Making a Sand Cast Bronze Sculpture

Here's a sculpture that I made a few years ago that combined cast and fabricated bronze. Bronze casting can be done in your back yard if you have a leaf blower and a small refractory furnace. Sand casting, in particular, is a fast and cheap way to cast metal.

Step 1: Start Making the Mold

Adding sand to the flask.  The flask can be made of metal or wood, must register well and be able to withstand the pressure of compacting the sand. 

Step 2: Pressing the Pattern Into the Sand

This pattern is made of wax, but patterns are often made of wood. The pattern will later be removed from the mold and bronze will be poured in the cavity created from the pattern. 

Step 3: Ramming the Sand

The sand needs to be compacted to hold its shape when the pattern is removed. Use a tool to hand pack the sand around the form until it is super dense. 

Step 4: Making the 2nd Half of the Mold

After the bottom of the flask has been rammed, talc is dusted over the surface of the pattern and sand to act as a release agent. 

Step 5: Adding Sand to the Flask

Put the flask together, sift sand over the pattern and evenly continue to add sand until the flask is full. 

Step 6: Ramming the Sand

Ram the hell out of it. Continue adding sand until it completely fills the flask. 

Step 7: Screed the Mold

Run a straight edge along the top edge of the flask to remove any excess sand. 

Step 8: Separate the Mold

Separate the mold and remove the pattern. If you did a good job, you'll get good detail and shape accuracy. If it falls apart, feh!

Step 9: Adding "Gates"

Channels, or "gates", need to be carved into the sand to give the bronze a way enter and fill the mold. 

Step 10: The Finished Mold

After the gates are cut into the sand, put the flask back together and you're ready to pour. 

Step 11: Make the Metal Hot

Heat the bronze to about 2,150 degrees Fahrenheit. Safety first!

Step 12: Pouring the Mold

Slowly fill the mold--this is the fun part. 

Step 13: Clean Your Casting

When cool, your bronze will easily separate from the sand but you'll need to clean it up a bit and maybe fix some imperfections in the casting. Sand blasting and wire brushing works great for making it pretty. Now you're ready to patina, or use the casting in a larger piece. 

Step 14: Fabricating

Beginning to fabricate the geometry around the casting for a wall hanging sculpture. Start by tack welding the forms together. 

Step 15: More Fabricating

Keep tack welding until the entire piece is together. Then weld the whole mess up, dress the welds (if you want) and make it nice. 

Step 16: Applying a Hot Patina

Clean the metal and then apply heat and chemicals: in this case ferric nitrate, cuprice nitrate and ammonium sulfide. This part is a little bit voodoo. 

Step 17: Finished Piece

Wax the sculpture with a couple coats of carnuba based wax and, presto, you have a bronze sculpture. Good luck!