Last weekend John was busy as all heck, giving a finishing polish to his Ordo Hermae and Bonisagus medallions. I remembered I'd taken photos of him pouring the molten metal months earlier, so I shot another photo of the finishing so I could show you the entire process that goes into these handcrafted treasures.
It all started with carving the mold. Here's the mold in progress for the Order of Hermes medallion. John created this design digitally and then engraved it in aluminum with a CNC machine, and used that as a mold for recycled plastic. In this image, he was testing the mold with play-doh.
Next up he took that plastic medallion, and pressed it into special petrobond casting sand to make temporary molds for the molten metal. Yep, that's a plain old cupcake pan.
Here's his backyard setup. On the left is his furnace, with the crucible full of molten metal sitting next to it. The crucible looks like a cup made of graphite, and is thoughtfully up on cinder blocks along with the furnace, so as not to melt our asphalt driveway. At center is the cupcake pan with sand molds, and at right is a bucket of water in case of emergency. Also notice John's industrial-thickness gloves, because the newly poured medallions are actually ON FIRE!
Let's take a closer look at how the medallions are actually ON FIRE! OK, actually it's the casting sand on fire. (This happens with the copper alloys, which have a higher melting point than the zinc used for most of the medallions.)
Exactly HOW HOT is the molten metal? EXTREMELY hot. This is Fahrenheit temperature, melting copper for bronze.
Don't be fooled by the lack of flames on these recently poured zinc medallions. They might still be liquid in this picture, and have a temperature in the hundreds of degrees.
The Bonisagus medallions were made by a slightly different technique: John made a disc from plaster of Paris, and then carved it by hand into a master form that he used to press the shape in the casting sand.
Left to right in this photo are the original scrap zinc, then an ingot he made by melting scrap, then the Ordo Hermae medallions molded in plastic, and finally zinc medallions cast in petrobond sand impressions made with the plastic medallions.
Finally, we arrive at last weekend's polishing frenzy. John used a rotary wire brush and sanding disc to take off misshapen bits, any casting sand, and bring out the luster of the metal.
Zinc will develop a layer of oxidation over time that gives it an antique look. You can accelerate the process by putting it in a pan of vinegar overnight; or you can reverse it with polishing/buffing/wire brushing, or going at it with very fine grit sandpaper. If you carry it around with your keys, you'll find that handling and friction in your pocket/purse will naturally develop a contrast between the low points that are gray with oxidation and the high points that are kept shiny.
Now the medallions are ready to send out to you, along with Ars Magica Definitive Edition!
