Recycling old plaster molds
Posted 12 April 2013 - 02:01 PM
I know that warming up cast plaster (about 40 -60 °C) will make evaporate the water added and make reusable the plaster for new castings.
Does anyone has already made such operation? Is it advisable to do?
I did some molders, but they did not result well, so I have to throw them away, but it's a waste!
Thanks for any advice!
Posted 15 April 2013 - 06:33 PM
you will have to figure out how to crush and mill the solids down to a powder (and you'll never get a consistent powder like commercial plaster), then there is the question of the integrity of the plaster assuming you have success in recycling it. you can do some research on the hemihydrate/dihydrate state of plaster, and how to achieve it. i think you need to hold the plaster above 300*F for a long period of time. personally i'd rather just spend $20 vs wasting hours of my time, but that's just me! good luck and let us know if you try it out!
Posted 15 April 2013 - 10:19 PM
now the cool part - for every "production grade" mold they take, there are possibly several molds that got scrapped and they have to do something with....outside in their yard are 2-3 "piles" of baseball-size chunks of cured plaster. piles are roughly 15+ feet tall and maybe 30+ ft diameter (the size pile you see at the end of a conveyor moving dirt, i guess). the material gets loaded up and they truck it down to San Diego, where it gets turned into gypsum board/drywall. pretty cool, right? some pretty nifty recycling IMO.
Posted 18 April 2013 - 01:04 PM
FYI, the clay they use is a Lincoln Fire Clay based body for most of the work they produce, since they have a huge clay pit down the road. I know they make their own chunky grog (like 1/8" chunky) from all the reject sewer pipes (I think the factory might even be L.E.E.D. certified since they recycle EVERYTHING, I only mentioned the reject plaster pile - you should see the reject greenware and fired clay piles!!!) - which I'm sure helps tremendously for making the thick work they produce. All the pipes are extruded under crazy amts of pressure for uniformity! I'm sure there's some other clays in the body, like kaolin and ball clays. Not sure if they need any flux/feldspars in the body at the temps they are firing to, but I'm sure there is some in there. They have a laboratory on-site with employees who only work on clay bodies and glazes formulation/testing.
I'm actually supposed to be heading out to Lincoln on May 18th, as I was invited to carve sewer pipes during Clay Fest/Lincoln Clay Day. As far as I know, it's the ONLY way to get your hands on a leather-hard sewer pipe and some of their raw clay -- they only do it for this one day a year, for one local artist's ceramics class (Ray Gonzales, who helped start Feats of Clay). If I remember, I will try to ask Ray if he knows anything more about the clay body. If he doesn't know, I can ask Eric at Sacramento IMCO, since they might buy all the other materials through them.
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