I didn’t mean literal sand, but my ignorance is showing. Plastic cups was the piece of the puzzle I was missing. I’m a bit surprised that size is large enough to shield against heat transfer, but again, I have no experience with silver and very little experience with aluminum in this area. Would still love to see a video of the pour, mostly for my own educational purposes, but also because melted silver is sexy.
Reminds me... Wasn’t there someone who made their own silver bars by melting silver in a wooden mold using a microwave back in 2012? These alternate DIY minting methods are cool.
Well you can use literal sand, I have about 100 lbs of sand that I sifted through a very find micron mesh, mixed with equally fine bentonite clay, called greensand that you can use for sand casting. I also have some oilsands called Petrobond that I'm going to try casting into as well. With it, I'm going to cast a pan out of copper, and then plate it very heavily with silver.
The plastic cup is just something to pour the plaster into. With the bread loaves, I have about a half inch of clearance on each side. The molds are typically one use only, so even if they crack, its not until after the loaf has been poured and started to cool enough that it wont lose its shape. I've got lucky and got two pours out of a single mold, but most of the time, the silver burns some of the detail away, so I dont cast a second time. I will certainly get a good video for you this upcoming weekend
Here is a little better of an example of mold making
https://i.imgur.com/LsfiCOn.pngThe stainless steel ring fits into the bottom rubber portion. The plaster will be poured in, and left to set. After that, when it dries, it goes in the oven, and the PLA will melt out, leaving a little tunnel to the cavity in the plaster. Silver is poured in, and then the sprue is cut off and the piece is sanded, polished, etc. Same deal as that youtube link I posted previously.
Also, I've done the microwave method before. Its obscenely dangerous. I disabled all of my microwave's safety features, increased the frequency of the "microwaves" by overclocking it, and it made the waves small enough to get outside of the microwave through the venting slits. Took me a minute to figure out why my face was getting itchy.
Do you have a investment vibrator to get bubbles out of the mold? You can get one cheap and also find good deals on centrifugal casting machines on ebay.