Bronze sculpture by Iron John Logan. Original WIP posted on Art of Weapons Facebook group Maker's Challenge June 2019
Finished piece can be seen here "Boar Spear" 2020 (irontreeforge.com)
My paper sketch and the block of plaster I am going to carve it into
carving complete. Now to make a negative of this
Negative plaster cast from the carved plaster
Brush the negative plaster with hot wax
once cool the wax pops right out of the negative plaster
made two of these waxes
Wax cleaned up inside and out
Two waxes welded together into the finished wax pattern
the wax pattern gated. Gating is the art of attaching sprues, vents and risers to first let the wax escape and later let the molten metal in. There is a lot of science and art into gating, understanding hot and cold spots in the pattern and how to elevate shrinkage and other defects
Once the pattern is gated and, in this case, caged for protection, it is time to build up the refractory shell - which will be the final mold when completed.
Multiple dips in refractory slurry and dusting with fused silica "stucco" builds up the shell refractory over the course of a week between drying between coats
Once shell is complete and dry the bottom is ground to open the wax so it can escape during burn out. You can also see here how thick the shell is.
wax pouring out of the bottom of the kiln
Shell covered patterns are then placed in a 1650F kiln for de-waxing
Shell de-waxed and fired, ready for metal!
Foundry heating up
pulling the crucible
Shells filled with molten bronze
Once cool the fun part begins - de-shell. All your hard work the weel before to build up the shell now has to be jack-hammered off...
patina process (urine)
Continued working of the urine patina for over 1 year and officially released "boar Spear" in 2020