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Joseph F

Quick Question: Sea Shells - Cone 6 - Which Type?

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Joseph F    865

Update: I fired some more sea shell stuff on some test tiles again. (working on my base glaze for most of my work and I wanted to see its reaction to shells as well:

 

Sea Shell Flash

 

This is the same tile in the picture: right side was placed on the shell the left side was up. The result is fantastic. Almost a 100% difference in color, and the area of the flash was rather large considering it was only touching on those three little spots. This is promising for when I side fire cups this way. 

 

I had no idea that I could get this much color variety from the shells as well as the texture. I just wanted to post this here as a follow up. Pretty happy with these results. The glaze seems to make a difference. These were the same shells that my son had picked up from our vacation 2 years ago. They have just been sitting in a plastic bag not sealed up. I am excited to get fresh ones this summer and side fire almost all my work. Now I just have to figure out how to make wadding to place the shells on top of so that cups don't fall off the shells.

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Joseph F    865

I have a new question regarding this stuff. I am going to the beach soon and I am going to come home with a bucket of shells and start firing my work on its side. I have been looking at pictures of people who fire on shells and they use wadding under the shell to make sure the pot doesn't fall over. This makes a lot of sense. Is there a certain type of wadding I should use for cone 6? 

 

I know above John said that his student used 50% plaster and 50% whiting, however that was directly on the pot for those marks if I understood correctly. So I want to use shells instead of making my wadding look like shells.

 

 

Does anyone have a good recipe for cone 6 or can guide me to a place I can read about it? Or should I just use a high fire wadding recipe and not worry about it? 

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Joseph,
 
At school we use wadding made a 50/50 volume mix of alumina hydrate and EPK.  When I can't find wadding I just use recycled cone 10 clay and add dry clay to it to make it nearly dry; then punch lots of needle tool holes in the mix after I stuff it in the shells.  It is also a good idea to put a daub of Elmer's glue in the shell to keep the wadding in place while handling everything.  The wadding shrinks a bit and sometimes gets separated from its shell. 
 
Some wadding recipes add an equal volume amount of sawdust to the mix to make it more open and drying.  The wood dust also contributes a little 'local color' to nearby work  -- sometimes.
 
If you are firing to cone 5 in electric kiln, I suspect a mix of sand and epk would work fine inside the shells. 
 
lt

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Joseph F    865

 

If you are firing to cone 5 in electric kiln, I suspect a mix of sand and epk would work fine inside the shells. =

 

I am firing to cone 6. Sand and EPK sounds interesting. Just try to mix it up until its sorta tacky and shove it into the shells and poke holes then let it dry?

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Joseph F    865

yep

 

Thanks a ton! Going to try it very soon. Got my 2 gallon bucket with a lid ready for a massive amount of shells.

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JBaymore    1,432

Simply pack the shell with wadding.  Some situations call for a "cookie" type base under the shells to stabilize it all. 

 

50/50 alumina hydrate and any kaolin is the "bulletproof" wadding mix.  But a bit expensive due to the alumina price.  Some folks use a 50/50 fireclay and silica sand blend.  (If you use sand.... make sure it is silica sand.)  Some use fireclay and as much sawdust as the mix can hold and still be formable.

 

At cone 6 you have a lot more "latitude" than those of us firing hotter and longer in a wood kiln.

 

best,

 

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

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Joseph F    865

Simply pack the shell with wadding.  Some situations call for a "cookie" type base under the shells to stabilize it all. 

 

50/50 alumina hydrate and any kaolin is the "bulletproof" wadding mix.  But a bit expensive due to the alumina price.  Some folks use a 50/50 fireclay and silica sand blend.  (If you use sand.... make sure it is silica sand.)  Some use fireclay and as much sawdust as the mix can hold and still be formable.

 

At cone 6 you have a lot more "latitude" than those of us firing hotter and longer in a wood kiln.

 

best,

 

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

 

Thanks John! I assume sawdust would be an error in an electric kiln since it would burn and smoke? I think I will just go with the 50/50 alumina hydrate and kaolin. 

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Found this: http://www.pottery-magic.com/pottery/clay/low-shrink.htm

 

There are pottery clay bodies that can be made that have almost no shrinkage.
It is made from a large amount of talc mixed with a small percentage of standard clay.
The result of this mixture is not all clay, it will act like plastic clay to a certain extent and can be worked in much the same way.
Talc is magnesium silicate and when mixed with water has many of the properties of clay, but with little or no shrinkage.
It is also highly resistant to thermal shock and can be fired in minutes instead of the usual hours.

When mixing a low shrink body, you can use up to 90 percent talc.
If you use any more than this, the body will lose its workability and firing strength.
With the addition of 10 percent standard clay, the necessary chemistry for firing is retained.
Low shrink clay should only be fired at low temperatures because talc loses its density at 2110Ëš F or 1100Ëš C and will collapse.
When fired to a temperature of about 1900Ëš F or 1040Ëš C the clay will fuse and be almost as dense as porcelain.
When talc is used in small amounts in clay, the talc acts as a refractory ingredient, giving good resistance to heat and thermal shock and making it and ideal addition to ovenware pottery.

Clay with talc added are mainly used for commercial tile manufacturing because the clay can easily be rolled or pressed, will shrink little or not at all and will not warp when drying or firing.
Talc is also much cheaper than clay and its low expansion rate makes for a good craze free glaze fit. 

 

IDK, but maybe with no shrinkage you could get the results you are looking for. 

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