Is Cone 6 Practical For Domestic Ware In The Uk?

[PottaFella]

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.

[neilestrick]

You have to find a clay body that is formulated to mature and vitrify at cone 6. Anything rated to go higher than cone 6 is going to weep.

[glazenerd]

Not an expert, but from the posts I have seen from UK potters over time indicate that clay is rated on a broad firing range. If that is true, it would certainly play into the problem.

[High Bridge Pottery]

It is interesting, the clay sold as terracotta has a firing range up to 1220 but all stoneware goes up to 1260/1300.

 

I think you are probably right that clays sold as stoneware are cone10 clays even if their range goes from 1080-1280. That doesn't mean there is not one out there that would suit cone6 but I have never found much useful data about the clays out there.

 

I would try a terracotta rated to 1220 and see if you have any luck.

 

There is one here rated to 1120c but also says 'will vitrify at high stoneware temperatures' after having a look through valentines clay it looks like a few possible cone6 bodys could be filed under white earthenware/terracotta.

 

"KGM Body     can be fired 1080-1120oC

White to Off White at higher temperatures.

Smooth. Cost effective white earthenware clay which will vitrify at high stoneware temperatures. Due to very fine grog will give a light speckle at the highest te

 

"Potclays 1141 Studio White Earthenware (LT25)

White.

Smooth. Ivory white very plastic white clay for throwing.1100-1220oC"

 

Potclays actually give this clay a vitrification range of 1180-1250 but the firing range above. Who decides to put these things.

http://www.ctmpotterssupplies.co.uk/PotclaysTechnicalInformation.pdf

[MartinB]

Yeah I've seen very few cone 6 clay bodies that aren't sold as firing from cone 6-10.

 

Keep reading posts here about beautiful translucent cone 6 'Frost' porcelain but there's nowt in the uk.

[glazenerd]

Peter Frolich of Austria fires crystalline glazes on stoneware from Germany. He makes some rather intricate shapes when throwing, including a thrown egg. The mere fact that he can grow large crystals on stoneware is telling of the quality of the clay. He made some comments about the clay in Peter Issley's "Macro Crystalline Glazes"...

 

Nerd

 

Fuchs Cmpany - Westerwald Germany

Issley uses Potclays and Limoge

[Sputty]

.

[Roberta12]

Oly, I was in London about 3 years ago, and set up a visit with North Street Potters in Clapham.  They fire to cone 7 (if my memory serves me) and make functional ware for restaurants and cafe's.  Might be worth a call just to see where they get their clay.  Again, if I am remembering correctly, they were mixing their clay from dry mixes.  That would be very frustrating to never get vitrified work! The woman in charge was Naine. 

 

Roberta

[Marcia Selsor]

So you have to find the right clay that matures and adjust your glazes to not craze. I make functional ^6 in Ox. I use to make it in ^6 reduction from 1980-2000. You need to work on it.

Marcia

[Min]

I was curious about the lack of midrange rated clays over there so I did a little looking around online for some. In addition to the ones Joel and Sputty found I came up with these 2.

 

https://www.claymansupplies.co.uk/Products/Earthenware/1070~12@5 1100-1220°C (Cone 03-6)  Earthenware/Mid-Range Stoneware, white clay. 

https://www.claymansupplies.co.uk/Products/Earthenware/1090~12@5 red groggy earthenware that is rated to ^6

 

Don't know anything about them other than what I read. Wonder if you could get some more detailed info from Clayman? Must be very frustrating have so few choices for this firing range. (they are in Chichester)

[Joseph Fireborn]

It's very possible you just have to find a decent seller of clay. I don't even glaze a lot of the insides of vases that I have made for personal use to keep roses from my flowers outside in. I have yet to have a problem with weeping after months of water and roses all summer long.  So it's definitely possible, just gotta get the right body and fire it to the right temp. Don't give up.

[glazenerd]

 

(Cone 03-6)  Earthenware/Mid-Range Stoneware, white clay.

Min: that broad of a firing range explains a lot: way too broad. I would however use this clay for cone 6; only because it is at the top of the firing range. Which I would assume to mean: the highest chance of vitrification.

 

Nerd

[Min]

 

 

(Cone 03-6)  Earthenware/Mid-Range Stoneware, white clay.

Min: that broad of a firing range explains a lot: way too broad. I would however use this clay for cone 6; only because it is at the top of the firing range. Which I would assume to mean: the highest chance of vitrification.

 

Nerd

 

 

Yup, thats what I think too. And the other one I posted 04 - 6 and they call it earthenware 

Eyeopening how few clays there are to choose from for ^6

[ayjay]

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.

[PottaFella]

 

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.

 

 

 

Ayjay, that is very interesting, I know the ES5 is very well thought of, and it's a lovely clay to work/throw with, but I can only describe what has happened in my using it. Perhaps there is some other factor involved, but for now I am firing it higher (cone 8) to try and ensure my vessels leak-proof.  Generally the glazes I've been using have been from the Michael Bailey book, so perhaps there is a problem here, using cone 6 glazes with a body aimed at higher temps? Whatever's been happening, it is certainly been challenging for me and I have much appreciated the support and advice of the generous potters on this amazing forum.   I'd be very interested to read your firing schedule Ayjay, and many thanks again.

 

PS: I've just had a look at Colin Jone's website where in his techniques he says he glaze-fires to about 1240c.  I've just taken some re-fired pots out of my electric kiln, fired to 1220c with a 30min soak – cone 8!!!

[Celia UK]

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!

[High Bridge Pottery]

I would make sure to ask questions about their 'earthenware' that is rated up to cone6. I bet there is a good cone6 stoneware hidden in there and just sold as earthenware.

 

I have a day off work tomorrow so I think I will try ringing them, see if I can get any more useful data out of them. I have always been at cone9-10 so never really looked too hard about cone6 clay.

 

Celia I have used some B17C at cone9 and still felt it wasn't completely mature. Not that I tested it's absorption, just a feeling in my boots. 

[PottaFella]

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!

 

Thanks Celia, good luck with the firing. I just read your profile very interesting.

 

I've been using stoneware, terracotta, porcelain (a little) and just about to try some white earthenware clay which I hope may give more flexibility to illustrate with a nice white background (stoneware always seems to end up creamy-coloured).

 

One of my main reasons to fire cone 6 for stoneware was to prolong the life of electric elements. I reckon if your kiln behaves like mine, then your 1200c with a 30 min soak will be about cone 7 - be interested to know how it works out!

[ayjay]

 

  I'd be very interested to read your firing schedule Ayjay, and many thanks again.

 

PS: I've just had a look at Colin Jone's website where in his techniques he says he glaze-fires to about 1240c.  I've just taken some re-fired pots out of my electric kiln, fired to 1220c with a 30min soak – cone 8!!!

 

 

Here's how I fire mine Oly, all temperatures in °C, I don't think there's anything special or unusual in my firing, but it seems to work OK.

 

My pot are always completely dry before I fire them, I'll usually have a kiln half filled while I wait for more pots to fill it and I'll often candle it for a couple of hours every few days just to be on the safe side, the pots that go in later will probably have been in the wife's airing cupboard for a couple of days and I usually candle the whole lot again before I actually fire them.

 

I nearly always fire to 1210,  I've sometimes gone down to 1200 and sometimes up to 1220, (or anywhere in between, with different hold times) but always in between those two figures.

 

Bisque fire.

@ 100 - 600

@ 200 - 1050

hold 15 mins.

 

Glaze fire.

@100 - 600

@175 - 1100

@50 - 1210

hold 15 mins

 

A good clear liner glaze for ^6. (add Tin Oxide  - 4  for a White liner glaze) this glaze dries nicely on the pot can be handled without leaving marks and any runs or drips will rub off quite easily with a finger/soft rib etc.

 

Std. Borax frit - 20

Wollastonite  - 15

Potash Feldspar - 20

China Clay - 20

Talc - 6

Flint - 19

 

Colin does like to get his glazes moving, some of mine move plenty as it is, I wouldn't want to fire them any hotter.

 

 

Here's a typical 6 cone from one of my firings.

 

[PottaFella]

These people do a range of clays for cone 4 - 7, which would seem worth a go for cone 6 firing. I've no idea about the clays, and so this isn't a recommendation, but they are sold as mid-fire, so are presumably formulated for that purpose. There is a minor snag in that they are in Scotland, but hey...

 

Scotclay

 

Oly - as you are in Kent, you could ask Roger at The Clay Cellar - he was always on at me to fire low (for environmental reasons), so he should be able to suggest a clay!

 

The Scotclay range looks amazing - but I've contacted them and they are packing up making it, though they still have some stocks

[Sputty]

.

[Mark C.]

(There must surely be a source somewhere in the UK - cone 6 is pretty popular now, as a concept at least!)

​I'm shocked that cone 6 hobby craze has not spread to the UK.

Is hobby ceramics still cone 06-08? In UK .Are Paint your own shops still around there??Or slip making shops?

I know ceramics on the manufacturing level got shipped to China (trent/Stokes area)

I'm curious about. the hobby side over there?

I met a english fed ex driver who migrated here to US after his job in ceramics at Trent/Stokes went to Asia.

[Marcia Selsor]

Cone 6 has grown in popularity because it uses less energy and is greener , its cheaper, and the results can be as attractive as any ^9-10. I worked for 20 years on ^6reduction glazes and the last 16 on ^6 oxidation. The results are actually very pleasing and look like ^10. So please continue to investigate. I'd recommend Michael Baileys ^6 Galzes Book since he is based in the UK and the chemicals will be more familiar to you.

Marcia

[MartinB]

Most online suppliers have a section for cone-6 glazes but pretty much all clays are just listed as stoneware and given a broad firing range.

 

I'm interested in a cone 6 porcelain but there are none listed specifically as that, though several say 1240-1300 firing range. I assume at the lower end I would be sacrificing some translucency and strength...

 

I've ordered sample packs of a few and am going to run some tests. I'm happy enough re-formulating my glazes to work at cone 6 but if I can't get a nice body I'll have to stick to higher firing.

[PottaFella]

It is interesting, the clay sold as terracotta has a firing range up to 1220 but all stoneware goes up to 1260/1300.

 

I think you are probably right that clays sold as stoneware are cone10 clays even if their range goes from 1080-1280. That doesn't mean there is not one out there that would suit cone6 but I have never found much useful data about the clays out there.

 

I would try a terracotta rated to 1220 and see if you have any luck.

 

There is one here rated to 1120c but also says 'will vitrify at high stoneware temperatures' after having a look through valentines clay it looks like a few possible cone6 bodys could be filed under white earthenware/terracotta.

 

"KGM Body     can be fired 1080-1120oC

White to Off White at higher temperatures.

Smooth. Cost effective white earthenware clay which will vitrify at high stoneware temperatures. Due to very fine grog will give a light speckle at the highest te

 

"Potclays 1141 Studio White Earthenware (LT25)

White.

Smooth. Ivory white very plastic white clay for throwing.1100-1220oC"

 

Potclays actually give this clay a vitrification range of 1180-1250 but the firing range above. Who decides to put these things.

http://www.ctmpotterssupplies.co.uk/PotclaysTechnicalInformation.pdf

 

That Potclays information sheet makes very interesting reading. Strikingly, most of their stoneware clays vitrify from 1260c – quite a long way away from cone 6. Their '151-1117 Buff Stoneware' reads as vitrifying form 1240 so that's going to be one a try. If Earthstone is anything like the potclays bodies, it would explain why at cone 6 they may weep – some proper absorbtion tests is obviously the only way to clear this up.