Friday, July 17, 2009

Processing Reclaim Clay

If you're like me you probably end up with a fair amount of scrap clay and slurry by the time you finish making pots. Reclaiming those scraps is a simple process that requires just a little bit of time.

Materials needed: a 5 gallon plastic bucket and lid, a plaster block, a turkey baster and a ladle.

For the plaster block purchase 25 pounds of pottery plaster or regular plaster from a hardware store. Follow the mixing ratios and directions designated for that particular type of plaster. Whatever dry plaster is left over you can store in a lidded bucket, make sure to save the ratio and directions before throwing away the bag, been there, done that. When handling dry plaster always wear a respirator.

There are many ways to create a plaster mold. An adequately sized mold for the home potter is a USPS flat rate box, free from the post office. Cut off the top of the box and cover all the corners and seams inside and out with duct tape. Working on a level surface, take a board as wide as the box and cover it with a thick layer of newspaper. Place the USPS box on top of the board and pour in the plaster leaving 1/2 to 1 inch headroom. Gently lift and drop the board under the mold to tap the air bubbles in the plaster to the surface. Allow the plaster to set up overnight before removing the cardboard box. Now you can take a scraping tool to carefully clean up the sharp edges. Don't worry about the cardboard that sticks you can get that later. Place your new plaster block in a well ventilated area with a lattice underneath so the air can move around it. Two 2" X 4" will suffice. Let the block dry for 1 1/2 to 2 weeks. Using a damp green scouring pad refine the pores of the plaster block with a little bit of elbow grease. The green scrubby will also remove the remaining cardboard from the surface. Place your block on top of two 1 inch furring strips or the like for constant ventilation and to prevent mold growth. I designate one side of my plaster block for white clay and the other for red clay.

Now the fun part, processing reclaim.

Step 1- Designate a 5 gallon bucket with lid to one type of clay for reclaim (cone 02 red terracotta clay)

Step 2- Add all red terracotta clay slurry from the wheel and slurry water containers to the recycle bucket.

Step 3- Completely dry all large clay scraps before slaking them down in the recycle bucket (this will allow a more uniform slurry).

Step 4- Allow the clay and water to separate overnight. The heavier clay particles will sink to the bottom.

Step 5- Using a ladle, gently scoop out as much water as you can. With a turkey baster you can suction off the remaining 1/2 inch of free standing water if you so choose.

Step 6- Carry your bucket to the plaster block and give it a good stir. Using one hand, repeatedly scoop out as much clay slurry as your block can handle before pouring off the sides and making a mess.

Step 7- Wait. Depending on the humidity in the air it may take up to 2 days before your clay is firm enough to lift off the plaster block.

*Here you can either continue recycling or wedge your clay for reuse.

Step 8-Wedging up your reclaim, roll the clay out into thick coils of even thickness.

Step 9- Using your coils, create a framework around the plaster block. Make certain to secure the coils to the base of the block on the inside, outside, and joints.

Step 10- Fill the coil framework with clay slurry.

By creating a coil frame you can recycle more clay at one time. As the slurry dries it will sink from the edges of the coil frame, simply push the top edges into the slurry to keep them moist. When the slurry is firm enough, pull it away from the plaster and wedge it up for reuse or store in a lidded plastic bucket to keep it moist for the future.

NOTE- Never use a sharp scraper to remove the clay from the plaster block. Plaster and clay do not mix. If it does, the plaster will pop in the kiln leaving behind pitted pottery and ruined work.

1 comment:

Dirt-Kicker Pottery said...

Great post. My reclaiming process is very similar to yours. Have you tried adding a teaspoon of vinegar into your 5 gallon bucket? It takes a couple weeks, but it really helps the clay with plasticity.