Glaze Compatibilities

[reen]

I have cone o6 and cone 6 glazes.Can I use these two glazes together on one piece and then fire to cone 6. If not why, what would be the results? Can I fire pieces together with o6 glaze on some and 6 glaze on some, then firing to cone 6. If not what might be the results.Can I use cone 6 glaze on low fire earhenware clay. I am very new at this, all comments and patience would be thankful.

[Marcia Selsor]

The temperatures are very far apart. First fire the Cone 6 (2200F) glazes which is the hotter temperature. Then fire the 06 ( about 1825F) at the lower temperature. If you fire the lower temperature first , when you fire the higher temperature the low fire glaze can run or burn. Here is a link to a temperature chart.

 

http://www.bigceramicstore.com/info/ceramics/cone-chart.html

 

Marcia

[bciskepottery]

Your glazes are formulated to melt at different temperatures. But, with testing, that doesn't mean you could not layer the cone 06 over the cone 6 and fire to cone 6. The 06 glaze will likely become very runny. Start with some test tiles and see just how runny the 06 glaze becomes when fired to cone 6. Do some tiles just 06, some with 06 over 6. Put the test tiles in a glaze tray to trap any overmelts that could run onto your kiln shelf.

 

When you add two glazes together, whether the same cone or different cones, you end up creating a third glaze. That glaze may or may not be suitable for functional ware. A stable glaze when added to another may result in a not-so stable glaze for food surface purposes. So, be mindful of that, too.

 

Fong Choo creates his glazes by mixing low and high fire glazes for the exteriors of his teapots. But, he tests the heck out of the combinations to find the right look and result before committing to a teapot.

[Nancy S.]

What you're thinking about also depends on your clay! If you have low-fire clay (cone 05-06) and you try to fire it to cone 6, no matter what glazes you're using, your clay will melt into a blob on the shelf.

 

Since you're new at this, stick to whatever glaze is made to work with your clay and keep them separate.

[Norm Stuart]

Personally I don't understand the purpose of low-fire ^04 clay.  When fired to maturity my understanding and experience is it's no stronger than Cone 6 clay fired to bisque.

 

Do people buy low-fire high-talc clay for economy reasons?  What purpose does it serve?

 

 

What you're thinking about also depends on your clay! If you have low-fire clay (cone 05-06) and you try to fire it to cone 6, no matter what glazes you're using, your clay will melt into a blob on the shelf.

 

Since you're new at this, stick to whatever glaze is made to work with your clay and keep them separate.

[bciskepottery]

What you're thinking about also depends on your clay! If you have low-fire clay (cone 05-06) and you try to fire it to cone 6, no matter what glazes you're using, your clay will melt into a blob on the shelf.

That may not be true for all earthen-ware clays; as a test, I've fired Standard 104 w/Grog test tiles to Cone 6 with no issues (or melting). Some clays will melt, but not all. I have seen the unfortunate results (melted blog) of a Con 6 clay fired to Cone 10; it was supposed to be a pair of mugs; but the person making them used two different clay bodies and ended up with one mug melting into the other.

[bciskepottery]

Personally I don't understand the purpose of low-fire ^04 clay.  When fired to maturity my understanding and experience is it's no stronger than Cone 6 clay fired to bisque.

 

Do people buy low-fire high-talc clay for economy reasons?  What purpose does it serve?

Purpose ties to functionality and the qualities of particular clay bodies for different types of things. We recently had a threat on the yonggi (sp) jars from Korea, and how those jars were especially useful for fermentation of kimshi, sauces, and other foods. That fermentation was tied to the porousness of the earthenware clay used to make the jars. When they tried that with more vitrified clays, the results were not the same. Similarly, the yinxing clays used for teapots are prized for their quality of being able to absorb the flavors of teas -- again because of the porosity. An earthenware wine chiller probably keeps cooler than one of a higher fired clay. Eartheware vessels seems to be a favorite for storing water due to its insulating properties.

 

I don't think its a matter of economy; earthenware and stoneware seem to be similarly priced. There are economies due to lower firing temperatures, especially if you use an electric kiln. But I think the real purpose goes back to the functionality desired. And for some purposes, earthenware is preferable to other clay bodies.

[Norm Stuart]

For some reason schools, primarily, purchase low-fire Cone 04/05 clay which is not even as durable as Cone 6 Clay when both are bisqued to Cone 04, then glazed and fired to Cone 06.

 

If you know that school curricula now require learning how to make Kimchi jars or porous tea pots, that is indeed the answer.

 

I think the most likely answer is there was a good reason for this 50 years ago when manufactured Cone 6 clays did not exist, so Cone 05 talc clay bodied filled a niche.  Yet many ceramic programs continue purchasing Cone 05 clay, when Cone 6 clay bisqued to the same cone would do just as well - without having to worry about the clay body melting all over the inside of the kiln or concerns about using both high fire and low fire glazes.

 

Personally I don't understand the purpose of low-fire ^04 clay.  When fired to maturity my understanding and experience is it's no stronger than Cone 6 clay fired to bisque.
 
Do people buy low-fire high-talc clay for economy reasons?  What purpose does it serve?

Purpose ties to functionality and the qualities of particular clay bodies for different types of things. We recently had a threat on the yonggi (sp) jars from Korea, and how those jars were especially useful for fermentation of kimshi, sauces, and other foods. That fermentation was tied to the porousness of the earthenware clay used to make the jars. When they tried that with more vitrified clays, the results were not the same. Similarly, the yinxing clays used for teapots are prized for their quality of being able to absorb the flavors of teas -- again because of the porosity. An earthenware wine chiller probably keeps cooler than one of a higher fired clay. Eartheware vessels seems to be a favorite for storing water due to its insulating properties.

I don't think its a matter of economy; earthenware and stoneware seem to be similarly priced. There are economies due to lower firing temperatures, especially if you use an electric kiln. But I think the real purpose goes back to the functionality desired. And for some purposes, earthenware is preferable to other clay bodies.

 

[bciskepottery]

With apologies to Reen, the original poster; it seems we have strayed from the original question of using cone 06 and cone 6 glazes and firing to cone 6 to what is the purpose for low fire clay, etc. Hopefully the earlier part of this thread answered your question.