Few lifecasters take their work to the ultimate level of a real metal sculpture. It is expensive and time consuming work- but the results can be remarkable.
I have had the pleasure of working with a foundry in the process and I think its fascinating. Maybe you will too.
HOW IS IT DONE?
Typically a lifecast is a two part process: an alginate mold and a gypsum cement casting. If the casting is really something remarkable or memorable it might be worth taking it "all the way".
Do all necessary clean-up on the casting so it is exactly the way you want your bronze to look. Air bubbles and all other imperfections should be removed, and the edges should be cleaned up.
At this point, you should contact a foundry. They are pretty easy to find on Google and they can be found in all major metropolitan areas. If you send them pictures of your lifecast- they will ask you a few questions and will be able to give you a quote. Typically you would box up your lifecast and send it to them, but if its not far- I'd recommend driving it there yourself to avoid damage during shipping.
HERE'S WHAT THEY DO...
- The foundry will make a rubber mold of your lifecast. This can be a single-, or multiple-piece mold depending on the complexity of the lifecast.
- They then make a wax positive in this rubber mold. The wax positive should look exactly like your original lifecast (except the wax is usually brownish).
- They will use this wax positive in what is called a "lost wax casting" process. They coat the wax with what is called "investment". The wax is dipped repeatedly in the liquid investment and coated in sand. The investment dries between dippings and eventually a hard shell is built up about 3/4 of an inch thick. This dried investment is very hard and extremely heat proof.
- In a special oven, the wax is burned out of the investment. This is the final mold that the bronze is poured into.
- Bronze is heated in a crucible to approx. 2100°F where it glows bright yellow.
- The burned out investment is placed into a sand bed so it won't tip over and the bronze is carefully poured into it.
- The bronze cools from the outside in, so if a hollow casting is desired, the "middle part" that is still molten can be poured out leaving a relatively thin walled bronze sculpture.
- When the bronze has fully cooled, the investment is chipped off leaving the bronze sculpture behind.
- "Chasing" is the art of grinding off sprues, parting lines and other imperfections. After chasing, the sculpture is really shaping up.
- Optionally, you can have a patina applied to your sculpture. The founder will heat the bronze with a torch and apply various caustic chemicals that will oxidize the bronze to different colors, bringing out the details and giving it a beautiful old weathered appearance.
- This process can be done with other metals as well: iron, copper, brass, silver, gold- just about anything you want