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Is Cone 6 Practical For Domestic Ware In The Uk?


PottaFella

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Not a great situation if the manufacturer's guidelines are imprecise. I would happily fire lower if I could be sure which products were actually going to vitrify (even though that starts off a whole new chase for glazes!). Because of my relative inexperience I have only tested a limited range of samples so far. Very interested to hear anyone's test results.

Joe

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I should add in an extra complication to this... matt glazes.

 

Just speaking with a glaze supplier today and they reminded me that matt glazes also cannot be relied upon to be watertight, so add together a stoneware body that may not have vitrified (at cone 6 or so) with a matt glaze that is slightly porous and you haven't got the greatest of recipes for a watertight jug!

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I should add in an extra complication to this... matt glazes.

 

Just speaking with a glaze supplier today and they reminded me that matt glazes also cannot be relied upon to be watertight, so add together a stoneware body that may not have vitrified (at cone 6 or so) with a matt glaze that is slightly porous and you haven't got the greatest of recipes for a watertight jug!

 

Ummm, misinformation there. For functional stoneware or porcelain pots the clay should not leak even with no glaze. Good way to test for that is to make some flat bottom pots, no glaze inside or out, fire them to whatever cone you will be firing real pots. Fill them with water and set them on a sheet of newsprint. Leave them alone for a week, any wrinkles in the paper and the clay leaks. Glossy glaze, matte glaze or anywhere in between, it can't be relied upon to make a clay watertight. (I learned that the hard way)

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  • 1 month later...

Oly - if you give Valentines a ring they're always very happy to advise. Similarly Potclays and Potterycrafts. I'm just firing some stoneware B17C to 1200oC with a 30 minute soak. I don't usually use stoneware, this was from a throwing weekend I attended a few months back. Hopefully they'll survive AND be leakproof as there are some mugs and a vase in there. Having read your post I'll definitely do a leak test before using any of them!

 

 

 

Having had some problems with vessels leaking due to clay not being fully matured at cone 6 (and glazes crazing), I'm beginning to wonder if this cone 6 thing, which I thought was such good idea when I first got my kiln and wanted to save energy, well, maybe it just isn't really that practical in the UK, where I believe the tradition has been of high-fired stoneware cone 10+.

 

It seems in the USA there may be a better selection of clay bodies developed for lower temperatures and hence cone 6 in electric kilns is the way it's done.

 

Be very interested to hear views on this from both UK and USA potters.

 

If you're talking about the ES5 clay (as in another topic recently) I don't understand why you're having trouble with it, I use it regularly, and I discovered recently that a couple of my friends are using it at a class they take, the class is run by Colin Jones who was head of ceramics at Brockenhurst college, he supplies and fires their pots, none of us have any problems with ES5 not being watertight @ ^6.

 

Another topic I dug out appears to bear this out:- http://community.ceramicartsdaily.org/topic/14544-stoneware-cone-67-pot-weeps-slight-amount-water/page-2

 

I'd be quite happy to write out my firing schedule for both bisque and glaze if you're interested, and I can give you a clear glaze recipe which works fine for me on ES5.  I think it would be better than Michael Bailey's T14, which on checking his book seems to be more suited to using with oxides which provide some fluxing to the glaze  (read p32 ) rather than as a clear liner glaze.

 

 

 

Celia did you have any luck with testing the B17C?

 

Ayjay have you done any formal tests for absorption and leakage on the ES5 you mentioned?

 

Joe

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Oly - if you give Valentines a ring they're always very happy to advise. Similarly Potclays and Potterycrafts. I'm just firing some stoneware B17C to 1200oC with a 30 minute soak. I don't usually use stoneware, this was from a throwing weekend I attended a few months back. Hopefully they'll survive AND be leakproof as there are some mugs and a vase in there. Having read your post I'll definitely do a leak test before using any of them!

 

 

 

Having had some problems with vessels leaking due to clay not being fully matured at cone 6 (and glazes crazing), I'm beginning to wonder if this cone 6 thing, which I thought was such good idea when I first got my kiln and wanted to save energy, well, maybe it just isn't really that practical in the UK, where I believe the tradition has been of high-fired stoneware cone 10+.

 

It seems in the USA there may be a better selection of clay bodies developed for lower temperatures and hence cone 6 in electric kilns is the way it's done.

 

Be very interested to hear views on this from both UK and USA potters.

 

If you're talking about the ES5 clay (as in another topic recently) I don't understand why you're having trouble with it, I use it regularly, and I discovered recently that a couple of my friends are using it at a class they take, the class is run by Colin Jones who was head of ceramics at Brockenhurst college, he supplies and fires their pots, none of us have any problems with ES5 not being watertight @ ^6.

 

Another topic I dug out appears to bear this out:- http://community.ceramicartsdaily.org/topic/14544-stoneware-cone-67-pot-weeps-slight-amount-water/page-2

 

I'd be quite happy to write out my firing schedule for both bisque and glaze if you're interested, and I can give you a clear glaze recipe which works fine for me on ES5.  I think it would be better than Michael Bailey's T14, which on checking his book seems to be more suited to using with oxides which provide some fluxing to the glaze  (read p32 ) rather than as a clear liner glaze.

 

 

 

Celia did you have any luck with testing the B17C?

 

Ayjay have you done any formal tests for absorption and leakage on the ES5 you mentioned?

 

Joe

 

 

 

Nothing formal Joe: I tested some a couple of years ago following a procedure that I found on this forum somewhere and the results were well within the range I was hoping for.

 

It was either 1.2 or 1.6, I can't remember which, (I should probably make another test)

 

From what I make and use at home, viz. a variety of ever changing mugs (my wife is an expert at breaking things) are the most likely to cause a noticeable problem: they don't.

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  • 5 months later...

I have the same problem with UK suppliers - none of them have tested at cone 6 and seem completely surprised when I ask them about it.  I've tested a few bodies and can say that B17C does not work at cone 6.  It's brittle and leaks.

 

What does work for me is Valentines Stoneware toasted.  Which is a darker buff clay that happens to be super cheap.  I'd like to try KGM, but my local supplier doesn't sell it and I don't want to order a whole pallet from valentines.  

Any info people can share about one 6 in the UK greatly appreciated.  I'd try ES5 but it's really expensive.

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I've used Toasted Stoneware in the past and quite like it. Have you done any seepage, absorption or warp tests on it at ^6?  It did some tests but then realised my kiln was overfiring to ^8  - at that temp it has barely measurable absorption and by ^9 there is slight but noticeable warping. Would be interested how absorbant it is at a real ^6.

 

Thanks for the heads-up about B17C. I've just bought some V9a to test.

 

(I'm currently using ES10 now which is a smoother ES5).

 

Joe

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