Cast Bronze Polycandelon Rings

I have been working on casting Bronze Polycandelon Rings for about a year and a half. I have been using a method where I make a wax model of my ring complete with sprew out of unrefined beeswax. I then make a clay mold around it with another ingreedient such as grass or wool which acts as a strengthener to help hold the mold together.

Right now I am just trying to get some of my information up here, so I am going to post some pictures. I will be adding information on medieval sources that talk about bronze casting as soon as I get the information together enough to post...

So far I have made four polycandelon ring casting attempts. I made a plaster mold of my wax so I could pour as many as I needed.

Cast beeswax model of polycandelon ring	The origenal wax with clay built up to what will be the "parting line" of the mold (the line between the two halves of the mold).

Making the plaster mold.	The outside surface of the plaster mold (marked so I can remember what it is a mold of since I have a lot of molds in my shop).

Attempt #1

For my first attempt I poured a wax mold, cleaned it up so that the mold lines and imperfections weren't showing, and built a clay investment about 1 inch thick all the way around it except for the opening which I used as a pour cup. I mixed cut straw with the clay as I built it up, leaving a thin layer of just clay around the wax to avoid flashing into the spots where the grass burned out.

Mixing the straw and clay.	Starting to build up the mold.

More building of the mold.	The mold flipped over so I can put clay on the other side.

The compleeted mold before it was fired.

Once the investment was compleat I let the clay slowly dry for several days, then I fired it in a kiln to harden the clay and burn out the wax.

The fired mold still in the kiln.	The fired mold buried in a sand pit and ready to pour in to.

I made a coal-burning furnace and with the help of my able assistant (dads are really great) heated up a crucible full of bronze. (There is a shop vac acting as a bellows substitute which you can't see in the pics.)

Me packing dirt and castable refractory between a barel and a spacer for a really simple furnace.

The smoke generated at the beginning of the fire before the coal burned down to coke.

Just after the crucible was placed in the furnace.	A nice hot fire and crucible.

We precariously managed to pour the bronze into the clay mold which we had placed in a small sand pit. Unfortunately, it was really hard to add coal to the fire without getting any in the crucible. We did skim the top of the bronze but were worried about keeping enough superheat on the bronze and managed to miss a piece of coal. This piece of coal got into the mold and caused the flow of bronze to plug up nd my mold didn't fill all of the way.

Partially cast polycandelon ring and peices of the mold.

Attempt #2

I had run out of time to let another clay mold slowly dry in time to have it ready by kingdom A&S so I resorted to a more modern and quicker investment method for my second polycandelon casting attempt. This involved using plaster and sand poured into a cylinder with chicken wire around it to form the mold, and once again burning the wax out. This attempt was also unsuccessful. While we were very careful about not getting coal into the bronze, I managed to not burn the wax out of the plaster mold well enough, and steam caused the mold to not fill all of the way.

Partially cast polycandelon ring #2.

Attempt #3

My th rid attempt at casting a polycandelon ring was mostly successful. I made another mold similar to the first one, but didn't have enough time to let it dry. The result was that there was some surface cracking in the clay which caused quite a bit of flashing, both in the cracks, and where the cracks connected to holes where the majority of the grass had burnt out. However, the mold did pour quite well. I also had this poured at Portland State University as part of a bronze casting class, so I could concentrate on my molds and not worry about the furnace issues.

The Mold set up in a "sand pit" created from a garbage can

The mold being poured

What it looked like before being dug out.	A picture of the bronze after I had broken away some of the investment. I can see the edges shining through letting me know it poured fully, but the large amounts of flashing make it hard to get the rest of the clay mold off.

Attempt #4

My latest attempt has definitely been my most successful. Instead of using grass mixed with the clay, I used cut up wool thread (a substitute for the wool clippings which are the recommended additive in the pyrotechnia). This had the benefit of not burning out large holes. It also just felt a lot better to work with than the straw. I allowed my mold to dry a bit slower than in the third attempt, but still cheated and used an old-style full head hair dryer to increase the drying speed (I am considering this a substitute for setting it in the warm sun as recommended in the pyrotechnia, since I live in Oregon and this was before our recent warm weather). I also put on a thin first coat, which didn't work terribly well for the polycandelon ring, but seems like it would work well for something that is a more solid and statuesque form. I had very little flashing and the clay mold broke apart very easily into a few pieces and the cast bronze just sort of popped out.

clay and wool thread	The mixed up clay and wool thread gunk

The gunk getting brushed on (later I just gave up and used fingers)	The finished bronze after I cut off the sprew but before I removed any of the flashing