This week at work I've been casting up standard oval sinks. It's a fun, labor intensive process using a method called slip casting in which liquid clay is poured into a plaster mold, allowed to set and then the excess drained to make a hollow object. Here's the process in action!
  1. Clean up the mold
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    Our sinks are two part molds- the bottom, which is pictured here and a top which is standard for all our sinks. The bottom mold can be changed for a different pattern like a sink with flowers or one that looks like bamboo. This weighs about 30 pounds and looks like a pregnant woman which freaks me out
  2. This is the top of the mold
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    It has the drain spout at the top where the slip is poured in as well as the back drain spout of the sink itself where the drain holes are drilled later so you don't over flow your sink and make a big mess
  3. Fill it with slip, let rest 1 hour and 45 mins
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    This is R2, our slip tank. He's filled with slip about every week from a bigger tank and then we roll him around and fill the molds. He looks and acts a lot like a gas pump and has a motor which stirs the slip and keeps things nice and liquidy. the slip has to weigh a certain amount and drain at a certain speed. If the slip is too slow and heavy, we won't get a nice thin, hollow cast
  4. Drain the excess slip and let rest 1-2 hours
    The plaster mold sucks up the water out of the slip and leaves behind solid clay. After it has set for an hour and 45 mins the clay is the right thickness so we need to dump out the rest. If it sits too long the plaster will keep sucking up water and the sink will get thicker and thicker until eventually it's solid not hollow. We drain the mold simply by flipping it over and letting the slip run out of the pour spout
  5. Pull the top off
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    Using a pallet knife we crack the top from the bottom and put in some plastic strips to separate the two sections of the mold. If the sink sticks to the top mold, which it always does, then we use an air hose with 120 lbs of pressure to detach it so it's sitting nice and comfortably in the bottom of the mold
  6. Sponge and let air dry till the end of the day, cover with plastic overnight
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  7. The next morning, using a special board and bands, flip and dump out the cast sink, upside down
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  8. Move it over to the wheel
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    This is our old Lockerbie kick wheel where all the holes are drilled and the mold is cleaned up. The sink has to be centered on the wheel so we know we're making the holes in the right place. This can take a long time but when it happens you feel like Rocky probably did when he ran up all those steps
  9. Drill top holes and flip over
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    The holes for the pipes to connect this sink to your home are made by hand using the spinning of the wheel and a tool with a needle point. The only way we know how big to make it is some tape attached to the handle of the needle tool so if we loose it were fucked. The element of danger is really exciting
  10. Drill drain holes
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    Once it's flipped over we re-center it on the wheel and drill these drain holes. We do it by hand and by eye so sometimes they are a little wonky but I've gotten pretty dang good at making them line up. If the sink gets cast too thick, the drain spout becomes solid and we can't drill these holes and the sink has to be thrown away. It's very sad
  11. Remove excess clay with metal rib to make drainage easy
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    The sink that comes out of the mold doesn't have the right angle to drain water smoothly. It ends up flattening out right before the bottom hole. This is to make getting the sink out of the mold easy on us but it means we have to go back in with this metal rib tool and make the draft right so water flows right on out of this baby and doesn't clog or pool. It's very satisfying
  12. Allow to dry completely, sand, bisque fire and send up to be glazed!
    This process in all takes 3 days and then 2 more to dry totally. Sometimes they are then messed up in the glazing process which can make you very sad since you put a lot of work into it. When they come out nice though, that sweet sweet Rocky feeling washes over you once again as you imagine some rich person clogging this beautiful sink with their golden hair balls