Cone 6? Cone 8? Cone 10? Etc Etc

Jay

OK, I would like to start the information flowing. I know there are potters who fire to Cone 6 and say it is outdoor capable, they use a clay body that is designed for cone 6 firing. I can not see why this is wrong.

Others, say you got to fire to cone 10 to get that real outdoor hardness. Of course they use a claybody for this temp.

Others feel that once you pass the cone 6 level of firing, you have high fire stoneware, it is vetrified (sp) and as hard as it needs to be regardless of the temperature limits of the claybody.

My pots, fired at a local studio are fired to approx cone 8 1/2. Why approx, because the kiln that they are fired in is an extremely large gas kiln, when it is opened after firing, cones in various locations show total melt of #8 with #9 being melted totally or in some locations only bent over. My pots are winter hard in my opinion, I've been freezing them and melting them with wet soil in the freezer.

So, know that we have some 'names' that we can trust on this board. Names that are, in my opinion, very knowledgeable whats the word? Is in fact cone 6 through 10 OK? is the cone 10 a partial snob thing? Whats the story?

As an aside, if you are not going to glaze a pot what is wrong with a single fire to cone 6 to 10, eleminating the bisque fire?

Questions questions.... now for your answers....

thanks
Jay

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Think before you act... then think again... no good comes from rushing

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muddslinger

Hi Jay,
I don’t know if I’m one of the “names you can trust”, but here’s my two cents…
According to the clay technician at Standard Clay, there is no reason other than aesthetic (reduction, etc) effect to fire to cone 10. She said almost all the clay they sell for outdoor use is fired to cone 6. There are many cone ten clays that wouldn’t be appropriate for outdoor use. I don’t think it has as much to do with temperature (once past 6) as it does virtuosity and firing the clay to maturity. The reason low fire (in the 06 range) aren’t suitable for outdoor use it that they are simply too porous and absorbent, and soft. There are two schools of thought on the outdoor durability thing: 1. The clay is so vitreous that little or no water is absorbed so that when it freezes there’s not enough expansion to do any damage. 2. The clay is somewhat absorbent allowing some capillary room for expansion when freezing.
Everything I’ve read seems to agree that absorption should be less than 3%.
I’m not sure about the cone 10 snob thing. I think its more a matter of improvement in cone 6 bodies over recent years. IMHO if a clay body meets the absorbency guidelines when fired to maturity, it should survive quite well. I’ve been freezing and thawing my pots daily.They're made with two cone 6 stoneware and one porcelain body for over a month with no signs of stress. I’ve got them filled with saturated peat.
I suggest you talk to the clay tech. At Standard, (If that's the brand you use) she’s very friendly and helpful.

It is possible to “once fire” a pot. Some potters use this method and it can even be done with glaze if you use the right clay and glaze. Keep in mind though that the bisque firing eliminates most of the chemical water in the clay and the first 1000 degrees of temperature increase needs to be pretty gradual. Possibly more gradual than the “ramp” of temperature increase your teacher uses in his glaze firing. I’d recommend throwing a little green pinch pot in the glaze kiln to test before you try it with any of your good pots.

When are you going to have some new pots to share?
Best,
Kevin

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Hand Crafted Bonsai Pots by Kevin Thompson

Jay

Kevin, Yes you are 'one' of the names I can trust. If I'm reading you correctly, you feel that the improvements in Claybody has allowed for cone 6 clay to be OK for outdoor long term use. This is based on the potential absorption rate of the clay, under 3% you said. I have noticed that differing clay bodies have differing absorption rates.... and then the specific clay body has a differing rate listed for differing firing temps. Can you touch on this.

As for new pots, I was away from the studio for a while but I am getting back 6-8 new pots and there is a couple of larger ones in process, probably not going to be ready for a couple of weeks. I am leaving for a few days this evening (doing the house hunt thing) but will try and get up some new stuff to show all.

Jay

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Think before you act... then think again... no good comes from rushing

muddslinger

Hi Jay,
The two stoneware clays I'm using are of the wide range variety (cone 4-10) Standard has many clays like this. Of course, if you fire closer to the higher range, the pot is going to be harder and more vitreous. Both the clays I used in my first batch of bonsai pots fall well under the 3% absorption rate when fired to cone 6 (7) and have been taking some pretty serious abuse over the last five weeks. It's hard to say weather the same clay fire near the top of it's range would be more weather resistant or not. I guess it depends on weather you think some porosity or almost none is best. I think both schools of thought are probably valid.
About four years ago, I worked on a outdoor mural for a local library where I made a few tiles and most of them were made by children. This was done with a Laguna cone 6 stoneware body that was recommended by a potter in NH that does mostly outdoor work. It's just fine so far.
I think most cone 6 to 10 clays will work fine for outdoor use under the conditions that most bonsai are exposed to. Just to be on the safe side, I'll stick with clays that are recommended for outdoor use.
Best,
Kevin

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Hand Crafted Bonsai Pots by Kevin Thompson

Dale Cochoy

Jay,
I'll try to give my opinion on this quickly without too much typing..
Cone 6 clays can be vitrified to 2 1/2ish % absorption if they are constructed so, and this works fine for bonsai pots in the north. I've done this for years and still do. I have a couple clays I really like for slab building that are cone6 and I've never had a winter freezing problem ( that I know of )
And, cone 9/10 clays are also vitrified to the 2-21/2ish % range if so constructed and , of course, excellent in winter. Now, "mudslingers" comment on cone 10 "snob" aside, the differences as I see it: ( remember I do both)
The cone 6 clays can't compare with the beautiful cone 10 clays available. Gorgeous. You can fire cone 6 clays in reduction to nice effects but the cone ten reduced clays are wonderful. Ditto with glazes.
the other thing is "Durability" . Cone 10 fired clays are more durable ( IMHO) than cone 6 clays of the same absorption %. They just pass the abuse test of clinking, bumping, chipping better.
As I said, I daily do both and there is a reason for each I use whether cone 6 or 10, so I'm not "snobbing" , just a few opinions.
Regards,
DaleCochoy
Yakimono no Kokoro Bonsai Pottery

__________________
________________________________
If you want to be Different....
You have to DO something Different!
__________________________________________

Some people NEVER take the time to do a job right the first time....
but, they always seem to make the time to do it over again...
____________________________________________
Dale Cochoy
Wild Things Bonsai Studio
Yakimono no Kokoro Bonsai Pottery
Hartville, Ohio

muddslinger

Hi Dale,
I just wanted to point out that the "snob" comment was not mine, I was merely responding to a question Jay had. I think if you go back over the thread you'll see that nobody was insinuating anyone was a snob.
I agree with everything you mentioned in your post and never intended to ruffle any feathers. I apologize if it came off wrong.
Best,
Kevin

Originally posted by Jay


Originally posted by muddslinger


Originally posted by Dale Cochoy

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Hand Crafted Bonsai Pots by Kevin Thompson

Jay

Dale, Kevin is not the guy with the Cone 10 snob comment, that was me.

I was not saying it was a fact, just asking the question. Snob is obviously not the correct word for the situation and I should withdraw that statement.

I should have said ' is firing to cone 10 necessary for the pot, or is it done just because it has always been done that way'. Bad choice of words, Hopefully no feathers were ruffled, or individuals hurt.

Either way, Dale gave a fairly complete explanation. If I understand it correctly, the percentage of absorption is the key. Keeping it down below 2% will give a durable cold weather pot. The cone 10 firing will also, in reduction, allow for better visual results. Also I hear your (Dale) feeling that over the long run the higher fired clay will be more durable.

Thanks
J

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A Bonsai student living with his trees at N 44.37 W 77.49...
Think before you act... then think again... no good comes from rushing

Dale Cochoy

no feathers ruffled here guys. I didn't mean it to sound as if there were.
Dale
P.S. Jay, do you live anywhere near OrangeCounty Choppers? I want to visit!!
Dale "Built custom chopper years go" Cochoy

__________________
________________________________
If you want to be Different....
You have to DO something Different!
__________________________________________

Some people NEVER take the time to do a job right the first time....
but, they always seem to make the time to do it over again...
____________________________________________
Dale Cochoy
Wild Things Bonsai Studio
Yakimono no Kokoro Bonsai Pottery
Hartville, Ohio

Jay

Dale, Thanks for being understanding. Can not (and should never) speak for others but sometimes I (we) use written shortcuts or questionable phrasing that in hindsight should be avoided or explained in detail.

As for Orange County Choppers, they are in my area, I think they are actually fairly close to Craig Cowing who stops by here from time to time. I will find out where they are and how to get there for you, but give me some time, the next few weeks will see me extremely busy with my packing and moving.

Assuming you are coming again to the Mid-Atlantic this coming spring, you could make a side trip. They are approx 1 to 1 1/2 hours north of where you'll be.

Jay

__________________
A Bonsai student living with his trees at N 44.37 W 77.49...
Think before you act... then think again... no good comes from rushing