I think many people who pour glass plates use more emulsion than absolutely necessary and let it flow to the edges and then back to the container to be immediately reused for the next plates (or discarded, if you don't need to save on money).
Yes. Unhardened emulsions are very fragile, so be careful:When you said not to process over 20degC, I presume you are talking about dev/stop/fix after exposing the plates?
- not to exceed 20deg C
- not to touch the emulsion
- not to agitate vigorously, but gently
- not to use the combination of carbonate developer and too acidic stop bath, possibly creating CO2 bubbles?
- to dry it carefully, etc.
And, a hardening fix (possibly combined with a hardening (staining) developer) is recommended.
Emulsions hardened with easily available glyoxal, formalin or chrome alum should be much better (I'm using glyoxal), but still not the same hardness as today's modern commercial emulsions.
And note that adhesion and hardening are two totally different things! Good adhesion is a MUST and good hardening is a plus. For example, I think I once had hardening make adhesion worse, because the curling of the emulsion during drying was combined with stronger, harder emulsion that could pull the emulsion off the base more easily by developing a curl . On the other hand, it's said here that chrome alum also helps with adhesion with glass plates, but many people use no hardener at all.
Also, have you tried adding a very small amount of wetting agent (such as PhotoFlo) to the emulsion before coating? It could help the emulsion to run evenly if the heating of the plate is not enough to solve the problem.
I've never used commercial ones; just made some on my own. It's actually quite fun and I had great results without much work. Most of my tests have been just with food gelatin. Try the "Real formula" posted by PE here as a sticky topic, for starters... (Or get PE's book! I haven't had money to place the order yet, but soon it will become possible.) Also check http://www.thelightfarm.com/ , Denise Ross' site with a great deal of recipes and many different, home-kitchen like approaches.Are you mixing your own emulsion or using a commercial brand?