I have been experimenting with epoxy resin and molds. I've bought two molds and I was not impressed. I have tried just about everything else with better results, including ice cube trays, silicone baking forms, plastic pill organizers, paint on latex rubber (you can pain around a domino and get a nice shape) and molds made with 2 part RTV silicone putty. The problem with the latter is, although it works like a dream, it gets expensive if you want to make anything big, like a bangle bracelet. You can buy a kit to pour a silicone mold (Sheri Haab demonstrates this on her video) only it will run about $34.00.
I was trolling around the Internet and I found artists who used silicone caulk to make molds. Some mix it with paint, some with water, some with glycerin and some apply it to a form in layers with no additives. I tried my own version: I got DAP 100% silicone caulk (not latex and no additives to prevent mold and mildew) and mixed it with a few drops of glycerin, added some cheap bouncy putty (you can get it at Oriental Traders for about $1.00 - they use it for kid's party favors) and I mix it in a metal pan with a metal spreader or spatula. You have to be quick because when it starts to set up, it goes fast. Then I smear some glycerin on my hands (Rings off or you can use gloves but it will stick without lubrication) and then build it up around the bangle (I've tried it with plastic and sterling silver bracelets) but leave an opening around the top so you can pour the resin. It can be small because the silicone will be flexible when it cures, but not so small you end up pouring resin everywhere but the mold.
You can pop out the positive after a couple of hours(you could do it sooner, but I like to be safe) and let it sit a day or two before using it. The silicone smells like vinegar. I wear a respirator and goggles. The mold ends up costing less than $5.00.
For the bangle you see here, I poured some resin and added metal leaf with a toothpick. Yes, it was messy. Then I dripped some alcohol ink and swirled it in the mold with the toothpick. I didn't want to mix it in entirely. I took it out after 24 hours and let it cure another 72. I used Envirotex Lite resin.
If you have ever finished a cast metal piece, resin is similar. You have to sand off the seams and odd flakes and then go to finer and finer grits of sandpaper. ( I started at 320 and ended at 2000). You can see every scratch in resin; it is not as forgiving as polymer clay. Then you can buff it. I read somewhere that stainless steel cleaner or Brasso helps to bring out the shine. I tried it and it does.
Resin cast in a hard plastic mold comes out shiny, but you have to finish the back. I still have not found a way I like to do that. That's another post, anyway.
Oh, and a great discovery!!! White vinegar cleans up uncured resin. Forget about the acetone and paint thinner. Vinegar is way safer and way cheaper.