Burnout

The accretion of shell continues for 15 layers.

b_shellaccretion

d_shellaccretion

i_shellaccretionp_shellaccretion

The finished shells have their cups cut open to release the wax when it goes into the kiln.

a_burnout

b_burnout

They’re placed in the kiln, and fired up to 1500 degrees for 30 minutes to completely burn-out the wax and and any small wood pins used to support the structure sometimes. Now this is the true test to know that the shells are strong enough.

c_burnout

The wax doesn’t just melt out, it actually burns, which assures the mold is completely empty and dry, when the hot bronze is poured in later.  Any combustible material remaining in the mold during the metal pour could cause a dangerous explosion.

d_burnout

After the kiln has cooled, it is opened and the molds removed.

f_burnout

Everything looks great. No hairline cracks or flaws in the molds’ integrity. I had been worried up to this point, that the molds would be strong and sound.

g_burnout

H. and I are ready to setup for the pour next. The kiln stays nearby; we’ll preheat the shells again later when we pour metal, which is required to prevent a shock from hot metal hitting the relatively colder shell.  We move some fixtures around, and then, while digging a hole in the sand pit to place the molds into, I strain my back, which happens to me from time to time when I am not careful, unfortunately. So we must wait another week before we do the actual pour event.

What’s another week? My show’s still  six weeks off, so, why, uh, worry?

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