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Encapsulated Cadmium


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#1 Min

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Posted 14 March 2013 - 04:21 PM

Question for the chemists / glaze guru's concerning the effect of spraying underglazes, glazes or slips containing zircon encapsulated cadmium. I seem to remember reading somewhere that mechanical treatment of encapsulated stains, (spraying or ball milling) breaks down the encapsulation thus rendering the cadmium free to disperse in the glaze. Am I correct in this or is it possible to spray encapsulated cadmium materials and not have the break down? There seems to be a lot of potters spraying the new bright underglazes that contain cadmium.

Second part to the question, does anyone have knowledge of why Speedball doesn't list cadmium as a hazardous material? I contacted the chemist at Speedball and inquired which of their underglazes contained cadmium, this info is not listed on their MSDS. I was told there are 8 underglazes containing cadmium, all colours have "None" listed on the MSDS for Hazardous Ingredients. (Spectrum and Crysanthos list their underglazes containing cadmium)

Min

#2 JBaymore

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Posted 16 March 2013 - 01:33 PM

Question for the chemists / glaze guru's concerning the effect of spraying underglazes, glazes or slips containing zircon encapsulated cadmium. I seem to remember reading somewhere that mechanical treatment of encapsulated stains, (spraying or ball milling) breaks down the encapsulation thus rendering the cadmium free to disperse in the glaze. Am I correct in this or is it possible to spray encapsulated cadmium materials and not have the break down? There seems to be a lot of potters spraying the new bright underglazes that contain cadmium.


Ball milling certainly is not something you should do with these inclusuion stains. That serious level of grinding of the particles will screw up the structure of the particles and likely change release factors.

I'd not heard that issue about spraying. I suppose high velocity contact betwen the material in the stream and the metal of the nozzle COULD cause some abrasion of the particles.... but logic says to me it likely is not going to be an issue because it is so minimal. But I could be WAY wrong on that one. I'd contact the suppliers directly about this question. And please post what you find out here for all of us to see.

Personally..... even using encapsulated versions... I'd never spray this cadmium bearing stuff. You are literally trusting your life to the stain manufacturer's quality control program and the quality of your local pickup ventialtion system and respirator filter and fit. Cadmium is bad stuff.

Second part to the question, does anyone have knowledge of why Speedball doesn't list cadmium as a hazardous material? I contacted the chemist at Speedball and inquired which of their underglazes contained cadmium, this info is not listed on their MSDS. I was told there are 8 underglazes containing cadmium, all colours have "None" listed on the MSDS for Hazardous Ingredients. (Spectrum and Crysanthos list their underglazes containing cadmium)


For proprietary products like glaze, slip, underglaze, overglaze, luster, and the like, MSDSs are really only a START in trying to understand "what is in there". One BIG issue is that no one is really regulating the accuracy of the MSDSs prepared by the companies. So the company iteslf puts together the form with whatever ihnformation they decide to include. I've seen some MSDSs that are clearly a joke.

I have not looked at the particular sheets in question..... but sometimes they make up the sheet for the BASE glaze/underglaze, and so on... and then the colorants are not listed on the "main" product form. Tricky way to "hide" things that they don't want to draw any attention toward.

Also some things can be "technically" listed as non-toxic ingredients.... because thay are being looked at as WET. Take SiO2..... known human carcinogen. It is in every clay body, every glaze, and so on. When it is DRY and gets airborne....... it is highly toxic. Wet....... it is not.....because it can;t get airborne. (Hence the "Certified non-toxic" labels plastered all over most wet clay boxes.)

So........ that is probably how they do that.


FYI ........ Once I had a significant health issue that my doctors decided was related to exposure to a specific art material I was using in ceramics. Commercial product with a oil based carrier. I tried to contact the supplier to get the details on what was in there. Neither my doctors nor I could get the information we needed no matter how hard we tried. It would have taken a bevy of layers and likely a court trial to get any specific answers. The MSDS used a generic term for the carrier content and they fell back on the "prioprietary secret" business.

Caveat Emptor!

best,

.....................john
John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#3 JBaymore

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Posted 16 March 2013 - 01:38 PM

OK... for yucks I went and looked at Speedballs's MSDS for their underglaze.

Remember I mentioned above I'd seen some MSDSs that were a joke?

I'm going to see if I can get Monona Rossol to comment on this one.

best,

.......................john
John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#4 Min

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Posted 16 March 2013 - 05:27 PM

Hi John,

Thanks for taking the time to reply. I'll contact a few suppliers and see what they say. To many potters out there using what appear to be unsafe glazes, high copper mat glazes on food surfaces etc that are unsafe so I would like to have some knowledge regarding inclusion Cd materials as I see this as being the next area of concern.

Min

#5 Min

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Posted 15 April 2013 - 09:53 PM

Thought I would post the replies I received from Mason Stains re CdSeS stains and their integrity after spraying.

Two people from Mason replied to my question re CdSeS inclusion stains and their integrity if applied by spraying. From their emails to me: "The encapsulated stains will not break down on spraying. The stains should not be milled for more than 15 minutes, but I am assumimg that you do not mill your glazes in any case. It is safe to spray, dip or handle in any normal manner." from George Vardy who is retired from Mason now but was kind enough to answer my question.

The other email "We spray a lot of pieces here at Mason Color and the spraying does not break down the integrity of the pigment. The only way we have found to ruin the encapsulation of the pigment is to ball mill the pigment for a lengthy amount of time. As for the leaching question, we really have no information on that because a lot the leaching has to do with how the
customers are using the pigments. How they are glazed, fired, put into slips or bodies. The leaching deals more with the application.

I also feel that spraying can be as safe of a technique as any as long as it is done with the proper precautions, and like I mentioned early that is how we apply it here in our QC work and it works very well.

Thanks and I hope this helps,"
Vince Wright
Mason Color

Encapsulated, sintered, washed, it's still a material I'm not convinced I should be spraying as a zero dust situation is hard to maintain on a constant basis.
Min

#6 yedrow

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Posted 18 April 2013 - 10:41 PM

This just occurred so I'm going to toss it out there: What happens if an encapsulated cadmium bearing glaze/slip runs on a kiln shelf and you grind it?

Joel.




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