Have used Peel a way molds for recycling the last changes of infiltration
mixture of MMA with polymethymethacrylate beads/BPO/dibutyl phthlate.  I
have also used them for embedding, just keep them attached with their
little piece of plastic between molds, put them in a flat container
of some sort and let them polymerize in a dessicator, you can pull vacuum for
a time, then release and polymerize at RT.  I did not use the molds for
infiltration step, they had a tendency to pull apart if heavy hands
dealt with them.

The recycling gig was to stockpile blocks of PMMA, perfectly square,
for the use that Linda described, to glue another block to the blank
block, made from last infiltration mixtures.  When you glue, you should
rough up the two surfaces coming into contact with each other, 600 grit
is good, then superglue. You will end up with a block suitable for clamping.

When I recycled this meant less to dispose of in a jar, messy procedure
discussed this last week.  I also did this to make prepolymerized layers,
in screw top plastic containers, whatever works best.  Best of all was
reduced and useful waste.  

To have a block large enough clamp, you will have to fill the mold to
capacity, or add more after first layers are done, great way to do
cross sections of femur, tibia, etc. with a very flat block face.

Ah the fun we boneheads have with plastic!

Gayle Callis