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jammy43

How To Slab A Round Cylinder

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wondering what method you use to create round cylinders from slabs.  The few attempts i've made is to let my slab dry to a soft leather-hard and then just prepare and set  the ends together - but I don't get a perfect (or close too) circular cylinder - its always way wonky.

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I'll use any cylindrical form, from the cardboard roll from toilet paper to a large oatmeal container. Just remember to wrap a layer of newspaper around the form before the clay. When the clay firms up, slip the roll out. 

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I form my slabs around cardboard tubes/pvc pipe/etc. to make cylinders. The tubes/pipes/etc. are covered with a nylon knee high stocking to prevent the clay from sticking to the form; others use newspaper to wrap the form, but the stockings can be reused vs. newsprint that gets wet and sticks to the inside of the cylinder. The joining edges of my slabs are beveled to 60 degree cuts -- not 45 degrees. I prefer the wider surface for joining, plus it makes for a stronger join since more surface area is involved.

 

To keep forms round during drying, I do two things. First, before wrapping the slab on the form, I place it inside facing up on a piece of foam and roll the cylinder or a rolling pin on the slab to give if a new, round memory (as opposed to being a flat slab). Then I wrap it on the form. After wrapping on the form, I take either wide strips cut from the plastic bags newspapers are delivered in, or newsprint, and wrap them around the clay slab on the form to reinforce the new memory. They stay on even after I remove the cardboard/pvc/etc form until the form is at least cheddar chees leatherhard -- by that time, the strips will fall down due to shrinkage.

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Over the years, I have used any round form I could find, as long as it did not have ridges and other things to  catch on the cylinder. Always would wrap with newspaper to allow easy release. Sometimes if the cylinder was large, I would join on the inside of the cylinder and then just let it get leather hard and the shrinkage would release it.

 

Finally for forms that were round in circumference , but where the form was a little bowed or other wise on the vertical, I would make the piece in two slabs, top and bottom. Slip each off individually, and then join together when leather hard.

 

Learning to work with forms while handbuilding is a big part of the process.

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I wrap slabs around large sonar (sp) tubes or PVC pipe from Home depot.I use a cardboard tube, wrap it with newsprint. Then roll a precut slab on tar paper around the tube. Tape with duct tape. slide the tube out, work on the seam, and let the clay set up.This photo is from my Architectural Ceramics workshop in Italy at La Meridiana in 2004.The paper keeps the clay from sticking to the tube.

Marciapost-1954-0-39247100-1418312261_thumb.jpg

post-1954-0-39247100-1418312261_thumb.jpg

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any smooth-sided cylindrical form on the inside (cardboard tube from paper, sonotube for casting cement, PVC, ABS, anything...)

roll out slab with machine or make by hand, put layer of newspaper between clay and form to prevent sticking and to aide in slipping it out.  cut a straight edge on slab, then roll it over form (like how you pickup up dough with rolling pin) to make slight impression where the seam will be - then cut both ends at a 45* angle so you get a nice flat seam with most surface area for good contact.

the tip Marcia gave regarding cradling the slab with tar paper is a good one - great for when you cannot roll the tube over the slab and need to apply it to a vertical form.

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