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Having trouble drying handbuilt slabs of porcelain They are rather thin ( approx 1 & 1.5cm ) Have put them to dry sandwiched between two pieces of drywall And 80% have cracked in various places Any input would be GREATLY appreciated As is rather frustrating After so much trial and effort Luv Nicky 

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Hi Nicky,

I'm guessing the porcelain slabs are drying very quickly - the drywall absorbs water, yes? Perhaps slowing the drying down some would help.

1 - 1.5 cm (~1/2 inch), to me, that's on the thick side?

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What is it that you are planning to do with the slabs, Nicky, and what is their size?

Though the drywall will absorb water, you will probably find that the clay is sticking to the paper face of the drywall which, in turn, would cause undue stress on the slab as it shrinks. Rae's suggestion might help. Is there a reason that you can't dry them open faced instead of the sandwich?

JohnnyK

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One thing I found when I hand-built in porcelain is that drying is very tricky and that it needs to be really slow.

But some porcelains are much easier to work than others. So choice of porcelain is another thing you can experiment with.

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Between the drywall will help to keep them flat, but it will suck the moisture out quickly, might be too quick, or like others said, sticking to the drywall. Just as a test though, dry a slab with only drwyall underneath, and a couple sheets of newspaper covering the top; newspaper will slow down the drying a little by keeping airflow down. you can also mist the newspaper with a spritz bottle around the perimeter of the slab so the center and perimeter will dry at same rates. Maybe a bag draped over top will dry it a little slower still, and keep it flat.

How are the slabs cracking? Photos? Could be the perimeter is drying out first, and isnt flexing enough while the center drys and shrinks.

Ive taken plastic bags and used a rubber rib and a spritz of water on the clay to "press/cover" the slab with plastic. Ive done this on both sides of the slab, which allows me to do different things Ive needed it to. Plastic bags still breath and will allow the slab to dry, but slower. Maybe cover both sides with thin plastic (like kitchen garbage bags), and place in between drywall; drywall keeps em flat, and plastic keeps em from drying out too quick. If the plastic is put on nice and smooth (no wrinkles) it wont leave any texture in your surface, and will peel right off when you need it to.

Bigger, and thin slabs can be a nuisance no matter what kind of clay.

Edited by hitchmss

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My hunch would be it's not the weight of the drywall that is causing the cracking but uneven drying (unless you have a stack of these on top of each other). I think you need to slow down the edges drying faster than the middle of the slabs. I would try brushing some wax resist around the perimeter of them. After the resist has dried on one side place a piece of drywall on the tile, flip it over and wax the underside around the perimeter also. Once that is dry then put your second piece of drywall on top. 

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@Min@Gabby@hitchmss@JohnnyK@Hulk@Rae Reich

I don’t know if I have included all responses in this post Tried posting a photo but won’t accept You are ALL amazing Thank you SO much for your input What a wonderful community !!!

I had stacked the drywalls on top of each other Will def try all suggestions  ie with newspaper and plastic And mayb that have been drying to quickly 

I would like to make paper thin slabs  so quest it could all be down to timing 

Once again  thank you x

 

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Does anybody use a waxed paper or parchment paper "sandwich" instead of newspaper? If so, does it serve well, specific to porcelain?  Just curious-will test it out when I "finally" get my back-ordered clay. 

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6 hours ago, LeeU said:

Does anybody use a waxed paper or parchment paper "sandwich" instead of newspaper? If so, does it serve well, specific to porcelain?  Just curious-will test it out when I "finally" get my back-ordered clay. 

As I recall, waxed paper gets wet (!) and disintegrates/sticks/shreds. Haven't tried parchment, but it might do better. 

For thicker slabs to build stuff with, remember patterns cut from tar paper? The clay can be handled and manipulated (or kept flat) while it "adheres" to the tar paper. That might be a good solution for sandwiching slabs to dry slowly. Wouldn't stop cracks from sticking while drying, but might slow drying enough to preclude them.

Dry cleaner bag strips could be used to fold around edges   I like them because they don't retain creases that transfer.  

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When I make buttons or ornaments out of porcelain, I sandwich them between the sheetrock wareboards.  They do not have much weight, so I can stack 4 or 5 boards (9x9) in a stack, but once the work is mostly dry, I take some of the weight off because the bottom of the stack will break with the weight.   Yesterday I took an afternoon class where we were carving tiles.  The instructor used fabric, instead of paper between the clay and the wareboard.  She said when she is making tiles, she rolls out clay thicker, rather than thinner to prevent cracking and warping.  I do not bother with paper on smaller things because they dry very quickly, but on larger slabs I do use paper. (old telephone book pages)  I really wonder if your problem is because of very thin, large pieces of porcelain.  Would you be able to roll out thicker slabs for your purpose? 

Roberta

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