So last night I ended up smelling kind of like the smell given off when a match is lit. Mostly on my neck (washed my face, not my neck) but also on my sweater and t-shirt. Maybe heating the pieces to 90F is not so good.

Probably a good idea to have a separate set of clothes for da rANch. The problem with doing resin in the winter is that most warm indoor spaces aren't getting a lot of fresh outside air!

My original polyurethane casting still has an oily residue on the front surface. However, it seems that with the correct polyurethane and curing process, human contact should be okay. E.g. some of those kits use polyurethane, and it's also used in medical devices and condoms. I would think that proper curing to remove all the isocyanates would be essential. So maybe polyurethane deserves some more experimentation.

To do:


Both the large piece and one of the small pieces adhered to the paper cup. Definitely need more mold release (vaseline). The thicker thin piece was soft (almost gooey) near the top edges. I'm guessing that these were the coldest areas. One or two bubbles, mostly at the bottom where the paper cup joint was. For the most part clear with no visible bubbles -- maybe due to the more accurate mixing ratio?

The green piece with wire is a bit soft at the edges. Hopefully this will cure enough to be useful.

Definitely seems like temperature is a key factor. Forget which resin type, but read online that for that resin, after curing at room temp, a 16 hour cure at 150F is recommended.

To do:

  • find out if epoxy is supposed to "kick off" with exotherm in a cascading reaction or do a slower cure.
  • try the medium sulphur free clay
  • try Dragon Skin with embedded LEDs
  • think more seriously about temperature controlled ventilated box for multi-hour curing
  • get big box of vinyl gloves
  • get some acetone or appropriate fluid for cleaning uncured resin
  • bring polyester resin from house to ranch


Mixed using the 0.1oz scale. Can still be hard to get the proportions right.

Tried casting my thickest piece yet (1/2" thick). Had in toaster oven on low. Noticed some vapours coming out. Took piece out and it was hot to touch. Obvious that the chemical reaction was happening at a much higher rate. Self-heating was probably passing some critical threshold leading the surrounding resin to react. Not sure if this is the way it's supposed to happen. More research necessary.

Added some dye to the thick casting, but it was mostly set and the dye stayed mostly on the surface.


Tried casting with:

  • Epoxy
  • * Epoxy Resin Type 7132
  • * Epoxy Hardener Type 2001
  • * 2:1 ratio
  • * epoxy is less toxic during curing than the polys, but is a strong sensitizer
  • Polyurethane
  • * Smooth-On Crystal Clear (Part A)
  • * Smooth-On Clear Flex 95 (Part B)
  • * mixed it 1:2 instead of 1:1.5 to try to get shore A 40

I did some small pieces with embedded LEDs in the silicone RTV molds from before. The LEDs are pretty satisfying -- you can just see the dome. Really what you see are the wires and metal. The small pieces were mixed and cured outside. Temperature went down to 10C.

Also did some X-mas ornaments at the bottom of paper cups. These were cured inside (approx 16C).

The ones cured inside definitely came out better. No real surface tackiness on the epoxy, but it is kind of squishy at the edges. The polyurethane is slightly tacky.

The epoxy done outside is tacky and squishy at the edges. The poly is way goopy and not very good. These are currently in the toaster oven on low. This seems to make them more flexible while the temp is up.

Starting to think that a toaster oven setup with an exhaust fan might be an interesting idea. Could be used without the fan for toasting SMT boards.

To do:

  • get a scale and actually mix things with accuracy
  • figure out way to control temp
  • find something to use other than soft modelling clay -- it tends to smear over stuff and be hard to remove
  • investigate thermoplastic -- potentially less toxic than polyurethane/polyester
  • get some mineral oil -- use to dilute petrolatum jelly to reduce size of streaks
  • get some more dyes