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Showing posts from 2016

Casting the Medallions

Now that we have some wax models from the injection molds, it's time to turn them into metal. I do investment casting, which uses a gypsum "investment" to make the mold around wax models, which are then melted out. This is opposed to other forms like sand casting, where green sand (not literally green, but a fine sand that has been mixed with a binder, like water and bentonite clay for traditional green sand or oil to make petrobond) is packed into a frame around a model, then the mold is separated and the model gets removed by hand.

At a high level, there are four phases of investment casting:
Mold makingBurnoutCastingCleanup Phase 1: Mold Making The first step in mold making is to create a "sprue tree." Essentially, you're creating a system of pipes to deliver molten metal to your models. An incorrectly sprued model can get casting defects. 
If the sprue connected to the model is too small, the metal in the tube will solidify before the model does. This is…

Fox Masquerade Mask

I've had the idea of making a metal fox mask for a few years now, but haven't really had a reason to do it until this year. Work decided our holiday party would be a murder mystery masquerade, which makes a great excuse.

The basis for the mask was Wintercroft's Fox Half Mask. The half mask is perfect for the masquerade use, and I thought the papercraft/low poly look would translate well to the metal.
I took the mask template and glued it to 22 gauge copper sheet with spray adhesive.
Then after about an hour of work with a jeweler's saw... I had the pieces, somewhat resembling a fox mask, but mostly a Batman logo.
The paper templates were attached to the other side, so I could use the dotted lines for initial bends. These were mostly done on the corner of an anvil or over a piece of 1"x4" clamped in a bench vice. A rubber mallet was used instead of a metal hammer, since the rubber won't leave indentions in the surface where the hammer strikes.
After the i…

Wax Injection

Lost wax casting is a great process for jewelry because it captures every detail in your model (even fingerprints, if you're not careful). What's not so great is having to carve those details every single time if you want to make several copies of an object. To get around this, we can make a reusable mold and cast duplicate wax models to destroy instead instead of our nice master model.
Making the mold Wax molds are typically made out of some form of elastomer. Vulcanized rubber is a standard material for jewelry because of the durability of the mold. However, it also requires an expensive vulcanizer, and you may not need all the qualities of vulcanized rubber.
Instead of rubber, I use Mold Max 60, which is a RTV silicone. This means it can vulcanize (cure) into a usable mold at room temperature instead of needing a machine. Mold Max 60 specifically is capable of handling high temperatures, so while it's not the necessarily the best option for wax molds, I can also use it…

Making Metal Purple: Enamel and Patinas

One problem I ran into with my award medallion project is how to make metal purple. Because Calontir likes purple. A lot. After digging around, I came up with four possible plans:
EnamelPatinaDye-oxideDyed epoxy Enamel This was my first choice, as it both looks pretty and fits into the time period of the SCA. After some modifications to my soldering station and a promising test on scrap copper, I took one of my newly cast Golden Swan medallions and went to work.

A layer of enamel was applied and things looked good. The medallion was set aside to cool. While I was cleaning up other parts of the shop, I started hearing a faint little "Ting! Ting!" coming from the soldering tray. All of the beautiful enamel was popping off! Which lead to the first lesson from this project: coefficient of thermal expansion.
Most of the enamels you see for sale are "medium temperature medium expansion". These are designed with copper, gold, and silver in mind. Since the brass I was tryi…