Pitterpotter Posted July 20, 2012 Report Share Posted July 20, 2012 I'm trying to work on reducing warpage in my pottery. I tend to have a problem with my slab built plates platters and bowls. Sometimes they come out perfect but alot of times they don't. I have a smaller slab roller and a pug that I pug out about a 3 or 4" round piece of clay, I think 'cut' it in half lengthwise and roll out the two halfs together layig them side by side on my board ad pressing them together but running them thru the roller. I'll then take each sectio and lay them out on my canvas with a bit overlapping and join them together using a rolling pin. Can anyone tell me 1# why I'm getting so much warpage and 2# what can I potentially adjust to prevent/reduce future warpage? Thank you in advance!! Debi Link to comment Share on other sites More sharing options...
Chris Campbell Posted July 20, 2012 Report Share Posted July 20, 2012 If I understand correctly ... You cut a pug in half lengthwise then lay them side by side lengthwise to feed through the slab roller? If this is right then you might get warping because the clay is always being stretched in one direction ... A possible solution would be to feed the cut pieces through across rather than with the rollers or roll across the top of the finished slab to even it out before using. I also loosen my slabs then let them rest a bit before I use them ... You'd be surprised how much they shrink back in just five minutes or so. Link to comment Share on other sites More sharing options...
Nelly Posted July 20, 2012 Report Share Posted July 20, 2012 I'm trying to work on reducing warpage in my pottery. I tend to have a problem with my slab built plates platters and bowls. Sometimes they come out perfect but alot of times they don't. I have a smaller slab roller and a pug that I pug out about a 3 or 4" round piece of clay, I think 'cut' it in half lengthwise and roll out the two halfs together layig them side by side on my board ad pressing them together but running them thru the roller. I'll then take each sectio and lay them out on my canvas with a bit overlapping and join them together using a rolling pin. Can anyone tell me 1# why I'm getting so much warpage and 2# what can I potentially adjust to prevent/reduce future warpage? Thank you in advance!! Debi Dear All, While I am no expert by any means, here is my off the top list of things that could be happening in my understanding of clay: 1. Clay body (may not be conducive to slab building depending on the size you are trying to create) 2. Smoothing the clay with a rib in different directions after you use the roller (something about aligning clay particles) 3. Clay memory if disturbed significantly in transfer from the slab roller to the board or mold 5. Sometimes the clay is not just not thick enough?? I have had clay split down the middle that is just not meant to make big projects. 6. Uneven drying (I used to roll up a newspaper and put it on top of my platters to get some of the water to go into the paper as it was drying. Boy was this wrong. Major warpage with this idea). 7. Drying too rapidly (I have done this numerous times and had major warpage even before the bisque firing) 8. Firing issues (uneven shelves) 9. Too much oil on my mold (cracks) These are off the top of my head ideas. If anyone wants to knock any of these down or cross them off the list feel free. As I said, I have just got my own studio so I would be interested in others comments. I have found in working with clay slabs that having them "set-up" tends to be better (i.e., giving them time to rest between the slab roller and my actual creating of the form). Sometimes I sandwhich the clay between two boards to keep them flat at this stage to get them ready to work with. They become just a little stiffer making it easier to work with (i.e., just before leather hard). Again, anyone with more experience feel free to say "Nelly is wrong" here as I am not an expert. I just know what I do with my slabs and what has/hasn't worked for me through trial and error. Nelly Link to comment Share on other sites More sharing options...
Pitterpotter Posted July 20, 2012 Author Report Share Posted July 20, 2012 If I understand correctly ... You cut a pug in half lengthwise then lay them side by side lengthwise to feed through the slab roller? If this is right then you might get warping because the clay is always being stretched in one direction ... A possible solution would be to feed the cut pieces through across rather than with the rollers or roll across the top of the finished slab to even it out before using. I also loosen my slabs then let them rest a bit before I use them ... You'd be surprised how much they shrink back in just five minutes or so. You are correct, after cuttig the pug in half I'll lay the pieces side by side lengthwise (overlapping slightly ad 'smushing' together) the running them thru the roller. I do use the rolling pin to roll over the completed pieced together slab to make sure its as even and smooth as I can get. I also use a wet sponge to smooth out the surface and then after I have my slab cut to size of the mold I'm using I'll put the smoothed side down and repeat that wet sponge process on the other side to ensure my seams are bonded. I will try letting it rest as I normally go right to working with it, and thank you for your input, its greatly appreciated! Debi Link to comment Share on other sites More sharing options...
Pitterpotter Posted July 20, 2012 Author Report Share Posted July 20, 2012 I'm trying to work on reducing warpage in my pottery. I tend to have a problem with my slab built plates platters and bowls. Sometimes they come out perfect but alot of times they don't. I have a smaller slab roller and a pug that I pug out about a 3 or 4" round piece of clay, I think 'cut' it in half lengthwise and roll out the two halfs together layig them side by side on my board ad pressing them together but running them thru the roller. I'll then take each sectio and lay them out on my canvas with a bit overlapping and join them together using a rolling pin. Can anyone tell me 1# why I'm getting so much warpage and 2# what can I potentially adjust to prevent/reduce future warpage? Thank you in advance!! Debi Dear All, While I am no expert by any means, here is my off the top list of things that could be happening in my understanding of clay: 1. Clay body (may not be conducive to slab building depending on the size you are trying to create) 2. Smoothing the clay with a rib in different directions after you use the roller (something about aligning clay particles) 3. Clay memory if disturbed significantly in transfer from the slab roller to the board or mold 5. Sometimes the clay is not just not thick enough?? I have had clay split down the middle that is just not meant to make big projects. 6. Uneven drying (I used to roll up a newspaper and put it on top of my platters to get some of the water to go into the paper as it was drying. Boy was this wrong. Major warpage with this idea). 7. Drying too rapidly (I have done this numerous times and had major warpage even before the bisque firing) 8. Firing issues (uneven shelves) 9. Too much oil on my mold (cracks) These are off the top of my head ideas. If anyone wants to knock any of these down or cross them off the list feel free. As I said, I have just got my own studio so I would be interested in others comments. I have found in working with clay slabs that having them "set-up" tends to be better (i.e., giving them time to rest between the slab roller and my actual creating of the form). Sometimes I sandwhich the clay between two boards to keep them flat at this stage to get them ready to work with. They become just a little stiffer making it easier to work with (i.e., just before leather hard). Again, anyone with more experience feel free to say "Nelly is wrong" here as I am not an expert. I just know what I do with my slabs and what has/hasn't worked for me through trial and error. Nelly Thanks Nelly, those are all good food for thought as well. I'm certainly not an expert myself having only been working with clay for a little over a year and basically all self taught. I see several 'items' on your list that I could evaluate in the way I handle my slabs and creations. I certainly appreciate your input as well! Thank you so much! Link to comment Share on other sites More sharing options...
Mark C. Posted July 20, 2012 Report Share Posted July 20, 2012 Can you use another clay body with more open tooth in it? That way it can take the torture better-warp less Mark Link to comment Share on other sites More sharing options...
Pitterpotter Posted July 20, 2012 Author Report Share Posted July 20, 2012 Can you use another clay body with more open tooth in it? That way it can take the torture better-warp less Mark Do you mean somethig with a higher grog content? Link to comment Share on other sites More sharing options...
Chris Campbell Posted July 21, 2012 Report Share Posted July 21, 2012 We are constantly at the beck and call of "clay memory". So think about it slab roller wise ... You have taken clay that was pugged out in one direction ... Compressed, stretched and rolled it FLAT in a direction ... Message to clay is that it better stay flat and with the grain! So can you take that clay and make a curve without getting grief? Take clay that has been given a pretty clear message to stay flat and expect it to form a bowl? I think you have to be using a very forgiving clay body to expect this .... Lots of grog and easy going or use another method of getting a slab of clay. Link to comment Share on other sites More sharing options...
Mark C. Posted July 21, 2012 Report Share Posted July 21, 2012 Grog or sand both are toothier bodies. We press slabs into molds here a fair amount (cone 10 ) and use a special body that does not care what happens to it. My regular porcelain cracks and warps too much for this. I am not to keen on cone 6 or low fire bodies . What I do know is they sometimes do not throw as well (especially low fire 06). Tight talc 06 bodies do not work well for slab draping. Ask your supplier about better body for this. Mark Link to comment Share on other sites More sharing options...
Pitterpotter Posted July 21, 2012 Author Report Share Posted July 21, 2012 Grog or sand both are toothier bodies. We press slabs into molds here a fair amount (cone 10 ) and use a special body that does not care what happens to it. My regular porcelain cracks and warps too much for this. I am not to keen on cone 6 or low fire bodies . What I do know is they sometimes do not throw as well (especially low fire 06). Tight talc 06 bodies do not work well for slab draping. Ask your supplier about better body for this. Mark I will do that but couldn't I just add some grog or sand to what I have. Is that a possible solution? Link to comment Share on other sites More sharing options...
Mark C. Posted July 21, 2012 Report Share Posted July 21, 2012 Yes you can try that but its an experiment -so keep this in mind and test it first before producing work thats got a lot of work in it. My time is worth more to me than wedging grog but everyone has a different take on this.What temperature range is this clay?? Mark Link to comment Share on other sites More sharing options...
Pitterpotter Posted July 21, 2012 Author Report Share Posted July 21, 2012 Yes you can try that but its an experiment -so keep this in mind and test it first before producing work thats got a lot of work in it. My time is worth more to me than wedging grog but everyone has a different take on this.What tempiture range is this clay?? Mark Its a high fire clay (says 6-10) and I would run a batch thru the pug to test and see how it works. Link to comment Share on other sites More sharing options...
Ben Posted July 24, 2012 Report Share Posted July 24, 2012 Yes you can try that but its an experiment -so keep this in mind and test it first before producing work thats got a lot of work in it. My time is worth more to me than wedging grog but everyone has a different take on this.What tempiture range is this clay?? Mark Its a high fire clay (says 6-10) and I would run a batch thru the pug to test and see how it works. Adding grog can have effects on the vitrification and the coefficient of expansion of the clay body. The final fired absorption % could change as could the COE. Testing would be a must as you may have glaze fit problems. Link to comment Share on other sites More sharing options...
lakesidepottery Posted July 25, 2012 Report Share Posted July 25, 2012 These two tips pages from Lakeside Pottery might answer your questions: Making Large Slab Constraction - Step-by-step: http://lakesidepottery.com/Pages/Pottery-tips/How-to-make-large-slab-form.htm Making Ceramic Flat forms: http://lakesidepottery.com/HTML%20Text/Tips/Making%20Ceramic%20Tiles.htm Kindly, Patty and Morty Link to comment Share on other sites More sharing options...
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