I've been searching craft stores and ebay for some sort of mold, either a neat silcone mold or a vintage tin soldier mold and had little luck finding anything I needed.
The other day Matt and I went to Lowes to buy some repair parts for a dripping faucet. As we left, we stopped at a "World Market" (Cost Plus) because I remembered they sold these giant-sized gummi bears there, and I wanted a giant gummi bear to use as a target for a shooting video. I bought one and it took me a while to realize the gummi bear was inside a clear plastic case. There was my mold for a mercury figure!
I bought 10 lbs of dry ice at a grocery store and had prepared the gummi mold, using duct tape to seal the seam of the two halves of the mold. I put the mold inside an ice chest that held the dry ice and began filling the mold with mercury with a syringe. After about 4lbs of mercury was inside, a tiny leak formed and the mercury started pouring out. Since mercury is SO heavy (dense for you science anal people) it tends to leak out tiny holes very easily, as water would do under 15 or 20 psi. I had to start all over again. I tried a few other things to try to seal it and then ran out of sunlight after a few hours.
I either had to abort the whole project or come up with a different way of doing the video. My dry ice was slowly "melting" away. I decided to just use ONE of the halves of the mold and filled that with just over 4lbs. of mercury. Had I used both halves of the mold the thing would have weighed about 9lbs. I left the mercury inside overnight and hoped the dry ice would hold out until morning.
I woke up and went outside to check on the mercury and there were just a few small pieces of dry ice left, and the mercury was partially melted. I really did not want to go buy more dry ice so I set the small clump directly on top of the mercury and after a couple more hours I checked it and it was solid.
I managed to get the mercury gummi out of the mold and it actually worked very well. The casting was very clean. I filmed it melting.
I'll probably get 1000 comments about "where do you buy mercury" and "you will die if you touch it!" and "it's the t1000!". People seem to have a great fascination with mercury and I just happen to have a LOT of it. (about 5x more than what I ever show on camera) Why not share it on video?