My brother Toby requested that I create his wedding band for his upcoming wedding in May. He wanted a simple Sterling Silver band, and I've been wanting to try some sand casting so I figured this would be a good place to start.
My first task was to make the casting sand or "green sand" as it is known. I mixed a 50 pound bag of fine play sand with bentonite clay (kitty litter) and a bit of water. My mix was a little wet so the sand is a bit too sticky, but I'm hoping it will dry out and improve with time and use.
To practice a bit before I tried with the silver, I cast these two pieces out of some brass I had on hand, the bright yellow ones on the left being the new castings. I was relatively happy with these, it gave me a good idea of how much surface detail I could expect and how clean it might turn out. Now to make the ring.
To start with I have to make my master copy, which I carved out of wax. For this type of casting you can use anything really; wood, plastic, wax, or whatever is on hand will work. I used wax because it is very easy to carve and shape. I cut out this disk, carefully drilled a 11/16" hole through the middle, and smoothed and shaped it with files and sandpaper.
You can get a pretty smooth surface with this wax, I didn't go much past 120 grit sandpaper because the sand casting won't be able to give me any more detail.
Here's my casting frame. It's cast iron, with the two pins on one side fitting tightly into the holes on the other make sure everything keys back together cleanly. I got it a while ago with a lot of other random tools and haven't had a reason to use it. After a couple of uses now this thing is perfect for small jewelry scale castings.
To start I pack and ram with sand the bottom or drag frame.
I then flip it over and gently screw my ring master down into the sand a bit. Then it all gets coated with talcum powder which acts as a release agent between the two halves, and then set the cope or top half in place. Then more sand, carefully working around the ring at first, filling the top half and getting rammed in tight.
The cope and drag are then split apart and the wax master is removed. You can see that the sand stuck to other half and didn't pull apart cleanly, I believe this is due to the sand being a bit too wet. It does release nicely from the wax though so I am able to use it for the casting. I then carve a sprue or channel for the metal to pour into the cavity and carefully reassemble the halves.
When melting metal for a pour I build this simple little furnace out of fire bricks. It helps a lot to trap the heat and my little crucible gets up to temp much quicker.
My melting setup doing it's thing. I use a #4 Smith tip on my acetylene torch, melting about 15g of sterling silver casting grain.
Once it's fully liquidous I pour it right into the mold. Upon breaking it open again it looks like a success. The sand is knocked out of the mold and can be mixed back into the tub and reused.
Looking pretty good so far. The sprue gets clipped off and I'll start cleaning up the surface with some files.
Here's the ring after a bit of cleanup. You can see there are some large occlusions in the band where there was either some loose sand chunks in the mold or the liquid metal didn't quite fill it entirely. I'm debating giving it another try, the nice part of using silver like this is that if your casting fails, you can just melt it down and try again. All in all I'd call it a success, and hopefully it will only get better with practice.