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I remembered this as a not-too-bad explanation of how to make an investment mold. I pruned 3-4 pages of emotional subplot, adverbs and indecisive qualifying clauses off of it. It’s still probably not done.

This started out almost twice as long. I haven’t edited much of anything I’ve ever written. Mostly because I’ve never really felt I’ve finished anything. Anything I really wanted to write anyway. I got A’s and B’s on essays I farted out without much of a second glance. Editing wasn’t so bad, just– a new experience. Recognizing mistakes, superfluous sentences. Kind of like chasing a bronze.

I’m going to make an investment mold today.

Investment (Lost Wax Investment, specifically) is a very old, and calculatedly insane, way of creating a cast metal sculpture.

Make an object, ultimately out of wax, which is called a positive. Create a pour cup, something like a large target to pour the metal into, that will become the funnel through which you pour the metal. Connect this funnel to the object via tubular wax pathways, known as gates, for the metal to eventually flow through. Connect more, smaller pathways, called vents, to the object to allow any trapped gas to escape.

Then create a cylindrical shell of a mixture called investment around the wax positive. Mix up the investment in a liquid form and pour it into the round flask. Investment contains plaster which will harden a few minutes after it’s poured.

Insert into kiln, raise temperature over the course of a day to 1000 degrees and hold for one day. Wax melts out; on the third day, you’re ready to pour metal. You’ve created a white cylinder with a void in it in the shape of your positive, pour cup, gates and vents.

For a small, hand modeled casting like one of the ones I’m making, this whole process, minus kiln firing, could be done in, maybe, twenty hours.

The insane part is that any number of small mistakes can nullify all your hard work. The flask around your positive meant to hold the liquid investment can burst, spilling all over the floor and ruining your wax positive. If you’re careless and make your flask too small, too close to your positive, it’ll crack terminally in the kiln at the thin points and when you go to pour, molten metal can hemorrhage through the walls of your mold. If the kiln gets too hot, your mold will break down and crack all the way through.

The calculated part is to do it correctly; so that none of these events will occur.

Some cracking is unavoidable due to the expansion of the melting wax within the mold. Flashing is the term for the metal that seeps into these cracks. A casting will come out of the mold with what looks like a varying number of common sea fins fused to its surface. These get cut off later, along with the gates, vents and pour cup, all solid bronze, a process known as chasing.

Investment consists of plaster and other ingredients. Investment recipes vary, like how different chefs have different ways of perfecting the same recipe. We use plaster, sand and luto. Luto is made of pulverized molds that have already been fired. It isn’t reactive to the water that activates the plaster and has refractory properties.

Mold making is incredibly dirty. Old molds don’t pulverize themselves.

We keep the luto in big red trashcans. The cans line a small portion of the foundry wall. I reach into one, and try to find the biggest chunks I can (they smash easier). I throw them on the floor where I will turn them into powder with a makeshift tool, which consists of a small piece of 3/8” plate steel welded to a four foot pipe.

Luto is not 100% necessary. In the absence of readily available old molds, one can simply increase his or her sand and plaster to a 1:1 ratio.

Plaster. By the end of the investment pour you’re covered in it. In both its dried and powered form. Why would anyone go through all this trouble?

Because you can cast anything this way. I’ve heard stories of people casting insects (with ceramic shell method) and getting the antennae in metal.

It takes me a little over an hour to get my materials and run some errands. Around 3:30 I start to make my mold.

I go into my studio and get one of my gated and vented positives and move it into the foundry where I will pour the investment. It already has a flask around it. A flask is a fancy name for a chicken wire and tarpaper tube held together with duct tape.

This is a relatively small casting. I chose it because I think I can do it by myself. It probably won’t take more than one ten-gallon bucket of investment.

Bad Jimmy and I are doing a burnout, the name for the high temp wax removal process, by ourselves. We were actually supposed to do this Sunday but he was nowhere to be found and yesterday, he had to study for an art history test. I’m tired of waiting for him so I have decided to make this little mold by myself.

I begin by making a thick plaster seal around the bottom of my tarpaper tube. This will hold the tube in place and hopefully keep about thirty pounds of sand, luto, plaster and water from spilling all over my boots.

I measure and mix the plaster. It takes a few minutes for it thicken enough to be effective.

With my hands covered in the stuff a mosquito starts to check out my arm. Like most people, I hate mosquito bites but I’m covered in plaster so I have no way of swatting it without making a mess. It lands on my arm near the inside of my elbow.

Fuck it.

I smash it but leave the outline of the heel of my hand on the sleeve of my t-shirt in plaster. It’ll harden. The stain won’t be gone after a trip through the washing machine but at least there’s one less mosquito in the world.

The plaster in my pail is starting to get thick. As the plaster reacts with the water, I feel it start to warm up. Chemistry.

I add more and more of the rapidly thickening stuff to the base of my flask until the seal is a good three inches thick and the plaster is essentially solid in my hands. All told this step takes about a half hour.

When I’m done my hands and lower forearms are covered in dried plaster. There’s no good way to get it off. It has a tendency to rip the hair off your arms.

I busy myself with other details that I can focus on while my plaster dries. While I’m preparing buckets of investment without the reactive ingredient of plaster, Bad Jimmy walks into the foundry. Not the brightest guy. He still hasn’t figured out his nickname means ‘limp dick’ to the people who thought it up. He hears it and thinks ‘Michael-Jackson-Bad.’ We shoot the shit a little, I help him get his flask together.

He gets to the point that he doesn’t need help so I decide I can pour another mold since he’s here. Twice the warm bodies to dump slush. I get another positive and flask out of my studio and proceed to support the base with plaster like I did with the other one. We need more material ready so I put sand and water in the four other available large buckets.
I’ve been careful to measure all the ingredients. Pails of plaster, luto and sand. I go a tiny bit light on the water. My investments have been a bit wet in the past. I have no desire to lose a week’s work to sloppy mold making.

We pour my molds first. The luto and sand have been sitting in ten gallon buckets at the periphery. The reactive plaster is added last and mixed by corded drill with a three foot mixing bit held in its chuck. It’s a heavy mixture. Quick pulses, sharp pulls of the drill’s trigger at first to agitate it, prevent it from spitting four cups of pale, white water in your face. When the particulates begin to be held in suspension, it’s smoother. Still heavy, thick, but it can be mixed more rapidly without fear of the drill making you look like the end of some niche interest porno.

Like the plaster base that keeps your flask from spewing, time is still your enemy. The lack of it though. You’ve got to pour this shit fast. And it’s surprising the geometrical deception that occurs when looking at a flask and visually comparing its volume to three or four buckets of investment. Better to err on the side of caution. Or use the pocket ref to calculate the volume of all the players and be certain. But I only did that once because I was low on plaster.

Limp Dick cum WHO’S BAD! cups his hands over my positive while I dump the first bucket into the flask. I dump it into his cupped hands which deflect the flow away from my positive and against the wall of the flask. It prevents the liquid mold material from knocking a vent or gate loose. A dirty job but I’m going to do the same for him shortly.

He’s got enough ingredients laid out for eight buckets. His casting isn’t that large but its byzantine design requires a large mold. He doesn’t have enough material prepare. Not my problem.

We repeat the pouring process. Hands cupped like I’m going to boost someone over a wall, looking into his flask, I immediately notice the wall of his flask is dangerously close to part of his positive. Thin walls breach when subjected to the pressure of liquid metal.

I don’t mention it. I want to get out of here. I’ve been here 3-4 hours. I also wouldn’t mind seeing a bunch of molten bronze shoot out the side of his mold when we go to pour. For– spectacle’s sake. The molds are 75-90% buried in sand for the pour, and the pressure of the sand can keep a potential breached bronze mold together. But fireworks are nice sometimes.

After six buckets are poured into his flask, I stop helping him pour, shift focus on preparing the ingredients for the extra investment that will be required to make his mold. Half a mold won’t get fired, much less make fireworks. I get the ingredients together for three more buckets. He says that’s enough.

We have to work quickly against the solidifying plaster. If the investment we’ve already poured hardens and we pour more of the wet stuff on it, it will create a parting line that will weaken the final mold. A parting line is created when solid and liquid plaster meet. The pressure from the liquid bronze within the mold can cause the two parts to separate. This would be a disaster. For my mold. But I prepared enough constituent material.

Pounding luto,measuring sand, measuring luto and water, mixing, in triple time to outpace the chemical reaction and it’s unknowable speed.

During this final frantic part of the process, Juah walks in. She starts to prepare a two part resin bonded sand mold. Far enough away from us that a tsunami of liquid investment from a shitty flask won’t ruin her mold. Causing her to commit adrenaline-augmented, justifiable homicide. As an accessory, I don’t know if I could dissuade her from also pounding my head into the foundry’s cement floor.

The three extra buckets I made prove to be just enough to envelope Jimmy’s piece. The older mixture doesn’t harden, forming a parting line. But the bottom of the mold is a little too close for comfort. The sculpture department’s own Archimedes decides to raise the level of the investment by displacing the still liquid mixture with four ordinary red bricks. The fire bricks that the burnout kiln is made out of would expand less during firing. But they’re a bit coveted around here (READ: if our professor saw fire brick stuck in a mold he would assault Bad Jimmy verbally to the point that his first born would be lucky not to be born deaf). He says, I think I’ll be able to get the out.

Juah, on her knees pounding resin sand, looks at me skeptically. I look at her in a similar fashion. Probably, I tell him with a shrug.

Again, not my problem. There’s a pizza place with a large one topping for five dollars on Tuesdays. I think I’ll get one and eat the whole thing.