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Aussie John

Plaster bats for recycling clay. Newbie.

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I am new to ceramics and have recently started teaching art is a school two days per week.  The other art teacher is also not a ceramicist.  The current practise in the school it to discard clay ‘waste’.  This is loads of clay so I have been working on recycling.

I have dried discarded clay and rehydrated it for over a fortnight in a large bucket and made two large plaster bats to dry the rehydrated ‘slip’.

Two questions:

1.  Despite having been cast five days the plaster bats feel slightly cold to the touch - does this indicate they are still drying and not ready to use?

2.  I have used one of the bats to begin the ‘drying’ process of firming up the rehydrated clay over night and flipped it onto the second bat this morning.  All seems to be fine but the original bat now is damp from the clay sitting overnight.  I have more rehydrated clay to process.  Should I wait before sitting the next batch on the plaster and if so how do I know the plaster bat  is ready to use again?

Hope this makes sense!!

John

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1. Yes, plaster can take longer than that to fully cure. I normally allow new plaster items to cure for a week, but for a thick plaster slab it might take longer. Wait until they feel like room temperature.

2. Yes, the plaster slab will feel damp after clay has been sitting on it overnight. Normal! You can probably use it again right away one or two more times, but then give it a few days to fully dry out. 

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It could take a couple of weeks for the new slab to dry out. It wouldn't hurt to run a fan on it for a few days, or put it in a small room with a dehumidifier if you have one. Once it's totally dry, it will suck the water out of your clay much faster, and it will dry out pretty quickly after using it.

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Welcome to the Forums, Aussie John...Would I be correct in guessing that you live below the equator? If so, you should be in the summer down there and if so, your bats should dry rather rapidly compared to the Sacramento, CA area where we are at the beginning of a week of cold,rainy days. As Neil suggested, put a fan on those bats, or set them out in the sun to dry. When drying your clay, check the slabs frequently so they don't dry out too much. I'm doing exactly what you are doing with a bucket of clay sludge and trimmings (about 30 pounds worth) that has been sitting around for about 4 years with the lid on. I have 4 14" round plaster bats that I'm using to dry the clay enough to wedge. It's taking about 2 days before I can flip the slab of clay over, then another day or so before it is dry enough to wedge. Then I have to dry the bats with a fan before I can continue the process. Keep up the good work with the recycling of your previously wasted clay!

JohnnyK

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Thanks Johnny.  Once and Aussie now firmly settled in Northern Ireland after 20yrs here.  Aussie John is how I am referred to by some locals and seemed to suit as a user name!  Very damp and cold here just now so a fan in the house probably the best bet for drying the plaster.

I tipped the first plaster slab over the second and the clay came off as a single firming piece so I may be in a  position to wedge it today!

 

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Hi Aussie John!

Weather here 'bout the same as Sacramento, perhaps a bit warmer at night.

I cast four 9x13" plaster slabs (in rectangular cake pan - from the thrift store, as boss said "No" 'bout anything from our kitchen in clay, hmmph!) to dry clay on. They definitely work better when fully dry, however, they move water when dampened as well...

Any road, I'm propping them up on 1x1" sticks so air circulates underneath as well as around the four sides, seems to make a difference; the bottoms get cool, hence wet, eh?. I'm using one side for red, brown, black, and buff clay, the other side for white clay.

About half my 100 lb. bag of Pottery plaster remains, should get around to casting more bats and slabs, as the stuff don' last forever... btw, pottery plaster is the way to go.

A friend from Dublin tells me his son and their friends are mad for Sierra Nevada Pale Ale (that's from CA!); wow, when Guinness is the local brew? Gimme an Antwerpen!

Back to clay... I'm retaining all the sludge in a five gallon bucket, pouring off the clear water for other uses. The bits, lumps, cuttings - all hand-able bits go in a pan; when fully dry, into a bucket. When there's enough clay to make up about three gallons, I rehydrate the dry clay - fully dry clay turns to mush very quickly - add the sludge and just enough water, no more - mix mix with a grout mixer, then ladle out on the plaster.

In warm weather, the drying takes a few days or so; the batch I just bagged took almost two weeks - we've had cool and wet weather.

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(About half my 100 lb. bag of Pottery plaster remains, should get around to casting more bats and slabs, as the stuff don' last forever... btw, pottery plaster is the way to go.)

Hulk keep that bag sealed in plastic and in a very dry place as lumps will form in it with and damp air exposure. Air tight is best.I always buy it in 50#bags as it goes off for me in 100# bags before I can use it all. (next time maybe)

I keep mine in heated studio .

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