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Best Way To Sand Bottoms Of Warped Pottery/sculpture


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For reasons I don't understand, most of the 40 sculptures I've made in the past few months (that are headed for a craft show in less than a week!!) are warped.  I'll worry about the "why" later, but right now I need to figure out "how" to sand the bottoms to take out the slight warpage.  I have a belt sander that I can flip upside down; will that do the job with 80 grit belts?  Or is my booth gonna be full of rockin' sculptures???

 

Jayne

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I would try the belt sander-what cone is this work fire to-as thet will make a huge difference.

You couls also use those small clear silicone cabinets bumps on bottoms which will negate the uneveness.They sell them at hardware stores.

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Thanks, Mark. This is High water Raku clay fired to cone 5 (it has a firing range of 06-6). Today I bought some expensive "ceramic sanding belts“ which are supposed to be stronger and last longer. The"ceramic" has nothing to do with ceramics as we know it, just a stronger product. I've looked at local hardware stores and Michaels Crafts for those clear rubber bumpers but finally found them at Hobby Lobby. Maybe between 40 grit paper and bumpers, I'll make it to the show!

 

Any guesses as to why the work is suddenly warping? It has warped as low as cone 1 this time out.

 

Jayne

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Ive used Diamond blades on an angle grinder before. If you live next to a harbor freight you can get blades for cheaper than name brand at typical hardware store. Theyre not to bad and Ive gotten lots of use from them. Even angle grinders if you dont have one. I have 3 of the Chicago Electric 4 & 4 1/2 in ones and they last to my abuse on glass, metal, and rock. The only thing to take into account is making small short passes so you can etch away a little at a time without chipping. Im sure this goes without mentioning as well but slow and steady wins the race if water or oil is not involved to keep the temps down.

 

Also depending on how hard the clay actually is you could use a wire brush attachment.

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Warping comes from uneven contraction ( more likely ) and expansion, or a combination of both. Slow the drying process! What are you drying your pieces on? What is your firing schedule? Is it possible to compress clay on bottoms more?any chance you pieces a plucking? Have you tried firing work on a bit of sand?

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Mark, the sculptures did warp while drying, but I sanded the bottoms before bisquing until everything was perfect.  Then they came out of the kiln a mess!  I found that you're right about cone 5 -- it is a pain to sand, although I had some successes.

 

Thanks MMB for the mention of the Diamond blades.  I purchased my angle grinder from Harbor Freight - a favorite fun store where I find all kinds of great things for the studio.

 

Big Lou, it's possible that I'm not drying the work slowly enough.  I do dry them on a rack and I candle them for a long time (8-12 hours) before using the slow bisque setting on my kiln, and I frequently use sand.  I'll try compressing better the clay slabs that I use for bottoms. 

 

 And I don't know what "plucking" is!!

 

Jayne

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And I don't know what "plucking" is!!

 

Jayne

Plucking normally occurs with porcelain and/or very smooth, non-groggy porcelaneous stoneware clay bodies (e.g., B-Mix, Little Loafers). Basically, the foot fuses to the kiln shelf (even if waxed), generally small half-moon pieces/chips. A little alumina in the wax generally fixes the problem.

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So, THAT'S what that's called.

 

Yeah, I was totally gonna suggest diamond discs. I used to work in my uncle's metal shop some summers and he always used diamond discs in the radial saw I used to cut the steel rods with. :)

 

I dry my statues over the course of a month, lightly covered in plastic, and I seem to have little trouble with warping--even when I worked in ^10. :) Best of luck; how infuriating that must have been. :(

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