Metal working!

AlyceInWonderland

I was just wondering what's best used to make molds to cast metal like Copper? My boyfriend would like to make metal objects of sorts varying in size, however, we don't know if clay would be best for the molds, and if so, what type of clay?

Thanks!

Betelgeuse

Casting copper (especially pure copper) is incredibly difficult. It has a very high melting point, and is prone to cracking. I can't see how clay will work, seeing as how the melting point of copper is almost 2000°F. I've never done any copper casting, but I'm pretty sure you will need specialized equipment for the melting and casting processes. Pewter might be an easier option to start with, since the melting point is only around 600°F, but of course I have to recommend doing this only under the guidance of someone who already knows exactly what they are doing, and in a proper setting with all the right equipment (like a metals studio)!

Improvolone

Unless someone has a background in this, I would recommend against it.

For general knowledges sake, I think I once saw a wax model made, essentially burried in sand, and when the hot metal was poured in the wax was destroyed and the metal filled it's space.

supabeast

Contact local art/design schools about jewelry making classes.

fuelish

Consider metal clays. They can can be worked like your everyday clay and then fired or even heated with a torch leaving only the metal. Pretty cool.

Here is one site

Or search: PMC clay, or metal clay

ilmmad

This guy in the Artist's Corner seems pretty good with metalworking. Shoot him a PM or something.

Forbe!

Casting copper is a poor idea. Copper alloys are better for casting.

What's a copper alloy? Brass, bronze, etc etc.

Copper itself melts at 1083C (1981F) at 99% purity.
Brass melts at 954C(1750F)
Bronze melts at 1030C (1886F)
Silver melts at 960.5C (1761F) at 99% purity.
Sterling Silver melts at 893C (1640F) at roughly 80% silver and 20% copper.
Gold melts at 1063C (1945F) but this also depends on the karat (22 karat being 95% gold).
The problem isn't necessarily melting it, but due to the thermal difference between the mold and the metal, the metal will lose heat extremely quickly and solidify. Because of this, copper tends to develop bubbles and fracture points where it cools too quickly. Copper casting is possible, but for a beginning endeavor, I do not advise it.

Silver, and Bronze are the best suited for beginning casting. Brass is also easy to cast, but it releases zinc fumes, which can be extremely hazardous. So a well ventilated area is needed.

Really, you can cast into anything. Ancient societies used carved rocks and sometimes wooden molds for arrow heads and other objects. The metal would be melted in a crucible, then poured into the mold. The most common method for jewelry casting is lost wax. A wax model is made, which will be what you want the final product to look like. A wax rod is attatched to this piece, and to a base.



Now the next part can be done many ways. Now that you have the wax model made, you must 'invest' it. This is where you surround it in some sort of heat resistant body that will take the negative form of your piece. This will allow you to 'burn out' or melt the wax out of the mold, leaving you with an empty channel where metal can flow into, and create the piece you modeled.

This can be done several ways. The wax model is usually placed in a metal 'flask' (pretty much just a section of steel tubing), where the sprue line is attatched to a button former, or rubber cap that attatches to the bottom. This forms a nice spout to go into your sprue line, which will help with the pouring of the metal. This can also be done with clay, instead of a button former. After it is all sealed up with a button former or clay, the next step is investing with plaster investment. Now listen here, this isn't normal plaster you can pick up at the hobby store. This is specially made plaster. It is usually mixed with a certain percentage (up to 20%) of gypsum, and other amounts of various other materials depending on the brand/purpose for casting. These extra additives allow the mold to be resilient under the high-heat of the metal. It also retains its detail and shape when being 'burned out'.

Too much information? Yeah, probably. I would probably go out and pick up Tim McCreight's 'Complete Metalsmith'. While I generally don't use this book as a primary source, the basics in there, as well as the casting information is a very good general outline.

Other than that, take a metalsmithing class. It is usually offered at most community colleges, and casting is a fairly common beginning skill.

In order to cast, you will need a minimum investment of:
An oxy-fuel or oxy-atmosphere torch.
A crucible.
Saftey equipment (tinted welding goggles, leather welding gloves)

Honestly it would be cheaper to enroll in a class to do this. The torch alone is about $200-$300 for the torch and gas tanks.

AlyceInWonderland

Thanks a bunch for all of that info, everyone. I just told my boyfriend that copper is out of the question. I was looking to take a metal smithing class anyway, I just wanted to gather some info and tips form people who have done this sort of thing before.

Thanks again!

Hypatia

As late as it is in the game, I just want to jump on the bandwagon to recommend a class. I've done this kind of metal working before and the amount of equipment/resources you need probably isn't worth it until he's had a chance to do it a number of times and really wants to go in for it.

A couple of things that aren't mentioned in this thread (although Forbe's is a really good summary) is that if he's planning on doing anything delicate or thin it's better to also have a centrifuge available for immediately after you pour the metal in. This forces the metal to expand into those really narrow places.

The other reason to take a class is because even if you collect all the equipment needed to do the casting, after you've cast you'll probably want to do some refining/polishing/etc which would require even more equipment. With the class, they'll already have all that stuff.