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Steam Casting?

Jewelry Discussion
#1

Does anyone around here still steam cast? I have a few questions.

But first a little intro. I am just getting into casting and I don’t have a ton of money. Right now I can either afford only a burnout oven or a centrifugal casting machine on ebay (neycraft). The burnout oven is small but fits my needs as I’ll only be casting a little bit here and there and probably only a ring or two at a time in a 2 1/2 inch flask.

So I thought I would go for the oven and try my hand at steam casting. I have some info from Don Norris on steam casting as well here.

My questions:

  1. Why does the sprue network have to be so small to start? An 8 gauge wire split into 2 seems really tiny to have molten metal try and fit through as a sprue base hole. So why couldn’t one just pour the metal with crucible into a larger sprue base and quickly put the steam caster on immediately after? Would the metal definitely freeze doing it this way?

  2. Is a standard rubber base that I get at Rio Grande deep enough to steam cast? Apparently they are wanting for the investment to become the crucible. They are using a clay “button” to set the sprue tree onto. But wouldn’t just a standard rubber base work fine for the investing? I’m worried about water from the steam caster (probably just a tuna can and dowel rod) making the metal splatter all over the place.

  3. Can I get away with a bernzomatic ts8000? I know everyone says to go with an acetylene torch but i cannot because of money reasons at this time.

I have more questions but I can’t think of them right now. Thanks for listening to a noob.

#2

Altho’ I haven’t done any steam casting, I did investigate this rigorously at one time. There are some old posts on this here that lay out the process. You can also find some info in various old jewelry books…which are probably at your library or available from discoverbooks.cm for $4 each. Von Neumann’s book and McCreight’s Practical Metalsmith come to mind. As to your questions:

  1. The sprue is a maximum of 14 gauge according to McCreight. This way there isn’t any possibility of the metal flowing into the mold until you apply the steam pressure, which overcomes the surface tension of the metal, which keeps it in the little crucible you form at the top of the mold. If you make the sprue too wide, you’re doing gravity casting and risk the metal freezing somewhere before you can apply the steam pressure. Will it? Don’t know, but it is a simple matter to use the small sprues and use the steam pressure to do what you’re asking it to do, which is fill the mold all at once and give you good detail. When done right, steam gives very good detail.

  2. As to your crucible, yes, you can use a rubber base if it fits your tin can. The instructions specify a clay base because it may fit better and also allows you to make a larger crucible to fit more metal. When you mix investment, if your rubber base is loose, you may have investment all over the place and the clay makes a better seal. If the rubber base seals OK on your flask, then the only question is whether the hole at the top is large enough to fit all your metal. You can eyeball it or figure the volume of metal (you are going to have to weigh your model and figure the weight of metal to use as per any text on casting). Since you are going to be using a small flask for one ring, why not just use some clay to form the opening at the top? If the opening is too small, you can always carve it out to a larger size no matter what base you use.

  3. Yes, the torch you mention will melt at least an ounce of silver, maybe more. A simple ladies ring can be 3-4 grams of silver and a big gents ring as much as 10-14 grams, but in either case, because of the small, short sprues, you won’t go over an ounce of metal and maybe a lot less. Google “melting silver with bernzomatic ts8000” and you will see some videos of people doing it. You’ll also find steam casting videos. No guarantees people are doing it right, so watch more than one and compare with what you read.

As far as splattering, you should use enough water to moisten the paper or whatever in your steam generator (can lid with wooden handle) completely, but not enough that it drips water. That should take care of the splattering problem. Use an apron or some kind of protection and keep the can lid to the side of the flask to avoid any possible dripping and then at the last bring it down firmly onto the flask straight down. If there were any splattering, this would keep it off you.

Good Luck…royjohn

#3

Thank you for your in depth reply @royjohn! Much appreciated.

I bought my tin flask at Rio so the rubber base will also fit. I’ll give it a shot here soon and let you know. I still need to buy some more equipment :slight_smile:

#4

Thinking about it, you can easily cover the hole in the bottom of the base with your finger and measure the volume of water it holds. From this and the density of silver, you could figure the amount of silver (actually a little more based on the thickness of the rubber resulting in a larger cavity) that the hemisphere in your flask will hold. If you are using a 2 or 3 inch flask and just casting a ring or two at a time, you may not even need to carve out the hemisphere at all…you’ll just have to see. Could also measure the diameter of the hemisphere created and figure the volume by formula… -royjohn

#5

Thanks! I’ll keep that in mind! I’m having problems with my 3D printing wax right now so I am getting a little ahead of myself i guess haha.