peteyfrogboy (![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png)
peteyfrogboy) wrote2008-09-30 03:51 pm
peteyfrogboy) wrote2008-09-30 03:51 pm
Bronze Medal Project
I was approached some time ago by a friend of mine who wanted a medal cast in the 15th century Italian style. The medals I've done before have been something of a hodge-podge of styles, designed in the 15th century medallic style, at the 16th century medal size, cast in pewter like pilgrim badges. For this project I wanted to get as close as possible to the large bronze medals of Pisanello and his contemporaries.
I decided that I needed to make sure that I could actually figure out the technique before I accepted the commission. I still have a few weeks left to decide if I can do it. I wanted to make one for myself as a test to work the kinks out of my process, so I had to come up with an appropriate subject. My 10th wedding anniversary is coming up in November, so I decided to do a double portrait medal of myself and![[livejournal.com profile]](https://www.dreamwidth.org/img/external/lj-userinfo.gif)
adelavanbrugge.
If I was supremely confident, I would procure a piece of carving wax, carve and/or sculpt the master, and send it off for lost wax casting in bronze (I neither have nor am allowed to get the equipment to cast bronze myself, so the final step will have to be outsourced. I'm still not entirely sure where). I am definitely not that confident, so I decided instead to make a mold that I could use to cast several wax masters to play around with.
The equipment and materials I'm using aren't exactly 100% period, but I'm trying to stay as close as possible to a reasonable period technique (i.e. no rubber molds for me). The plan so far is this:
1) Sculpt each side of the medal separately in clay.
2) Make a plaster mold of each side.
3) Pour the wax master in the plaster mold.
The first stage went pretty well:
The base for each is a piece of plywood, marked the same to that they can be keyed with two dowels (actually pieces of chopstick). I tried using an air-dry clay the first time around, but there was so much shrinkage when the clay dried that the result was completely useless. Fortunately I did that test with just a flat round without doing any actual sculpting on it. The clay I ended up using is Roma Plastilina clay, in the extra-hard firmness. It's a non-drying plastiline clay that isn't really a period material, but I don't feel too bad for using it.
The plaster phase went pretty easily as well:
I built a box around each side with cardboard, sealing the edges with the air-dry clay. I also used that clay to make the gate and vents. I sprayed each mold box with WD-40 as a release and then poured in plain old plaster of Paris. Aside from a few small bubbles, the molds turned out very nicely.
The wax stage has been the most challenging so far:
I originally tried casting these with pure microcrystalline wax, but it was very soft and sticky. I added some paraffin (aka candle wax) to add some rigidity and make the surface less susceptible to fingerprints. I've been having quite a few problems with shrinkage so far, especially in the lettering. These pictures were taken straight out of the mold, and this is the best one I have gotten so far. I have since fixed some of the details with MC wax, and will use this one if I can't manage to get a better casting.
I have some wax on the stove right now getting ready to do some more experimenting. I first tried melting the wax in a small cast iron pan lined with aluminum foil. It melted fine, but pouring out of a pan is incredibly inaccurate and messy. I went to Goodwill and bought a small coffee maker for $2. The heating plate wasn't enough to melt all the wax, so I threw away everything but the carafe and have put that in a pot of boiling water. This seems to do a good job of melting the wax and allowing me to pour it accurately.
Stay tuned for more developments, and let me know if you happen to have any leads on a good bronze foundry in the Atlanta area.
I decided that I needed to make sure that I could actually figure out the technique before I accepted the commission. I still have a few weeks left to decide if I can do it. I wanted to make one for myself as a test to work the kinks out of my process, so I had to come up with an appropriate subject. My 10th wedding anniversary is coming up in November, so I decided to do a double portrait medal of myself and
adelavanbrugge.If I was supremely confident, I would procure a piece of carving wax, carve and/or sculpt the master, and send it off for lost wax casting in bronze (I neither have nor am allowed to get the equipment to cast bronze myself, so the final step will have to be outsourced. I'm still not entirely sure where). I am definitely not that confident, so I decided instead to make a mold that I could use to cast several wax masters to play around with.
The equipment and materials I'm using aren't exactly 100% period, but I'm trying to stay as close as possible to a reasonable period technique (i.e. no rubber molds for me). The plan so far is this:
1) Sculpt each side of the medal separately in clay.
2) Make a plaster mold of each side.
3) Pour the wax master in the plaster mold.
The first stage went pretty well:
The base for each is a piece of plywood, marked the same to that they can be keyed with two dowels (actually pieces of chopstick). I tried using an air-dry clay the first time around, but there was so much shrinkage when the clay dried that the result was completely useless. Fortunately I did that test with just a flat round without doing any actual sculpting on it. The clay I ended up using is Roma Plastilina clay, in the extra-hard firmness. It's a non-drying plastiline clay that isn't really a period material, but I don't feel too bad for using it.
The plaster phase went pretty easily as well:
I built a box around each side with cardboard, sealing the edges with the air-dry clay. I also used that clay to make the gate and vents. I sprayed each mold box with WD-40 as a release and then poured in plain old plaster of Paris. Aside from a few small bubbles, the molds turned out very nicely.
The wax stage has been the most challenging so far:
I originally tried casting these with pure microcrystalline wax, but it was very soft and sticky. I added some paraffin (aka candle wax) to add some rigidity and make the surface less susceptible to fingerprints. I've been having quite a few problems with shrinkage so far, especially in the lettering. These pictures were taken straight out of the mold, and this is the best one I have gotten so far. I have since fixed some of the details with MC wax, and will use this one if I can't manage to get a better casting.
I have some wax on the stove right now getting ready to do some more experimenting. I first tried melting the wax in a small cast iron pan lined with aluminum foil. It melted fine, but pouring out of a pan is incredibly inaccurate and messy. I went to Goodwill and bought a small coffee maker for $2. The heating plate wasn't enough to melt all the wax, so I threw away everything but the carafe and have put that in a pot of boiling water. This seems to do a good job of melting the wax and allowing me to pour it accurately.
Stay tuned for more developments, and let me know if you happen to have any leads on a good bronze foundry in the Atlanta area.
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