This will be a short entry, as I'm busy burning out shells today.
I'm burning out shells for my students. Ceramic shells. You know, investment shells?
Okay, I'll explain. In teaching bronze casting, we use a technique called lost wax ceramic shell investment. The current technique was developed for casting complex metal shapes in the aerospace and automotive industry, like turbine blades. The method itself is quite ancient, so maybe using that motif as an explanation may help.
So, let's say you make a little guy, like say a voodoo doll, out of wax. And then you fashion a little wax funnel to stick on his head. Next you mix up a batch of slurry - muddy clay and horse dung with water added until it is about the consistency of pancake batter. Dip the little wax man in the slurry. Sprinkle with sand to make a a stucco. Let dry. Dip again. Repeat until a fairly thick layer, perhaps a 1/4 inch thick layer has built up. This clay layer is called an investment.
Build a fire. Place the clay and sand encased wax figure in the fire, upside down so the wax melts out. Fire until the clay is hard, until it becomes a ceramic. The ceramic is now hollow, it is like a shell. Turn it right side up, and pour molten metal through the funnel into the hollow shell. Allow to cool. Bust ceramic off. You have a little metal voodoo doll, which is kind of useless now as you cannot stick pins into him.
So, that is what we do in my class, but the materials are more space age. We used colloidal silica liquid and silica flour for the slurry. And fused silica for the sand for the stucco. I will put the student wax pieces, covered in ceramic, into our big gas kiln, and melt the wax out, then continue the firing to burn up the carbon residue. Thus, wax burnout.
So, while I am doing this, my thoughts drifted back to college. To the most idyllic time in college, when my older brother and I rented out a house at 712 E Hunter St. in Bloomington, Indiana. The house is still around. I google street viewed it.
The last time I talked to my brother, I asked, how long were we in that house?
"Seventeen... eighteen... years?"
"I know! It felt like that, didn't it? Two years."
The reason it seemed like such a long time, I think, is because we almost immediately regressed to the level of three-year-olds once we moved into the house. Every aspect of the house invited us to. It was a giant playland. The neighborhood was all college rentals, and so it was like small party village. The house itself had a large backyard, hidden from view by bushes and trees. It had a giant front porch, with two overstuffed couches on it. One was the regular couch, and the other was the bee couch. The bee couch used to be a regular couch, but then a bunch of bumble bees built a nest in one of the arms. We sat in it anyway and just left them alone - until one day a guest got stung, and then we got a new couch. The bee couch went into the alley and disappeared in about a half hour. The house had a spacious dining room and kitchen, perfect for entertaining. Somehow, I ended up as house chef, and made, you know, bachelor chow: beef stew, chili, spaghetti and meatballs, tuna casserole, stuff like that. I never had any complaints.
Most importantly though, the house had a Batcave.
No, really. The house had a basement extending throughout the entire foundation. The garage was in the basement, as was, obviously, the garage entrance. The backyard was elevated with respect to the garage entrance, and there was a limestone retaining wall which hid the garage entrance from the alley. Thus, an underground Batcave, which was how we thought of it.
The Batcave served a number of purposes. Obviously it was a garage, where we kept Elvis, our Ford F150 P.O.S. pickup truck, which resided there until it died of senile dementia. First it rusted out, and we replaced a lot of the skin with riveted sheet metal. By the end, Elvis kind of looked like a B-47 bomber. After Elvis left the building, my brother moved his VW station wagon in. The Batcave was still large enough for "hobbyist" activities, such as a, ahem, "greenhouse", a shooting gallery, a "chemistry set", a ping pong table, and still roomy enough to host the occasional "Viking Night".
("Viking Nights" occurred when a rare item was found abandoned somewhere around the city which was deemed interesting enough to destroy, like a TV, or a car. We would have various demolition tools available, and after preliminary festivities, my brother or I made more-or-less symbolic swipes at the the object, and then turned it over to the mob. Usually, at least one person was injured - collateral damage from overenthusiastic creative destruction, which is why we also had a first-aid kit on hand).
What else? Oh crap! We built a giant bubble machine one summer. We had stumbled upon a book at the library which contained a recipe for long-lasting soap bubbles (secret ingredient: glycerine). Not happy with making regular bubbles, we constructed a motorized swing arm witha rope at the end that dipped into a pan of soap solution, and then swung the rope in a big arc like a skip rope. We could produce bubbles that were three to four feet in diameter. We set a record on one calm and humid Southern Indiana night of about three blocks worth of giant bubbles cruising down the street - shimmering and wobbling down the street at about head level and moving at a stately walking pace. I think that caused an accident.
And I can't remember ever studying there. Honestly its a wonder I graduated with a halfway decent grade-point average.