Casting process:

 

Casting is much quicker than hand production, however, it is still a lot of work! To give you an idea of what is involved, here's all that needs to be done (more pictures will come after my next round of casting):

 

Mold making:

  1. make original piece of jewelry
  2. make rubber mold of the original: For this, you have to use a special, uncured rubber, placing the piece in the material with a metal piece which will become the opening and 'sprue' of the mold. The sprue is the part of the model which wax silver will flow through to fill the model.
  3. The raw mold is baked in a vulcanizer. This is a type of heated press which compacts the rubber and cooks/cures it until it becomes hard.
  4. You then have to split the mold, and remove the original. This is done either by cutting the m old with an x-acto knife or by using a layer of talcum powder where you want it to split.

Wax models:

  1. Once you have the molds, you need a wax injection pot. This is a heated pot that you put special wax in. It has a nozzle that squirts molten wax into your molds to make wax copies of your original. Each finished piece is made from a separate wax model shot into the mold. The hard part here is getting the wax to fill the filigree design without overflowing between the wires. A small amount is acceptable as you can remove this 'flashing' if it is minor, but if it is not, it's back in the pot and you have to make a new one.
  2. Once you have a bunch of wax models, you have to inspect each one for imperfections, fix what you can or scrap them back into the pot.
  3. At this point, I have a few hundred models to work with, sorted by designs. A central wax 'sprue' or tree trunk is placed in a rubber base. At this point, I use a heated tool (wax pen, or in my case, I'm using a textile burning tool) to melt a pit in the trunk into which I can place the sprue of an individual wax model into to attach it to the 'wax tree'. By the time this is made, it actually looks like a tree made of lots of wax models. My trees often contain around 50 items, from small components to larger pieces.

Making the plaster molds:

  1. Once the trees are made, they are sprayed with a chemical that reduces surface tension and allowed to dry.
  2. Then a piece of steel pipe is fitted over the wax tree.
  3. a web of wax is placed inside the pipe but not touching the tree.
  4. There must be enough space from the top of the tree to the edge of the pipe to allow for at least 3/4 inch plaster and an air space.
  5. a special plaster is mixed and poured into the flask to cover the tree completely.
  6. air bubbles have to be removed from the plaster (investment), either using a vibrating table, or by placing it in a vacuum chamber for 2-4 minutes and allowing it to draw out the majority of the air bubbles in the plaster.
  7. After this is done, the mold is allowed to set for 1-2 hrs before 'de-waxing'
  8. This process is repeated for however many flasks you will cast.

Dewaxing and burnout:

  1. The name of this technique is 'lost wax casting' as the wax is lost in the process. You now have to get rid of all the wax in your mold. When your plaster is set, you remove the rubber base, which exposes an opening to the main 'trunk' or sprue.
  2. Most people remove the wax in the 'burnout' process, which means that the flask is placed over a receptical, in a kiln, opening down and the flasks are heated to 300 F for about 2 hrs (depending on flask size)...This can be rather messy and smelly, so I have chosen an additional step in my casting process which removes about 90-95% of the wax fumes. This is called Steam Dewaxing. To do this, you must have a steam dewaxing chamber, a machine with a basin of water under a wire or metal mesh and a heating element which converts the water to steam. The flasks are placed on the mesh, opening down, and steamed for a couple of hours. The wax then melts out and collects as a layer that cools when the steamer is turned off, allowing for easy collection and disposal.
  3. In any case, the molds are then run through a slow heating through a stepped process which brings the temperature of the flasks from 300 to 700 to 1350 and back down to casting temperature, in my case 1100. Depending on your flask size, this process can take from 8-15 hours. When the flasks are ready to cast into, the plaster is bone white and free of wax/carbon remains.

Casting:

  1. In my case, I am vacuum casting. I have a machine with a vacuum platform and a silicon mat where the hot flask is placed when taken out of the kiln. A vacuum is turned on slowly until it reaches maximum, and then the molden silver or other metal is poured into the flask through the opening. If all works well, the vacuum evacuates the air in the mold and pulls the silver down into all the nooks and crannies there in!
  2. You can either heat the metal with a traditional blow torch and crucible, or you can use an electromelt, which melts it to precise temperature before pouring. A flux (borax/boric acid) is put in with the silver and used to clean any gunk out of it.
  3. When you cast, you can use old or pre-used metals, but you must always have at least 50% newly refined metals or you run the risk of your castings becoming brittle/pourous.
  4. After pouring, the flask needs to cool for a few minutes and is then placed in a bucket of water to remove most of the plaster. You get what you see below:
  6. All the individual pieces then need cut or sawed off the tree and the rest of the plaster removed. Notice that the silver doesn't look very silver like, but is black. This is oxidation and it will be removed in an acid bath. When cut off, they look like this:

Clean up and polishing

  1. After they are de-oxidized and all the plaster is gone, the sprues have to be completely removed and files away, jump rings must be added to pendants, settings must be added where needed etc, and any bubbles that didn't come off in the debubblizing have to be removed from the models as they are now silver bubbles!
  2. Next, I put them all in a tumbler with medium grit ceramic media, then fine, the steel shot...if any of them are not polished well enough after the many hours of tumbling, I'll hand polish those on my polishing machine.
  3. Last comes the adding of earhooks or setting of gemstones.

As you can see, it's still a lot of work! And I do all of it! This is not some automated process done in India or Asia.....It's faster, but it's still a lot of work!