Friday, September 24, 2010
Your objective is to pour a mold that is thick enough to be a good wall in bronze but not too heavy because that is a sign of a poor bronze...so there is a very thin line of thinking there. It must be 1/8 inch thick to be a good solid wall but there are areas that you will not be able to control such as around ears or in detail areas.
I have one piece I pour that has a large indention in the middle and invariably I will have to pour a little wax over that area even after I have finished pouring the piece because it just is a high spot in the mold and hot wax just tends to run right off of it....therefore I let my wax cool a little just for that particular spot. If you take this opportunity to clean your molds and piece them back together for storage they will be ready next time. Wax does have a tendency to build up on your molds each time you pour a piece.About every three or four pours you should check your molds to see if age has deteriorated them or they need release.
I have had a personal battle with mice loving to spend the winter in my studio and they can ruin clay or molds in just a little time.
The wax that you poured from your mother silicon mold is cleaned of every defect and reconstructed if necessary (often feet or horns are cast separately) into an exact replica of your original clay.
Sometimes the texture of hair or eyes and ears catch little bits of mold material or bubbles requiring a good pair of tweezers and a hot dental tool.
There is also a harder red wax that comes in handy at patching. Always remember hot wax won't seal to cold wax so heat both patch and hole area. I use a small oil wick lamp to heat my tools but also have an electric hot tool with changeable tips.
I know the lamp sounds antiquated but it gives you time to think between heating your tool as to exactly what you are doing. You can not just go melting a cast wax, it is usually cast hollow so you can only touch it briefly to repair. You also must cut off your pour channels and patch that hole. I pour wax in a 1/8" or more thickness in a baking sheet to use to cut my plugs and fill pour holes, always heating wax to receive heated wax.
Notice the little piece of red wax holding the tail on the above buffalo, that will be metal but it is placed there for support and will be cut off in metal after casting. Also now is a great time to flatten the bottom to where it lays well on your base, I have a flat sheet of steel that I heat and carefully place my wax on to level the bottom and then clean.