We'll Always Have (Plaster of) Paris

Not bad glass for hot glue. My most successful "slush glue" casts on the right, one with an amber-colored bead inside.

I baked the first mold with Liquid Sculpey in it even though I was dubious that the heat would penetrate the thick plaster mold enough to cause the material to turn translucent. I was right about that but I was surprised that the mold survived and continued to be usable to experiment further all day. I am in love with Plaster of Paris now. The casts were coming out so flexible and easy to work with that I even tried the technique on some of the Ultracal cement molds for Kyra's body parts in case the whole puppet could be made with hot glue with wire armatures inside (TBD).

I followed Smarty Mike's tip about wetting the plaster before squishing in the hot glue into both mold halves. (How can that work? but it does!) Sure enough, the hot glue pops out completely, even in the undercuts, when cooled. I made several bottle test samples in this fashion and was feeling pretty Wile E. Coyote about the results. I was excited that they looked translucent and better formed than the build-up samples but wasn't too thrilled that they didn't look like glass.
Then, by accident, I pushed the temp on the hot glue gun to a higher level which caused the hot glue to become more liquefied which in turn caused me to have the idea to slush mold the bottles with it. I put less glue in and ran it around the mold leaving a thinner skin as I went. Which I have to report looks pretty darn glass-ish compared to the more dense solid version, seen below on the right.
I painted "ink" on the reverse of the various bottle halves, finding transparent marker ink to look the most like a liquid filling vs. a red opaque paint pen (shown in the middle, photographed next to real glass to see how the faux glass mustered.) On the right, you can see how the lower temp created patterns in the thicker bottles.

The only drawback was that I found it impossible to match and attach the front and backs of the casts to make a complete round bottle. If I pursue this solution for the film props, I may look at making the bottle shapes such that they can be one part molds. I found that brushing the outside of the cast with gloss medium clarified the surface of the mold.

ART IS LIFE QUOTE:
"Anything you do is craft until you master it."
--Otto Natzler (pioneering ceramicist)