Water-based clay pattern
First I create the piece I want to cast using water-based clay.
Glazed pattern in flask
This is yet another piece I used as a pattern after it had been glazed. The wood around it is the flask. Now I will pour sand mixed with epoxy in this “box” packing it tightly over and around the piece. It will be buried about 1 1/2″ thick.
Opening mold after second side has set up.
I will make one side, let it set up overnight, come back the next day, take the flask apart, flip the now hardened sand with piece over, re-build the flask around it, cover it completely with talc and then put another 2″ layer of epoxy sand over. The diagonal lines are cut into the first side and act as keys so that it will go back together just right.
Patterns removed from sand molds.
After both sides have set up, the mold is carefully pulled apart and the pattern is removed, creating the negative space the bronze will fill. The mold is cleaned up. In the case above I used wood glue to attach some of the pieces that broke when I pulled out the pattern. Then put the mold back together using the keys as registers to align, band it with metal bands, a band tightener and clips to hold it together when the bronze is being poured in.
Pouring bronze at the foundry
Pour team pouring bronze into molds at the foundry
The box in the bottom left-hand corner is the “cup” into which the bronze was poured. The thicker channel on the left is called the spru, the smaller channels leading into the piece are called the gates. The small protrusions from the ends of the piece are vents to allow metal to flow into the ends of the mold. Otherwise, metal would likely stop short, not filling mold and creating an unfinished piece.
Hot out of the molds
Pieces still covered with scale, gates and sprus still attached.
Partially polished bronze
The polishing process can take a long time. I’ve learned the right tools make all the difference.