Chasing

Chasing is simply finishing the metal to look exactly like the original. The work is made or broken in this step. The trick is to reproduce the textures made in a soft material like clay or wax into the much harder metal. The real beauty of bronze is that although a metal, one can move it because it is one of the most malleable of the metals. The steps involved generally run as such:

Initial sandblasting to remove the bulk of the investment.
Cutting of the gating to about 1/4" stubs.
Sandblasting again to remove more investment.
Grinding down gating stubs near flush.
Removing flashing if necessary.
Fitting up for welding parts together.
Welding major sections together.
Grind, sand and texture welding seams and where gating is attached.
Fix any other casting defects.
Final sanding, texturing and finishing.
Blast in preparation for patina.

This is a shot of my blasting cabinet. To the right is a TIG welder and sitting on top is a plasma cutter. In the foreground is the welding table. These are some basic tools needed to begin the process. the work is put in the blaster and the shell is blasted off. It's tough stuff to remove, but we need to get it all off. The plasma cutter is a machine that generates intense heat to cut almost any metal. It is used to remove gating. Before we had a plasma cutter we used saws. This machine saves us hours of labor. The TIG (Tungsten Inert Gas) welder is used to weld the bronze sections together, fix defects and add texture. In the old days gas welders were used, but the TIG yields better results.

These are some of the tools used for finer work. From the top left: a small pneumatic belt sander called a Dynafile, a die grinder and a random orbital sander. On the bottom row from the left: a chasing hammer, chisels and punches, die sinkers rifflers and files. In addition, we use body grinders and sanders for rough work.

A shot of the recast section we blew out when the mold opened. This is before the part has been blasted. The white stuff is ceramic shell. At the bottom you can see two "stubs" where the gating was removed. On the right side of the section is a "fin", best seen as a white line in this picture. This is a casting defect caused when molten bronze flowed into a small crack in the mold. They are easy to remove, and are a common defect. In the old plaster investment days, fins were all over the bronze due to the tendency of plaster to crack easily and profusely.

Here you can see two sections that are being fit-up for welding. Each section must match up perfectly to effectively hide the seam. Usually the sections fit well right off the bat, but sometimes we have to give it a tap here and there to make a perfect fit. This is where cutting the wax in an irregular line comes into play. It makes the pieces fit like a jig saw puzzle and it also makes the chased line less likely to show.

A shot of the first welds, called "tack" welds. They hold the pieces together during final welding. When welding one works around the piece, welding maybe 3 inch lines and then moving to another area. This process is to reduce warping which would make fitting the next section more difficult.

In this shot you can see the bottom section has been welded and the weld beads are being ground off. After rough grinding, progressively finer grits of sand paper are used to make the weld flush with the surface. If there are textures that must be reproduced, they are done at this time.

The shiny section is where the texture has been applied to the bronze. This was a weld site. Die grinders, punches and chisels, hammers and files are used for this fine work.

I like to lay the work out and see what it looks like. It's been a long time since I've seen it together. Soon we will have it standing. The end is in sight.