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Timbear3

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Hi, I am new in this forum and I am here to learn from you guys. I started playing with terracotta clay and I love to work with it. I am trying to make a very thin (about 1/16") uniform rectangular sheets. They are about 5"x6". After I take out the air bubbles I cut with a fine steel wire the sheets and place them on a thick steel flat surface dressed with a very fine oil film. I cover them with an acrylic sheet with some weight on it to keep them flat (very important) for a few days. Then, when they are easy to handle I found first they are bent or curved up and cracked and I can't burn them that way. Please tell me what I am doing wrong if not all. Thanks.

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roll them with a rolling pin and two guide sticks that are your desire thickness. Do this on paper or fabric on sheet rock.Keep the edge of the sheet rock from shedding plaster by putting wide tape over the edge. After you cut it to the right shape, drop it on the floor or table just to jar it to set. Put under wraps to dry slow. You could put another piece of sheet rock on top to keep it flat. (tricks from Elizabeth Priddy) I do this for my small tiles and they stay flat.

 

Marcia

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I agree with Marcia, roll out your clay to the desired thickness on top of a piece of canvas, lay a piece of drywall on top of the sheet, flip it over so it now lays on the drywall with canvas on top peel off the canvas. Drop the drywall and clay sheet on the floor to settle the clay. Trim it to the size desired without lifting or manipulating the clay in any way. Put another piece of drywall on top of the clay so that you now have a sandwich of drywall, clay, drywall. Put this somewhere out of the way and allow to dry, don't mess with it. Your sheets of clay should dry flat. The important thing is to never lift a flat sheet of clay once you have dropped it to settle or you will get warping in my experience.

 

Once it dries flat when you fire it use either silica on the kiln shelf or clay disks to raise them up off the shelf so they can shrink without curling in the kiln. Some like to fire them standing upright but I have not tried this upright method yet I always use clay disks and never have curling from firing.

 

It takes some experimentation to find the techniques that work for you good luck and keep at it and you'll get it done.

 

T

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Thank you both, Mrs. Selsor and Pugaboo. Its glad to hear about your experiences and today I think I am going to get some drywall to follow your advises. Only I need to know  for how long  do I should keep the tiles drying before burn them? And can I stack them inside the kiln? Thanks.

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Mrs. Oldlady My country is the USA, and I learned this on the internet while watching people turning the terracotta clay and making excellent pieces of table. It’s a great art!

 

What I am trying to make it an experiment. I heard that using terracotta clay there is a way to cool the interior of the vessel because of its permeability to the water and the evaporation of the water requires energy that lowers the temperature of the outside and inside of the container. I want to experiment in a different way with this phenomenon. I am curious,  that’s all. Thanks

 

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My first question to you is ... What are those lumps and discolored pieces that show up in your images? Have you mixed something into your clay?

 

To make ordinary flat pieces you can just slice pieces of the clay and roll them flat between two rulers or boards. Cut to size. Slide them sideways onto a board to dry ... do not touch them at all until they stiffen up. Again ... Do Not Touch Them until they are stiff.

 

Terra cotta is usually a very forgiving clay that should be quite friendly to work with. Good luck!

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I am no expert, but my friends who make tiles immediately place them between two pieces of drywall and allow them to dry that way to avoid warping.    another thing i have heard is to cut your square but leave the excess edges in place and allow to dry without removing those edges.  keeps your square edges from drying out too fast.   also . allow tiles to dry on newspaper which will shrink as your tile shrinks; thereby avoiding curling.  good luck.    rakuku 

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What I am trying to make it an experiment. I heard that using terracotta clay there is a way

to cool the interior of the vessel  because of its permeability to the water and the evaporation

of the water requires energy that lowers the temperature of the outside and inside of the

container. I want to experiment in a different way with this phenomenon. I am curious,  that’s all.

 

The idea certainly works. However those instances I've seen have been made out of

quite chunky pottery, so I'm interested in why you are looking at thin sheets.

 

[The need for evaporative cooling in the UK is quite low. However do I remember UK

milk-bottle and butter coolers from my childhood (when milk was left on your doorstep,

and before fridges were common.).]

 

Peter

 

PS I did a few quick googles

 

The traditional Spanish ‘botijo’

http://www.notechmagazine.com/2012/04/botijos.html

... includes an experiment keeping water cool in an oven, and a ref to an old technical paper.

After 7 hours in an oven at 39C the inside water was at 24C. Wow!

 

A modern product

http://www.stwerburghspottery.co.uk/potsforsale/kitchenware/terracool.html

... note the use of a glazed saucer to stop the water leaking onto the supporting surface

 

Architectural building-scale use

http://www.phdc.eu/uploads/media/PHDC_Cooling_with_porous_ceramic_01-06-09.pdf

 

PPS

AFAIK paper-clay seems to be the body of choice for those making really large, really

thin sheets, often 'cast' on plaster from paper-slip. (Paper-clay dries more evenly, and

has greater green strength.)

 

 

... afterthought: I assume that there would be problems with long term use in hard-water areas.

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Thanks to all of you. A lot of information about what I am working on.  Today I just made my first sheet and we will see how I did it.  I didn’t  make for the corners as you mentioned, I didn’t know.  On next sheet I’ll.  I picked the terracotta material thinking that was no other clay that had that porous property.  Looks like you have to diy knowing the recipe. They mention Feldspar, Kaolin and silica. I am planning to apply this technology to the electronic field. Again  thanks to Mrs. Chris, rakukuku, Mrs. Selsor, bciskepottery  and Peter for your guidance .

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I learned not so long ago by a very experience potter that using guide sticks is not so good. Apparently, when you use them, the rolling pin pushes the clay that's only on the surface and not all the inside as well. If you want to use guides, you should put them only at them end, when you're close to the thickness you want. But at first, just roll it pushing gently on one side, flip it over, repeat. This way the clay is properly flattened in and out, and it limits risks of warping and deformations.
I haven't try it out myself yet, but I think it is worth a try  :)

 

roll them with a rolling pin and two guide sticks that are your desire thickness. Do this on paper or fabric on sheet rock.Keep the edge of the sheet rock from shedding plaster by putting wide tape over the edge. After you cut it to the right shape, drop it on the floor or table just to jar it to set. Put under wraps to dry slow. You could put another piece of sheet rock on top to keep it flat. (tricks from Elizabeth Priddy) I do this for my small tiles and they stay flat.

 

Marcia

 

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Mrs. Christ am sorry I missed your question! The lumps and  discoloration are light effects from the photograph, and no, I didn’t mix  anything from the original terracotta clay. I bought this in an art supply store.

 Mrs. Judith more or less is what I do so your observation makes sense, I’ll test that also.

Mr. Pugaboo  when you  said “silica on the kiln  or  clay disks to raise them up off the shelf†what I understand you meant is to fire them on a flat surface or raise them in a way that the heat circulate all around them. Please enlighten me. Thanks

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A thin layer of silica on the kiln shelf acts like tiny ball bearings and allows the clay to expand and contract during firing without warping or cracking.

 

I use 1/4 thick bisqued clay disks in various sizes depending on the size needed. I place them under the piece and fire away. The disk raises the piece up enough to allow the heat to more evenly get around the piece and it also allows the pieces to move more easily in the kiln shelf without catching on its rougher surface. This is especially useful if you have old beat up shelves that are no longer smooth and even as the tiles try to follow the contour of the shelf.

 

Others here can probably tell you more about using silica (sand) on the shelf as I do not have only read here about it and seen it used in someone else's kiln.

 

Oh and by the way it's MS. Pugaboo. Lol still getting confused for a boy and my other name is no help either. Good luck with your project be sure to post pictures so we can all see how it ends up.

 

Terry

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Thanks Pugaboo, Now I know about the silica. This next Saturday I’ll fire my first sheet and of course I’ll comment and  post a picture. I have a few sheets and they will be ready for the kiln every two days. Every one of them has a new suggestion that I learned from you guys. Let’s see how they show. When  I have a good one this will be the master for the serial production. I need at least 40 of them in good shape to start my experimentation.  Thank you again 

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Here we have the result of your experience. Excellent results! The drying , perfectly straight and flat no cracks and hard enough to be handled.   The firing, perfect also,  excellent using a 06 cone. Here are the pics so you can judge it yourself also. I am very grateful  to all of you for your unconditional help. I learned from every one of you something that took me to this result.  I know that I’ll be back to the forum  because I want to experiment with different type of clay recipes to obtain the best porous clay for the project. Thanks

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