Josh Calcino and I were in Japan on a holiday recently, and we spent a fair bit of time in some of the larger crystal shops they had in Kyoto - we both collected crystals when we were younger. We saw some beautiful pieces of bismuth, and I came close to buying some.
Instead, we decided to buy some raw bismuth when we got back home and make the crystals ourselves! So we went ahead and ordered 3kg of bismuth. What I’m holding below is roughly a kilogram chunk.
The good thing with bismuth is that it melts at temperatures you can reach on a stove top. So we sacrificed a small steel container, melted about half our bismuth in it, and then suspended a chain made from linked staples into the top of the bismuth, to provide a site for nucleation of a crystal as the bismuth cooled.
To get larger crystals, the trick is to cool the bismuth slower. So we decided to try and insulate the sides of the conatiner, which is where most of the heat is lost. To that end, we grabbed some playing sand from Bunnings, and used it to form an insulating barrier around the full 3kg of melted bismuth.
We’ve had lots of issues with the top cooling too fast, and forming a solid layer that we cannot penetrate, so I think we might buy a cheap butane torch so that we can melt the top if needed.
This is so far the first and only crystal we’ve been happy with that we have produced.