Catching Up Part 8: Pouring the Bronze!

Once the shells are completely dry they are moved onto the pour floor. The shell that has formed on top of the wax circles (remember back to spruing?) and top of the sprue bars are cut off with a saw to expose the wax inside. They are now inverted in the de-wax oven (autoclave) and are heated to approximately 900 degrees. The wax now melts and pours through the metal screen that the shells sit on and into the waiting container below. This way most of the wax can be reclaimed; when it cools it will be put back into use elsewhere in the foundry.

Please note the trough below the de-waxing oven; when the wax
is "lost" from the shells, it is collected here. The shells are glowing hot
at this point and will soon be inverted into beds of sand and ready to cast.

The furnace that Madd uses is an electric induction furnace, much faster and more efficient than the cheaper gas powered models. It sucks so much electricity that it can only be operated during "non-peak" hours or the energy usage alone would make casting cost prohibitive.

The bronze ingots are heated to 2,100 degrees then decanted
into a crucible.

 

You have to be a pretty good dancer to work on the pour floor. It's a three person job and the "dance" steps are carefully coordinated so that everything goes smoothly. It's a ridiculously dangerous job and you have to be completely alert as to your surroundings at all times. One slight misstep can be disastrous (oh the unspeakable horror I once witnessed many years ago; I try not to think about it). During one of my stints working a pour floor the interns sole job was to run along behind me and douse me with water or sand whenever my pants caught on fire. No kidding.

And. Here. We. Go.

 

The heat from the molten bronze is nearly unbearable and only the giant twin swamp coolers keep the room habitable. I had a pretty bad case of the nerves this day as so many things can go wrong at this step. If there is a major problem, that wax needs to be poured, chased, sprued and shelled all over again which is generally considered to be "a complete disaster". I was sweating bullets at this point but determined to keep my poker face on so the guys wouldn't be distracted.

In goes the bronze, out come the gasses. When the shell
is topped off, they move on to the next one.
 

The crucible is suspended by a steel bar so that both
men can better control the bronze flow.

Held vertically in place by the sand, the shells will need to cool down
now that the bronze is cast.
 

Note the bronze glowing as it cools down.

So far so good! Incredible job, guys!!

I must admit that I knew in my heart that everything was going to turn out great; there was no way that I could have gone through so much to get to this point to only have disaster strike. Still, the mind is a bag of snakes and I was pacing nervously like an expectant father.

Next up: we begin the knock-off and sandblasting to reveal the bronze Waterbearer. Stay tuned!