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PLAYING WITH FIRE 5

BRONZE CASTING PROCESS: POST 5


POURING WAXES

Once the original pattern has ben cut free of the molds, hot wax will be poured into the cavity where the original piece or part of a piece was removed. For the parts that need to be hollow, the wax is allowed to cool just long enough to build a thickness against the mold walls of between 1/8th and 1/4th inch. Most of the small parts will be poured solid and allowed to cool.

Pouring wax into the molds

Once the wax has cooled, the parts can be removed from the molds. They will need to be chased, or cleaned up, to faithfully reflect the original figure. At this stage the seam, where the mold was cut, will be retooled, along with any other obvious imperfections. Hot tools and dental picks are common tools of the trade in chasing waxes. So if you need dental work, but can’t afford it, you could do worse than asking a sculptor to help out.

Once the waxes look good, there will be “windows” to cut. Windows are sections of wax that are removed to allow the ceramic-shell slurry to coat the hollow areas of the form. The windows are cut with a knife, and saved to be cast, along with all the rest of the parts, and will be welded back into their proper place they were cut from, after everything is poured in metal. If I’m not boring you by now, you need to look into getting a hobby. I intend to go on like this for weeks!


Attaching the artwork to the tree

SPRUEING

When the waxes are all up to snuff, they need to be assembled on “casting trees”, These trees are also made of wax, as are the sprues or feeders that attach the artwork to the trees. Wax welds easily to wax, so building these trees is a matter of figuring out, roughly, how the metal will flow, and arranging the parts on the tree, much as the parts of a real tree are arranged. The artwork is the fruit of the tree, and is located away from the main feeder where it will cool first, pulling the molten metal away from the thick central trunk to provide a nice dense casting. After the tree is constructed, I spray the assembly with a surfactant to minimize bubbles in the slurry for cleaner castings.






Spraying the tree with surfactant, or de-bubbler


All Rights Reserved, David Crawford; 2019