight/foam/black felt setup, and while it dropped my exposure times down to a slim 7 minutes from 18 minutes using a dual cure emulsion, I can assure you I didn't have to dial in my exposure times to within a second. I've got a 1200w metal halide exposure unit now and, while I expose for "light units" instead of seconds, and I'm using Ulano's QX-1 hybrid emulsion which has quite a bit of latitude for a pre-sensitized emulsion, even now 1 second one way or the other will make little difference in all but perhaps the most demanding halftone work. For someone who's using Speedball's diazo emulsion and suffering from exposures so long that he probably has to shave again before the screen is done, the chances of him having huge problems with a pure photopolymer emulsion are unlikely if he'll do a step-wedge test to determine some base exposure times for the different meshes he's using.
But that's just from my experience.
question about expired emulsion 
