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What Exactly Do I Have Tested For Leaching On My Food Ware?


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#1 pottersc555

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Posted 21 July 2014 - 07:55 PM

greetings!

i know this topic has been talked about exhaustively.  (i'm ducking as i type this).  i have read thru tons of threads on past questions on the topic food safe glazes.  so greatful i found this site and all of it's info.  after reading numerous threads and thoughts and opinions i have decided to get my commercial glazes tested at brandywine.....just can't figure out WHAT to get tested since i use lead and cadmium free glazes.  

 

i use 4 standard commercial glazes.  i bought my TNF kiln brand new and have never used glazes with lead or cadmium.  i fire consistently the same.  i contacted the manufacturers today to figure out WHAT i should test for and can't seem to get a good answer.  they are protective of their recipes (which i understand) but i am having a hard time getting some direction on what might be in their glaze that i should get tested. 

 

wanted to see if anyone is familiar with these following commercial glazes and what your thoughts are on WHAT i should have tested.  i read one thread of a savvy potter who KNEW there was lead in a glaze (manufacturer kept saying there was no lead in it) he bought but it took several calls to get someone at the manufacturer who actually KNEW there were trace amounts of lead in it. 

 

so does it make sense to just have the labs test for lead on each piece? is there any logic to that? these are the following i use:

 

coyote cone 6 blue oasis-was going to have them test for copper leaching

coyote cone 6 cobalt blue-was going to have them test for cobalt

coyote cone 6 shino--no clue what to have them test for. hoping someone else uses this glaze and can give me some direction.

coyote cone 6 black--no clue what i should test for.  waiting for manufacturer to get back to me.  (i use this to layer under shino...looks awesome but not sure if it would be food safe.  one site says once you start layering glazes "all bets are off.") so i was going to send a layered piece in for testing but same question--what do i have them test for?

amaco cone 5/6 tourmaline--no clue what i should test for.  have traded emails back and forth but can't get any ingredient in this that i SHOULD test for.

 

again---just trying to be responsible.  don't want to blindly trust the manufacturer since i am the one making the product. plus i like the idea of having documentation saying that i have taken that extra step.  

 

any thoughts to those who have had commercial glazes tested? i tend to think way too much and make things much harder than they need to be---did you just have them test for cadmium and lead leaching since those are the only ones regulated by the FDA? is there any point to having any of these tested for cadmium since i don't use reds? or did you have any other specific ones tested for leaching?

OR any questions specifically i should ask the manufacturer since they are pretty careful about what they say is in these glazes?

 

eventually i will maybe start mixing my own glazes...i am nowhere near that stage right now.  hoping to stick with these 5 commercial glazes while i concentrate on form and body of my pieces. 

 

if you are still reading--much appreciated.

trying to figure out the most logical way to go about this. 

 

regards,

rachael



#2 JBaymore

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Posted 21 July 2014 - 08:43 PM

At the minimum get the MSDS for the particular glaze.  From that you MIGHT be able to tell what is in it... if not the amounts.

 

Only test for things that can be toxic and that are (or might be) there.  No need to test for stuff like SiO2, Al2O3, etc.

 

best,

 

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

 

See the FAQ at the top of the Technical For um section if you haven't already.


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

http://www.JohnBaymore.com

#3 pottersc555

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Posted 21 July 2014 - 09:06 PM

john,

thanks for the response.  this is the MSDS for all of their glazes. looking thru to see what i should get tested for.  also looking thru the links in the FAQ.  thanks for the direction. 

 

http://coyoteclay.co...lazes (wet).htm



#4 Bob Coyle

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Posted 23 July 2014 - 10:37 AM

There is no mention of lead and there is a disclaimer at the end of the MSDS that cadmium might be present. The amounts of documented potentially toxic metal salts are pretty much in the range of what most people use in glazes that are "food safe". I don't think you need to test for anything, but if you are concerned then have them tested test for cadmium leaching. That is the only heavy metal salt that is questionable in the analysis.

 

As I have said before, the end use of the containers you make has a lot to do with how safe a glaze is for "food use". You could probably get away with using some pretty nasty lead oxide glazes for something like a serving platter but watch out if you use them for an lemonade container. For a glaze component to leach, it has to be in contact with a substance that chemically reacts with the glaze. Even if some leaching of metals does occur, it generally is well below what is normally considered a harmful level. Many times the level of the same metal salts is higher in the drinking water that comes into your house.






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