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macdoodle

cookies and porcelain issues

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I had cone 10 fired pieces have iron from cookies flash on bottoms if that is correct term. I'm getting it off but it is not easy or fast.

 

would those cookies, if they are slipped with an alumina added to a porcelain slip ( 1. pre fired first or 2. slipped at the cone 10 firing) work or do i need to make pure porcelain cookies for the next pieces?

 

I also had a piece since I'm doing thin and thick areas with and without added color - begin to crack in bisque I let the items dry slow over several weeks but loading is done by students who are not always so careful.

 

Does anyone have ideas how I can I save it before clear glaze and cone 10 firing?

Would paper clay work but be a different color? should i slip over and re-bisque if i use that?

 

Since i read that wadding is used wet in high fire

could small bits of thin porcelain be added like glue without risk or would the difference in shrinkage of wet and bisqued make that "glue" just sit alone as it shrinks more ?

 

-or is it best to fire and fix later using some sort of restoration technique I've seen but not yet found instructions on?

 

I am going to add alternate materials on at least one piece (after fire) but i would like to do that where I want to more than where I have to.

 

Also how thin does porcelain typically have to be to have good transparency? These 4 items are about color and some texture so I haven't tried going for transparency yet, but want to before I finish off this batch of Babu Porcelain.

 

 

Any ideas are greatly appreciated!

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also is there a way to tell the difference between cracks etc that are my errors in drying or other and kiln issues? i read about certain types of cracks and it seems that there might be a way to tell? where/when the problem began, but the info wasn't specific.

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Guest JBaymore

also is there a way to tell the difference between cracks etc that are my errors in drying or other and kiln issues? i read about certain types of cracks and it seems that there might be a way to tell? where/when the problem began, but the info wasn't specific.

 

 

 

One of the "must have" books for a ceramist is Hammar and Hammar's "The Potter's Dictionary of Materials and Techniques".

 

In that book is a section under the term "cracks". It is the definitive collection of answers to this exact question. Check it out.

 

best,

 

..............john

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also is there a way to tell the difference between cracks etc that are my errors in drying or other and kiln issues? i read about certain types of cracks and it seems that there might be a way to tell? where/when the problem began, but the info wasn't specific.

 

 

 

One of the "must have" books for a ceramist is Hammar and Hammar's "The Potter's Dictionary of Materials and Techniques".

 

In that book is a section under the term "cracks". It is the definitive collection of answers to this exact question. Check it out.

 

best,

 

..............john

 

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I add a little alumina to my wax resist for porcelain. It helps avoid fusing on the feet to the shelves or on flanges.

I would think it would help with the cookie problem as well.

 

As for transparency it would depend on the porcelain...if it will go translucent or not. Not all porcelains will be translucent.

I have used Southern Ice and in places it is translucent where thin..1/16-1/32".

 

Marcia

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Thanks! I wipe, not wax, bottoms, so maybe i need to change that for the porcelain. I currently have some babu (laguna) i heard southern ice is no longer available in US sometime back, but maybe i'll check into it again too!

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Thanks! I wipe, not wax, bottoms, so maybe i need to change that for the porcelain. I currently have some babu (laguna) i heard southern ice is no longer available in US sometime back, but maybe i'll check into it again too!

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You may want to take a look at Lakside Pottery's Ceramic repair and restoration lessons and tutorials listed in the page below. The information is with lots of illustrations and a video covering several aspects of repairing and restoring ceramic, china, porcelain and pottery:

 

http://lakesidepotte...-tutorials.html

 

Kindly, Patty and Morty

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If you're making pieces that are not even in thickness, porcelain is about the worst choice of clay bodies for that. Switch to a groggier stoneware if you want it to survive without cracking. Your cracking was likely not the result of someone loading the kiln, unless a piece was broken off, but rather due to construction technique. Slow drying does not always prevent cracking. Plus sometimes hairline cracks aren't visible until after the bisque.

 

Slip will not adhere to bisque, and just trying to fill the crack with slip will likely not work well. Paper clay may do the trick. As long as it's made from the same clay body, it will match in color. Patching after firing may be the easiest way to go, though.

 

Babu is wonderful stuff, but necessarily good for sculpture.

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