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Bright Colors - Especially Orange

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Very interesting discussion! I have similar questions. I trying to make brightly colored, highfire, functional tableware and oven ware. I recently switched clay from Phoenix to Loafer's Glory in order to get a whiter/smoother body. Highwater ranks this clay at cone 6-10 (and I agree it seems crazy to me to have such a large range for vitrification).

 

I have been firing at cone 10 in gas reduction and the clay body appears to vitrify. I want to use bright colored underglazes (especially orange) on a white body (Loafer's Glory). But the oranges come out brown and muddy. I understand that the colors will be brighter and hold up better in lower firings like cone 06 or even cone 6 oxidation. But I want to make sure the ware is fucntional and vitrified so that can be used in the dishwasher, microwave, oven, etc.

 

So I'm trying to figure out what to do. Should I just underglaze and fire to cone 6 and hope for the best, or should i try a high fire oxidation instead of reduction, or should I switch to a clay body that matures at cone 6--like Little Loafers——OR——can I bisque the pieces to cone 10 (so that they are fully vitrified) and then spray on an underglaze and clear coat and refire down to cone 06 or 6—or will the color/glaze not absorb b/c it is vitrified?

 

What I'm trying to ask is—how can I get bright underglaze colors on highfire, vitrified stoneware--or porcelain for that matter. Of course I have seen this done all over the place. There has to be an simple solution, no?

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Very interesting discussion! I have similar questions. I trying to make brightly colored, highfire, functional tableware and oven ware. I recently switched clay from Phoenix to Loafer's Glory in order to get a whiter/smoother body. Highwater ranks this clay at cone 6-10 (and I agree it seems crazy to me to have such a large range for vitrification).

 

I have been firing at cone 10 in gas reduction and the clay body appears to vitrify. I want to use bright colored underglazes (especially orange) on a white body (Loafer's Glory). But the oranges come out brown and muddy. I understand that the colors will be brighter and hold up better in lower firings like cone 06 or even cone 6 oxidation. But I want to make sure the ware is fucntional and vitrified so that can be used in the dishwasher, microwave, oven, etc.

 

So I'm trying to figure out what to do. Should I just underglaze and fire to cone 6 and hope for the best, or should i try a high fire oxidation instead of reduction, or should I switch to a clay body that matures at cone 6--like Little Loafers——OR——can I bisque the pieces to cone 10 (so that they are fully vitrified) and then spray on an underglaze and clear coat and refire down to cone 06 or 6—or will the color/glaze not absorb b/c it is vitrified?

 

What I'm trying to ask is—how can I get bright underglaze colors on highfire, vitrified stoneware--or porcelain for that matter. Of course I have seen this done all over the place. There has to be an simple solution, no?

 

For a sure fire orange in ^10 reduction you may need to use Degussa stains.

Marcia

 

 

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Very interesting discussion! I have similar questions. I trying to make brightly colored, highfire, functional tableware and oven ware. I recently switched clay from Phoenix to Loafer's Glory in order to get a whiter/smoother body. Highwater ranks this clay at cone 6-10 (and I agree it seems crazy to me to have such a large range for vitrification).

 

I have been firing at cone 10 in gas reduction and the clay body appears to vitrify. I want to use bright colored underglazes (especially orange) on a white body (Loafer's Glory). But the oranges come out brown and muddy. I understand that the colors will be brighter and hold up better in lower firings like cone 06 or even cone 6 oxidation. But I want to make sure the ware is fucntional and vitrified so that can be used in the dishwasher, microwave, oven, etc.

 

So I'm trying to figure out what to do. Should I just underglaze and fire to cone 6 and hope for the best, or should i try a high fire oxidation instead of reduction, or should I switch to a clay body that matures at cone 6--like Little Loafers——OR——can I bisque the pieces to cone 10 (so that they are fully vitrified) and then spray on an underglaze and clear coat and refire down to cone 06 or 6—or will the color/glaze not absorb b/c it is vitrified?

 

What I'm trying to ask is—how can I get bright underglaze colors on highfire, vitrified stoneware--or porcelain for that matter. Of course I have seen this done all over the place. There has to be an simple solution, no?

 

For a sure fire orange in ^10 reduction you may need to use Degussa stains.

Marcia

 

 

 

 

THANK YOU MARCIA! I'm going to try it asap!

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Well, I made a couple test glazes with the Degussa orange stains. Still comes out BROWN in cone 10 reduction.

 

The closest orange I got was kind of a burnt sienna by adding 10% of the stain to a Haynes white recipe on the Loafer's Glory stoneware. Any suggestions what I should try next? Should I add more stain? Is there a better base recipe? What if I tried mixing a stain or slip and clear over? (I am working with bisque ware).

 

Commercial orange underglaze seems to work fairly well, if not a bit smokey, but the lightest bit of clear glaze turns it completely brown.

 

Any suggestions please?

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Well, I made a couple test glazes with the Degussa orange stains. Still comes out BROWN in cone 10 reduction.

 

The closest orange I got was kind of a burnt sienna by adding 10% of the stain to a Haynes white recipe on the Loafer's Glory stoneware. Any suggestions what I should try next? Should I add more stain? Is there a better base recipe? What if I tried mixing a stain or slip and clear over? (I am working with bisque ware).

 

Commercial orange underglaze seems to work fairly well, if not a bit smokey, but the lightest bit of clear glaze turns it completely brown.

 

Any suggestions please?

I think it should be added to a clear glaze over a white background like porcelain or a white slip. Putting a stain in a white glaze impedes the stain because there is an opacifier in the white glaze which may cause ill effects. Your best bet would be a clear glaze with 10% stain on porcelain. Any reason you are not using oxidation for this color?

Marcia

 

 

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Thanks Marcia, I did do tests with of the stain (10%) in a Hamada clear base--also turned brown. The Loafer's Glory is a white stoneware, I'm going to try porcelain next time.

 

Here's my dilemma: I am using a clay body that has a firing 'range' of 6-10. I'm making functional ware, and I want to be sure it is vitrified, so I want to fire to cone 10. However, the studio I'm working at (St Pete clay company) only fires cone10 reduction. They also do a cone 6 oxidation, but I worry about the durability of the ware at cone 6.

 

Maybe I should fire to cone 10. Then glaze and down-fire in oxidation?

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Thanks Marcia, I did do tests with of the stain (10%) in a Hamada clear base--also turned brown. The Loafer's Glory is a white stoneware, I'm going to try porcelain next time.

 

Here's my dilemma: I am using a clay body that has a firing 'range' of 6-10. I'm making functional ware, and I want to be sure it is vitrified, so I want to fire to cone 10. However, the studio I'm working at (St Pete clay company) only fires cone10 reduction. They also do a cone 6 oxidation, but I worry about the durability of the ware at cone 6.

 

Maybe I should fire to cone 10. Then glaze and down-fire in oxidation?

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Guest JBaymore

As you explore reds and oranges.........

 

Remember that if you use a glaze or underglaze or overglaze containing cadmium compounds, encapsulated or not, you then need to comply with the FDA regulations governing the use of cadmium on ceramic wares.

 

To my knowledge the law has not yet caught up with the idea of the encapsulation. My guess is the data is not yet fully in.

 

best,

 

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

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Oh wow. So then do I understand correctly that cadmium colorants are not FDA approved for functional ware, even in encapsulated stains--despite Cerdec/Degussa's claims that they are food safe?

 

If so, how is that one can buy all sorts of red/orange ceramic dinnerware just about everywhere, from Walmart to Pier One? Are these manufactured dishes mostly likely low fire cadmium free colors?

 

Is there no way then to make orange, high fire, functional pottery?

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Guest JBaymore

Oh wow. So then do I understand correctly that cadmium colorants are not FDA approved for functional ware, even in encapsulated stains--despite Cerdec/Degussa's claims that they are food safe?

 

If so, how is that one can buy all sorts of red/orange ceramic dinnerware just about everywhere, from Walmart to Pier One? Are these manufactured dishes mostly likely low fire cadmium free colors?

 

Is there no way then to make orange, high fire, functional pottery?

 

Foster,

 

I have been teaching ceramic chemistry and toxicology for ceramic artists at he college level since sometime back in the 70's.

 

It is not that they are "not FDA approved", it is that if you use them in the USA there are specific FDA testing and recordkeeping standards that you must follow to comply with the law. That is what I was saying in the last posting. There are also limitations on the locations that cadmium bearing compounds can located be relative to the interior / exterior of certain pieces. These standards vary with the exact nature of the ware in question. So something like a cup is different from something like a pitcher, for example.

 

As to the commercial pottery manufacturers, they are in all likelyhood (hopefully) complying with the laws as specified. Large producers will have the resources to do this more easily than a studio artist. Otherwise they open themselves up to large fines....and also the potential of a product liability lawsuit in the case of documentable damages.

 

The FDA currently only regulates the leaching of two chemicals in ceramic glazes; lead and cadmium compounds. If you live or sell in California however, that state has regulations that are MORE stringent than the FDA laws.

 

It is not that you cannot produce this stuff safely. But the procedures necessary to REALIABLY assure that the wares are safe are more the province of industry, with tight glaze batching, glaze application, and sophisticated firing controls. Us stuudio potters tollerate variables that industry does not allow. Makes tight glaze control problematic.

 

Also the testing requirements will add costs to the production cost of the wares. Another reason it is more difficult for the small producer. You need to have a well structured regular sampling program that will assure that the fired wares are safe. This is going to cost you something. The testing will have to be by a lab....this is not "potter level chemistry" here.

 

Even if you make "non-functional" vessel type wares.... if the object could reasonably be used by a purchaser for food use, there are even specific labeling requirements that must be put on the ware in certain ways, and in certain sizes. Just having a hand tag that says "do not use for food" is by FAR not enough, nor legal.

 

Also the encapsulated stains are not necessarily unsafe. I am not saying that. They are supposed to do what they say they do. But the onus of responsibility for making sure that they DO that is on the producer of the end-use object. As in "YOU". The maker of the pot. The stain supplier does not indemnify the manufacturer (you again) that uses its products. They say it... but you are responsible for it by law.

 

Go to FDA.gov and start researching this stuff. Also get a copy of "Keeping Claywork Safe and Legal" by Mononna Rossol ...and sold by NCECA.

 

Too many studio potters do not know about this kind of stuff. Too few schools teach it.

 

Hope that helps.

 

best,

 

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

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Thanks Marcia, I did do tests with of the stain (10%) in a Hamada clear base--also turned brown. The Loafer's Glory is a white stoneware, I'm going to try porcelain next time.

 

Here's my dilemma: I am using a clay body that has a firing 'range' of 6-10. I'm making functional ware, and I want to be sure it is vitrified, so I want to fire to cone 10. However, the studio I'm working at (St Pete clay company) only fires cone10 reduction. They also do a cone 6 oxidation, but I worry about the durability of the ware at cone 6.

 

Maybe I should fire to cone 10. Then glaze and down-fire in oxidation?

 

 

If you bisque fire Loafers Glory to cone 10 it will vitrify and you will not be able to glaze and down-fire it to cone 6 in oxidation. Once vitrified, the clay body will not absorb the water from the glaze. At cone 10, Highwater states the absorption rate is less than 1%; at cone 6, the absorption rate is 3.9%. Firing Loafers Glory to only cone 6 will not provide you with a fully vitrified ware. You might want to consider changing to Highwater's Little Loafers, which is a cone 6 clay that is comparable to Loafers Glory. At cone 6, Highwater states Little Loafers has an absorption rate of1.9%. That is a very acceptable absorption rate for functional work.

 

If you try the stain at cone 6 and it still fires brown, then you might need to either adjust (increase) the percentage stain or try it with other clear glazes to see if their might be a reaction between the stain and the glaze. Generally, the higher you fire, the greater the risk of some stain colors burning out.

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Guest JBaymore

There are ways to put glaze onto non-porous wares. Industry does it all the time. For example bone china is "bisqued" to vitrification and the then glazed low. But it is complicated more than most studio potters will want to tackle. mainly involves controlling the rheology of the glaze slurry. You also get into some fit adjustment.

 

Probably more trouble than other solutions.

 

You should be able to get a cone 6 body that is reasonably tight and strong for functional ware. You might have to make it tyourself. But don;t depend on a "cone 6 to 10" body. If it is good at 6 then it is overfired at 10. If it is good at 10 then is it underfired at 6. Pertty simple. It is probably really a cone 8 body.

 

Look at the docs on the particular stain you are trying to use. It should have a spec sheet about the desireable chemistry of the glaze it is added to for proper color development.

 

best,

 

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

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Dear John, thank you very, very much. That was extremely helpful and informative. Of course I would choose a design/color option that is so complicated, expensive, and nearly impossible to do--lol.

 

I'm going to get Rossol's book and check out the FDA regulations. Good to know this. And I'm going to continue to explore this stain/glaze, just to see if I can make it work... But not on functional ware.

 

In the meantime, I guess I'll find another glaze solution for this set of bisque dinnerware, and start over again with a cone 6 body and use a cadmium-free orange glaze!

 

John, can you recommend a cone 6 body (or formula) that is 'tight and strong', and preferably white, for functional ware? Are you familiar with Highwater's Little Loafers?

 

Thanks all for your help, it's a very interesting thread.

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There are CrAlFeZn and other orange/red/pink stains that contain no cadmium. Most of the dinner ware in these colors are made with some variation of chrome/tin, or chrome iron colorants instead of encapsulated cadmium. However because these are reliant on iron or chrome or both they will not be the same color in oxidation and reduction. They will also not always last up to cone 10, where as the cadmium stains are encapsulated in Zircon which has an extremely high melting temperature. The idea that cadmium stains can be safe relies upon the high melting point of the Zircon which encapsulates the cadmium.

 

Another thing to point out is that the FDA isn't an all encompassing governing body. Just because something is or isn't recognized as safe by the FDA does not mean it is or isn't safe. The only way to be sure is to submit test tiles to laboratory leach testing. I've seen many people using cadmium encapsulated glazes. These stains become unstable when put in a zinc glazes.

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Oh wow. So then do I understand correctly that cadmium colorants are not FDA approved for functional ware, even in encapsulated stains--despite Cerdec/Degussa's claims that they are food safe?

 

If so, how is that one can buy all sorts of red/orange ceramic dinnerware just about everywhere, from Walmart to Pier One? Are these manufactured dishes mostly likely low fire cadmium free colors?

 

Is there no way then to make orange, high fire, functional pottery?

 

 

Foster,

 

I have been teaching ceramic chemistry and toxicology for ceramic artists at he college level since sometime back in the 70's.

 

It is not that they are "not FDA approved", it is that if you use them in the USA there are specific FDA testing and recordkeeping standards that you must follow to comply with the law. That is what I was saying in the last posting. There are also limitations on the locations that cadmium bearing compounds can located be relative to the interior / exterior of certain pieces. These standards vary with the exact nature of the ware in question. So something like a cup is different from something like a pitcher, for example.

 

As to the commercial pottery manufacturers, they are in all likelyhood (hopefully) complying with the laws as specified. Large producers will have the resources to do this more easily than a studio artist. Otherwise they open themselves up to large fines....and also the potential of a product liability lawsuit in the case of documentable damages.

 

The FDA currently only regulates the leaching of two chemicals in ceramic glazes; lead and cadmium compounds. If you live or sell in California however, that state has regulations that are MORE stringent than the FDA laws.

 

It is not that you cannot produce this stuff safely. But the procedures necessary to REALIABLY assure that the wares are safe are more the province of industry, with tight glaze batching, glaze application, and sophisticated firing controls. Us stuudio potters tollerate variables that industry does not allow. Makes tight glaze control problematic.

 

Also the testing requirements will add costs to the production cost of the wares. Another reason it is more difficult for the small producer. You need to have a well structured regular sampling program that will assure that the fired wares are safe. This is going to cost you something. The testing will have to be by a lab....this is not "potter level chemistry" here.

 

Even if you make "non-functional" vessel type wares.... if the object could reasonably be used by a purchaser for food use, there are even specific labeling requirements that must be put on the ware in certain ways, and in certain sizes. Just having a hand tag that says "do not use for food" is by FAR not enough, nor legal.

 

Also the encapsulated stains are not necessarily unsafe. I am not saying that. They are supposed to do what they say they do. But the onus of responsibility for making sure that they DO that is on the producer of the end-use object. As in "YOU". The maker of the pot. The stain supplier does not indemnify the manufacturer (you again) that uses its products. They say it... but you are responsible for it by law.

 

Go to FDA.gov and start researching this stuff. Also get a copy of "Keeping Claywork Safe and Legal" by Mononna Rossol ...and sold by NCECA.

 

Too many studio potters do not know about this kind of stuff. Too few schools teach it.

 

Hope that helps.

 

best,

 

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

 

 

John, you say "As to the commercial pottery manufacturers, they are in all likelyhood (hopefully) complying with the laws as specified. Large producers will have the resources to do this more easily than a studio artist. Otherwise they open themselves up to large fines....and also the potential of a product liability lawsuit in the case of documentable damages." It brings to mind in the 70's the Fiesta ware situation. I remember after reading an article taking a geiger counter home to my parents and finding that all of their fiesta ware was mildly radioactive. There were other problems with their glazes at the time also. Another interesting situation was the way the Geiger counter reacted to the Amaco and other enamels in the jewelry studio at the HS. All of the yellows were hot! I know that the word out is that a little radioactivity is OK, but I think about wearing a pendant or eating out the a dish that is radioactive over the long term-Hmm gives me pause. We removed all of the radioactive materials that year and had them disposed of properly. Just a side in this discussion and the point that some of us out there are aware of the FDA standards, and their failings.

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Oh wow. So then do I understand correctly that cadmium colorants are not FDA approved for functional ware, even in encapsulated stains--despite Cerdec/Degussa's claims that they are food safe?

 

If so, how is that one can buy all sorts of red/orange ceramic dinnerware just about everywhere, from Walmart to Pier One? Are these manufactured dishes mostly likely low fire cadmium free colors?

 

Is there no way then to make orange, high fire, functional pottery?

 

 

Foster,

 

I have been teaching ceramic chemistry and toxicology for ceramic artists at he college level since sometime back in the 70's.

 

It is not that they are "not FDA approved", it is that if you use them in the USA there are specific FDA testing and recordkeeping standards that you must follow to comply with the law. That is what I was saying in the last posting. There are also limitations on the locations that cadmium bearing compounds can located be relative to the interior / exterior of certain pieces. These standards vary with the exact nature of the ware in question. So something like a cup is different from something like a pitcher, for example.

 

As to the commercial pottery manufacturers, they are in all likelyhood (hopefully) complying with the laws as specified. Large producers will have the resources to do this more easily than a studio artist. Otherwise they open themselves up to large fines....and also the potential of a product liability lawsuit in the case of documentable damages.

 

The FDA currently only regulates the leaching of two chemicals in ceramic glazes; lead and cadmium compounds. If you live or sell in California however, that state has regulations that are MORE stringent than the FDA laws.

 

It is not that you cannot produce this stuff safely. But the procedures necessary to REALIABLY assure that the wares are safe are more the province of industry, with tight glaze batching, glaze application, and sophisticated firing controls. Us stuudio potters tollerate variables that industry does not allow. Makes tight glaze control problematic.

 

Also the testing requirements will add costs to the production cost of the wares. Another reason it is more difficult for the small producer. You need to have a well structured regular sampling program that will assure that the fired wares are safe. This is going to cost you something. The testing will have to be by a lab....this is not "potter level chemistry" here.

 

Even if you make "non-functional" vessel type wares.... if the object could reasonably be used by a purchaser for food use, there are even specific labeling requirements that must be put on the ware in certain ways, and in certain sizes. Just having a hand tag that says "do not use for food" is by FAR not enough, nor legal.

 

Also the encapsulated stains are not necessarily unsafe. I am not saying that. They are supposed to do what they say they do. But the onus of responsibility for making sure that they DO that is on the producer of the end-use object. As in "YOU". The maker of the pot. The stain supplier does not indemnify the manufacturer (you again) that uses its products. They say it... but you are responsible for it by law.

 

Go to FDA.gov and start researching this stuff. Also get a copy of "Keeping Claywork Safe and Legal" by Mononna Rossol ...and sold by NCECA.

 

Too many studio potters do not know about this kind of stuff. Too few schools teach it.

 

Hope that helps.

 

best,

 

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

 

 

It brings to mind in the 70's the Fiesta ware situation. I remember after reading an article taking a geiger counter home to my parents and finding that all of their fiesta ware was mildly radioactive. There were other problems with their glazes at the time also. Another interesting situation was the way the Geiger counter reacted to the Amaco and other enamels in the jewelry studio at the HS. All of the yellows were hot! I know that the word out is that a little radioactivity is OK, but I think about wearing a pendant or eating out the a dish that is radioactive over the long term-Hmm gives me pause.

 

 

 

That is so crazy!! I never knew about that! I guess it'll make me think twice before purchasing that antique fiesta ware! LOL! ^_^

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I just wanted to add that if your Orange is always turning brown it is likely because of the clear glaze you are using, not the stain. I demonstrate this often to my students with a simple swatch of colored clay with several different clear glazes applied ... the change from glaze to glaze is often very obvious. The DeGussa orange stays orange right to Cone 10 with the proper glaze. The attached image shows the orange by itself and mixed with pink ... another color they say changes, but doesn't.

post-1585-131955846936_thumb.jpg

post-1585-131955846936_thumb.jpg

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Chris Campbell,

 

Do you have a recipe to share that has a demonstrated ability to hold color from these more finicky colors like orange and pink? Or a suggestion as to chemistry?

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Guest JBaymore

Yup Pres,... the radioactive thorium contaminant in the red and oange fiestaware is a well known "blip" in ceramic history. There are tons of older wares that are NOT all that great like that....... before people really were aware of this stuff.

 

Even today I am sure that ther is some stuff "slipping through the cracks" on the pubklished standards.

 

I know a number of potters who are using encapsulated stains with cadmium... and AFAIK are simply assuming that the stuff works as they are told by the supplier. But the law says the end user putting it in the wares has the onus of responsibility for a testing program.

 

best,

 

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

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Benhim

I do not make functional wares and seldom glaze so when I do glaze I use the Amaco zinc free clear glaze. It keeps the colors very true and i have not had any colors bleed.

 

 

I see, that's good to know. Thanks for the heads up.

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The reason why Cadmium or any other chemical might not be safe in a glaze is because of a eutectic temperature of combined materials. This is how glazes are formulated, there is a specific ratio of any two compounds that will cause them to melt at the lowest possible temperature, this is call the eutectic temperature. While it would seem like a colorant that's encapsulated in something like Zircon could not possibly melt out at pottery temperature, because Zircon doesn't melt out until 3974 F and doesn't even soften until about 2912 F. However that's the Zircon in it's pure form, when mixed with a colorant, and then mixed into a glaze the the new compound can form a new eutectic temperature much lower than the original glaze materials or the original colorant alone. Certain compounds will cause the Zircon to become unstable releasing the cadmium into the glaze where it can then be leached out into a person's food or drink. The only way to safely use toxic chemicals in functional ware is to have a firm grasp on the chemistry behind the glaze, and then back up your formulation with laboratory leach testing. However if your aim is to make non-functional ware, throw caution to the wind and have at it. The only concern at that point is to not poison yourself in the process of making the pots.

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Guest JBaymore

The reason why Cadmium or any other chemical might not be safe in a glaze is because of a eutectic temperature of combined materials. This is how glazes are formulated, there is a specific ratio of any two compounds that will cause them to melt at the lowest possible temperature, this is call the eutectic temperature.

 

It even goes way beyond this. Most real-world melts are "systems" composed of way more than two particular oxides. If you look at the typical phase equilibriam diagram, that is simply mapping out the nature of the melt involving three oxides... but the typical glaze interactions can go into far more complex combinations involving many oxides. It gets quite complicated. While a lot of research has been done on the behaviors of trinary systems,......... as you get into more combinations.... the available data pool starts to shrink.

 

You are right... this is why tesing of fired product is important when you are using something as toxic as cadmium compounds.

 

You are also depending here on the encapsulation process to be working in every batch of stain you purchase 100%. While I am SURE that good quality control is there at the manufacturing plant, as they say..... "to err is human". The PELs and TLVs for cadmium compounds are very low.... so in my opinion the precautions for handling raw glazes using these encapsulated stains should likely be pretty darn conservative.

 

best,

 

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

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