In the past, I have experimented with
making keycaps out of resin with mixed results. It's something I want to continue experimenting with, but I think I need a different medium than resin.
So for my second foray into at home cap making, I've delved into backyard metal casting. I have plans of making about a dozen of these, maybe two dozen if I find a less intensive way to make them, to be gifted to people who have supported my ventures and just been all around awesome people to me, sold to help me be able to afford keyboard stuff and to experiment like this, and auctioned to help geekhack. As such, hopefully you can understand why I don't go super into detail about how I do things. With enough reading between the lines, you should be able to get some ideas on how to do it yourself.
Before I start going into details, remember that working with metal can be dangerous, so you need to use safety equipment, try not to breath the fumes, and carefully think about your steps of action in advance so as to minimize potential risks. I wore safety glasses, leather gloves, long pants, long sleeve sweatshirt, and leather shoes while doing this work. Ideally, I'd also have a leather apron.
To start, you'll need your special sand mixture, here's my bucket of special casting sand. I couldn't find as fine grade of a sand as I would have liked, but the sand is letting me make some interesting caps
If you do some research of your own, you can probably figure out how it's done and do some on your own.
After that, you'll need a form. For mine, I just used some cheap wood I picked up at Home Depot and glued and nailed them together with a nail gun. I find attaching guides to the side like I did helps a lot. You can easily make a form that's bigger than the one I did, but I wouldn't recommend smaller.
You'll use the form to pack the sand in and mold what you're casting. Once you get the mold made, you'll need to add sprues (vents to pour your metal and allow air and hot gases to escape) and channels for the metal to flow into your mold.
And here's my "crucible" for melting the metal resting on top of a fire brick.
You'll want at least one fire brick while working with metal. I lucked out on my "crucible" and found a small cast iron pot for cheap at a thrift store. This is fine for lower melting point metals like aluminum, pewter, and zinc, but not others out there.
To melt the metal, I use a propane torch. Ideally I'd be using an acetylene or oxy-acetylene torch, but I have to work with what I have in my budget. If you work with aluminum, propane probably won't be enough. It is fine for zinc and pewter though.
Once you get your metal melted, you'll need to remove some dross. Depending on your source for the metal, this may just be some oxidized metal or it may be impurities within the metal. After you remove the dross, pour it into your sprue, then wait a little bit. Break your mold apart, drop your piece into water and clean it off.
Here's my end result so far:
As you can see, it's not perfect, but I'm getting closer to finding a way to get a more consistent pour. The right side (not pictured) is less attractive because of the sprue and channel being on that side. I'm trying to figure out a way for the bottom to be the only part that's really affected by the sprue/channels. I went ahead and polished the cap and made the inside a little bigger. Next weekend I plan on prepping the inside for a stem and casting a resin stem in the cap. If that works out, I know I have a working prototype and I just have to figure out some more efficient ways of making the caps.
