Nicky S Posted February 16, 2019 Report Share Posted February 16, 2019 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 Link to comment Share on other sites More sharing options...
Rae Reich Posted February 16, 2019 Report Share Posted February 16, 2019 They could be sticking to the drywall as they shrink and dry. A sheet of newspaper above and below slabs will help. Or non-woven interfacing (Pellon). Don't (if you were) stack layers of drywall/clay/drywall/clay. Too much weight. Link to comment Share on other sites More sharing options...
Hulk Posted February 16, 2019 Report Share Posted February 16, 2019 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? Link to comment Share on other sites More sharing options...
JohnnyK Posted February 16, 2019 Report Share Posted February 16, 2019 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 Link to comment Share on other sites More sharing options...
Gabby Posted February 16, 2019 Report Share Posted February 16, 2019 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. Link to comment Share on other sites More sharing options...
hitchmss Posted February 16, 2019 Report Share Posted February 16, 2019 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. Link to comment Share on other sites More sharing options...
Min Posted February 16, 2019 Report Share Posted February 16, 2019 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. Link to comment Share on other sites More sharing options...
Nicky S Posted February 16, 2019 Author Report Share Posted February 16, 2019 @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 Link to comment Share on other sites More sharing options...
LeeU Posted February 17, 2019 Report Share Posted February 17, 2019 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. Link to comment Share on other sites More sharing options...
Rae Reich Posted February 17, 2019 Report Share Posted February 17, 2019 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. Link to comment Share on other sites More sharing options...
Roberta12 Posted February 17, 2019 Report Share Posted February 17, 2019 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 Link to comment Share on other sites More sharing options...
Nicky S Posted February 18, 2019 Author Report Share Posted February 18, 2019 @Roberta12Thank you for your input Think my dry wall boards might be too heavy And will def try material and newspaper as alternatives As really would like to keep them as thin as possible Thank you nicky Link to comment Share on other sites More sharing options...
Marcia Selsor Posted February 20, 2019 Report Share Posted February 20, 2019 the newspaper also allows the shrinkage movement to occur reducing braking. I do this with y large raku slabs 25" x 18" Marcia Link to comment Share on other sites More sharing options...
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