Most often the bubbles are from boiling monomer which nucleate on your tissue. You need to address ways of lowering the temperature. I would suggest:
- decreasing the volume of monomer polymerized
- lowering the concentration of initiator or catalyst
- placing the molds in a volume of water to act as a heat sink
- performing the polymerization under pressure (raising the boiling pt)

Obviously not all of these are practical solutions. Still, you should find a way of lowering the maximum temperature that the solution achieves.

Joe Tabeling
DDKJoe@aol.com

The bubbles are probably being formed during polymerization. I have seen this happen with Epon-Araldite and GMA However we did not use UV polymerization. We polymerized at 4o C in a vacuum dessicator and it eliminated most of the problem. Another trick that I used to use on tissues that had a tendency to float was to place a small amount of resin in the capsule, allow it to to partially polyermrize, place the tissue in the mold and then fill it up with the plastic resinand allow to cure. We also degassed our resin for at least an hour prior to filling the capsules.

regards
"Schoonhoven, Robert"
rschoonh.sph@mhs.unc.edu

Dear Nigel:
We have had a similar problem when polymerizing Lowicryl K4M in a UV chamber, probably due to too much heat generated during the polymerization. You can try reducing the intensity of the UV light, or use indirect light rather than direct light (if you have a foil lined chamber, put a foil covered baffle between the light and the specimen). A smaller volume of resin might also help (e.g. a smaller gelatin capsule). What works well for us is to use disposable polyethylene flat molds (available from E. Fullam, I think), overfilled with resin and covered with Saran wrap to exclude air.

Arthur R. Hand
Hand@nso1.uchc.edu