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Clay and glaze


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Sorta beginner potter here! I recently came across some glaze I really wanted to try out! On the pint it says “apply to cone 04 bisque” but it fires to ^6...wouldn’t that melt my pottery into a puddle if my 04 earthenware clay was fired to ^6? Or is it referring to stoneware? What type of clay is best for ^6? Thanks in advance! 

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7 hours ago, Lalablue said:

hat type of clay is best for ^6? Thanks in advance! 

Cone six rated clay. Often called midfire clay. Comes in stoneware, porcelain, etc..... cone six clay vitrifies at cone six meaning it is fully fired at cone six and not over or underfired. The geology of the earth is about cone ten so in order to make things melt earlier we add things to clay and glazes to make them melt at cone six and actually add more things to make them melt at 04 or lowfire as some say.

Earthenware tends to be more in the lowfire range but in general is not as sturdy as mid and high fire and usually not waterproof even fully fired to its cone rating.

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when you match the final clay temperature to the final glaze temperature, everything works well.   if you intend to make earthenware, there are facts about it that bill mentions above and that you can research in quality written books or articles in magazines and a little online info. 

if you want to make items that will be sturdier and that will give you more options, cone 6 stoneware clay and glazes are very widely used these days.    just like everything else, ceramics goes through phases of popularity.   right now and for many years, cone 6 is more popular with potters because it is so much easier to use electricity to fire the work.  that makes it available to many more people than the previously popular cone 10 clay and glazes that were fired by burning either wood or gas in a (usually) much larger kiln.   

today, having a large gas or wood burning kiln is available to potters who have the room and the local regulations that allow their use in their area.   when i started, 1972, almost everything i could find about firing assumed that cone 10 was what everyone did.  and that anyone who used earthenware was only a hobby potter who liked to "play" in clay.

do some research on pottery.   do not think that books or articles written long ago are useless to you, working with clay has been done for so many centuries that anything you find will be interesting, even if it does not apply to your work today.

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Do you have a library in your area?   I have been working with clay since 1966 and one trip I looked forward to every month was our family trip to the library.   I would scour the shelves for any new books on clay, sculpture and potters.   My son would search the children's shelves  and my husband liked the technical and mechanical books.  We would meet up in the children's room after a hour and rent a painting to hang in our living room before we headed  home.  Start out with a basic general knowledge book and work your way up,  you need a good solid  base of knowledge to become a good potter.     Denice

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3 hours ago, Bill Kielb said:

The geology of the earth is about cone ten so in order to make things melt earlier we add things to clay and glazes to make them melt at cone six and actually add more things to make them melt at 04 or lowfire as some say.

Except for naturally  occurring earthenware which has been dug from the ground and used as is in many parts of the world for thousands of years.

Edited by Min
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I dislike making such broad generalizations about the functional suitability of a piece being based on the cone it was fired to alone. Earthenware glazed all over with a glaze that fits properly is more durable than a refractory porcelain that’s still porous at cone 9 with a crazed traditional celadon glaze on it. You can still use the celadon piece, but it might weep, and it probably won’t hold up over time the same way a well made earthenware piece will. 

When you’re looking to make functional items, making sure your glaze is meant to mature at the same point your clay does, making sure the glaze works with your clay body properly and making sure that both clay and glaze are properly mature will help you make more durable work. It’ll lessen the possibility of a wide variety of ways to mess up your work, and lord knows there’s a lot of those!

If you’re not making functional work, you have a lot more room to fudge things.

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