Firing Stoneware

[savant]

Have not fired any stoneware yet in my electric kiln but am wanting to, I will be using cone 7-10 stoneware clay with a cone 6 glaze. Are there any problems with this?

Should I put any sand, wadding, etc., under my pots? I use stilts on my earthenware when I glaze fire, should I do the same with the stoneware?

Just a quick run through on how to do this would be a great help.

Thanks for the help

[Guest JBaymore]

Your cone 7-10 stoneware will not be a mature body at cone 6. It really isn't at cone 7. So the clay will be more porous than what is likely desireable. This underfiring of the body may also impact the fit of the glaze to the body (coefficient of reversible thermal expansion differences).

 

All of this can have potential impacts in many ways... almost too numerous to fully list right now. So to start with...............

 

Why did you decide to fire to cone 6 with that particular clay body?

 

best,

 

.................john

[savant]

Your cone 7-10 stoneware will not be a mature body at cone 6. It really isn't at cone 7. So the clay will be more porous than what is likely desireable. This underfiring of the body may also impact the fit of the glaze to the body (coefficient of reversible thermal expansion differences).

 

All of this can have potential impacts in many ways... almost too numerous to fully list right now. So to start with...............

 

Why did you decide to fire to cone 6 with that particular clay body?

 

best,

 

.................john

 

 

 

hey John, thanks for responding to my question, well I have this stoneware clay, like I said that is rated as ^7-10. I have bisqued fired it to ^06 at this point wanted to use a

liner glaze and was going to use red iron oxide on the outside, the glaze is a ^6 glaze was that is where I get lost , should I be using a glaze that fires to a hotter temp?

What would happen if I use the ^6 glaze?

[Marcia Selsor]

Ideally you should use a glaze that matures at the same temperature as the clay. As John mentioned, they need to "fit" together. If you have ever used a high temperature glaze with low fire glazes without going to the maturing point of the clay, you end up with serious crazing.

If you fire the ^6 glaze hotter than is the maturing temperature, it can run or it can boil up literally.

 

Marcia

[Guest JBaymore]

I have bisqued fired it to ^06 at this point wanted to use a

liner glaze and was going to use red iron oxide on the outside, the glaze is a ^6 glaze was that is where I get lost , should I be using a glaze that fires to a hotter temp?

What would happen if I use the ^6 glaze?

 

 

The clay itself will not be as strong as it could/ should be. It will be more porous than a "stoneware" should be. Functionally it will absorb more water / liquid than a good stoneware should. In general fact, it will not exhibit the traits structurally that likely you are desiring in your change to "stoneware".

 

The glaze will be seriously overfired if you take the body to the range it should be fired into ... cone 9-10. That will result at the LEAST in serious running. It may aslo cause some of the chemistry to "vaporize" out of the glaze (don't know the recipie or formula) thereby changing its composition. This will change the character of the glaze. It may end up looking like forzen 7-up soda... all fizzy and bubbly. Or with craters. Or with the color burned out. The list or potential issues is long.

 

If you fire the glaze to cone 6 on the non-matured body 7-10 body, the bond at the clay/glaze interface layer will not really develop very much as it does in properly formulated stoneware. That decreases the stregnth of the overall piece as well as the strength of the glaze itself. The COE I already mentioned before likely will not match... and the glaze will likely craze. That crazing will further weaken the piece. Crazing will also let liquid through to the porous clay underneath, exacerbating any moisture issues.

 

If the body absorbs moisture, use in something like a microwave will be problematic due to the moisture trapped in the clay even though the piece seems "dry". Repeated microwave use will cause the piece to crack. The piece will get dangerously hot in aq microwave.

 

The list of potential issues is long.

 

best,

 

............john

[AmeriSwede]

I have bisqued fired it to ^06 at this point wanted to use a

liner glaze and was going to use red iron oxide on the outside, the glaze is a ^6 glaze was that is where I get lost , should I be using a glaze that fires to a hotter temp?

What would happen if I use the ^6 glaze?

 

 

The clay itself will not be as strong as it could/ should be. It will be more porous than a "stoneware" should be. Functionally it will absorb more water / liquid than a good stoneware should. In general fact, it will not exhibit the traits structurally that likely you are desiring in your change to "stoneware".

 

The glaze will be seriously overfired if you take the body to the range it should be fired into ... cone 9-10. That will result at the LEAST in serious running. It may aslo cause some of the chemistry to "vaporize" out of the glaze (don't know the recipie or formula) thereby changing its composition. This will change the character of the glaze. It may end up looking like forzen 7-up soda... all fizzy and bubbly. Or with craters. Or with the color burned out. The list or potential issues is long.

 

If you fire the glaze to cone 6 on the non-matured body 7-10 body, the bond at the clay/glaze interface layer will not really develop very much as it does in properly formulated stoneware. That decreases the stregnth of the overall piece as well as the strength of the glaze itself. The COE I already mentioned before likely will not match... and the glaze will likely craze. That crazing will further weaken the piece. Crazing will also let liquid through to the porous clay underneath, exacerbating any moisture issues.

 

If the body absorbs moisture, use in something like a microwave will be problematic due to the moisture trapped in the clay even though the piece seems "dry". Repeated microwave use will cause the piece to crack. The piece will get dangerously hot in aq microwave.

 

The list of potential issues is long.

 

best,

 

............john

 

 

 

 

I'm not much help in answering to your problem, savant, but thought maybe John could expand on this thought ...

 

In trying to use this clay body (^7-10) with this glaze (^6), would it work and be a decent compatible 'fit' if the stoneware

was fired to ^9-10 as bisque and then glazed and fired to ^6? I don't think it would be the normal approach but seems I've

read that many ceramists do fire their items at a higher temp and often apply many (over/under?) glazes at lower temps as

there is more diversity of brighter colors at the lower temperatures. That would mature the clay, but how will the glaze be affected

for 'fit'? Possibly warming the ceramic a tad bit before glazing would help the glaze to go on the less porous matured clay, or would

it not?

 

....Rick

[richardsan]

nope, i wouldn't do that either...is there no glazing solution to fit the clay body? have you looked for an acceptable recipe for it?

^7-10 wouldn't be a bisque firing. those are vitrifying temperatures.

vitrify: convert (something) into glass or a glasslike substance, typically by exposure to heat.

liquids[glaze] would have trouble adhering to a fully matured[vitrified] object.

please read something that explains what the purpose of a bisque fire at the much lower temperature is for,

and what happens to the clay at those lower temps...then read what happens [chemically] to clay and glaze at the higher temp.

i'd do a test on your already [properly] bisqued ware to see if your RIO stain will be acceptable on the outside at ^7-10 and while that is firing, research a good liner glaze for ^7-10

so you can marry your clay, staining and glazing scheme.

 

quite simply, though, is you prob. don't need a liner glaze if your ware is well made, just test the RIO stain at the maturing temp. the vitrification at ^7-10 may suffice.

is this for food?

 

 

I'm not much help in answering to your problem, savant, but thought maybe John could expand on this thought ...

 

In trying to use this clay body (^7-10) with this glaze (^6), would it work and be a decent compatible 'fit' if the stoneware

was fired to ^9-10 as bisque and then glazed and fired to ^6? I don't think it would be the normal approach but seems I've

read that many ceramists do fire their items at a higher temp and often apply many (over/under?) glazes at lower temps as

there is more diversity of brighter colors at the lower temperatures. That would mature the clay, but how will the glaze be affected

for 'fit'? Possibly warming the ceramic a tad bit before glazing would help the glaze to go on the less porous matured clay, or would

it not?

 

....Rick

 

 

 

 

[Pres]

I have bisqued fired it to ^06 at this point wanted to use a

liner glaze and was going to use red iron oxide on the outside, the glaze is a ^6 glaze was that is where I get lost , should I be using a glaze that fires to a hotter temp?

What would happen if I use the ^6 glaze?

 

 

The clay itself will not be as strong as it could/ should be. It will be more porous than a "stoneware" should be. Functionally it will absorb more water / liquid than a good stoneware should. In general fact, it will not exhibit the traits structurally that likely you are desiring in your change to "stoneware".

 

The glaze will be seriously overfired if you take the body to the range it should be fired into ... cone 9-10. That will result at the LEAST in serious running. It may aslo cause some of the chemistry to "vaporize" out of the glaze (don't know the recipie or formula) thereby changing its composition. This will change the character of the glaze. It may end up looking like forzen 7-up soda... all fizzy and bubbly. Or with craters. Or with the color burned out. The list or potential issues is long.

 

If you fire the glaze to cone 6 on the non-matured body 7-10 body, the bond at the clay/glaze interface layer will not really develop very much as it does in properly formulated stoneware. That decreases the stregnth of the overall piece as well as the strength of the glaze itself. The COE I already mentioned before likely will not match... and the glaze will likely craze. That crazing will further weaken the piece. Crazing will also let liquid through to the porous clay underneath, exacerbating any moisture issues.

 

If the body absorbs moisture, use in something like a microwave will be problematic due to the moisture trapped in the clay even though the piece seems "dry". Repeated microwave use will cause the piece to crack. The piece will get dangerously hot in aq microwave.

 

The list of potential issues is long.

 

best,

 

............john

 

 

 

One other potential issue here is the fact that your pots will not have glazed bases as in the earthenware you fire now. Stilting is not appropriate at higher temps. So the unglazed bases are a source of absorption for water or anything else. Not dishwasher safe, and at the same time the above mentioned problems will be compounded.

[jjstlouis]

Will Mayco Foundations lowfire glaze stay on cone 6-10 highfire stoneware? or will it craze or run?  I have an abundance of stoneware, but only lowfire glazes.

[oldlady]

it is very hard being a new ceramic enthusiast.  it is a very complex art/science.  you are not the only one who has this confusion. this question keeps coming up.   the answer is NO.  DO NOT DO THIS. there are lots of explanations of why it won't work.  please notice that you have said the glaze is made for lowfire work.  if you put it on stoneware and fire it to high temperatures it will run off the pot and all over the shelf.  get some lowfire clay or get some highfire glaze.  they do NOT work together.   

 

do not be discouraged by my answer.  it is easier to face the facts than to try something that will not work.  

 

what is your clay experience?  do you work with an instructor?  do you know any other potters?  is this the only source of information you have access to?

[Chilly]

Will Mayco Foundations lowfire glaze stay on cone 6-10 highfire stoneware? or will it craze or run?  I have an abundance of stoneware, but only lowfire glazes.

 

You can try it, as the only way to believe it is to see it for yourself, but as OldLady says, it (probably) won't work.  You could also try firing your stoneware clay, covered with lowfire glaze to the recommended glaze temperature, but again, it (probably) won't work.  If you do fire this lowfire glaze to stoneware temps, make sure you protect your kiln shelves by putting large cookies under the pots.

 

I was told repeatedly by my first pottery tutor "it won't work", but the reasons and results were never explained.  I had to try it for myself to believe it.  And, sometimes it does work.  It's a bit like that "wet paint" sign, someone always has to touch.......

 

Enjoy the experimentation, sometimes that can be just as much fun and satisfying as getting a proper end result.

[bciskepottery]

Make some test tiles. Apply the low fire glaze to only the top 1/4 to 1/3. Fire and see how the glaze moves.

 

Where this might work and produce interesting results is applying the low fire glaze over a cone 6/10 glaze. Again, test before trying on large items. You may only need to put the low fire on the top quarter or rim of the pot.

[MatthewV]

Meh, with low-fire you can do just about anything. If you have ∆10 clay and low-fire glazes, just do low-fire pieces. They won't hold water well. So make Art, sculptures and other decorative experiments.

 

Just don't make mugs and bowls and bottles and such. Flower pots would be fine. So would dragons and angels and gnomes...