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Jennifer Harnetty

Residual Lead In Kilns

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A reader sent this question about residual lead in kilns...

I understand lead, when fired, gives off vapor and what not that effectively settles into a kiln making it unsuitable for use in firing functional ware. Is there any way to test a kiln for this? I have been looking for used kilns but many people are unaware of exactly what might have been fired in them. If lead is in the kiln is there a way to remove the lead, seal it or do something to the kiln as to make it usable again for food ware?

 

Also, do other toxic materials such as Barium and Cadmium result in the same leaching and adhering to a kiln causing it to potentially pass into other ceramics meant for food? Thank you for your time and help!

 

Can anyone weigh in?

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Guest Bill Jones   
Guest Bill Jones

I'm not sure what it would take for lead to become vapor in a kiln (its boiling point is 1470 C), but one could use a lead test kit (the same kind that's available for testing paint) to see if a kiln is contaminated with lead. If it is, there is nothing I know of that will mitigate it. My suggestion would be to take the lead test kit along and test the kiln before purchasing.

 

The only way to actually test for whether or not lead would make it into your ware is to fire the kiln with a glaze that contains no lead or cadmium or any other material you don't want. Then have that same ware leach tested by a lab for each material you are concerned about. You would need to make the test vessels to the lab's specifications.

 

 

It is probably best to test the kiln before you buy it with a lead test kit, as Sherman suggested. But you can get rid of lead in a kiln by firing a container of nepheline syenite to absorb it. The container can be made of clay and should be about as big as the inside of the kiln. Put Nepheline Syenite into the container and then fire 270 degrees (F) per hour to 2000 degrees F. Hold for two hours. After firing dispose of the Neph Sy properly. This process doesn't guarantee that all of the lead will be absorbed so you should still have your ware leach tested by a lab!

Here is a list of people who provide these services:

http://www.digitalfire.com/services/consultants/index.php

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Carl    0

Just as a follow up question to the suggestion to have your ware leach tested by a lab, does anyone have an idea (in general) about how much it costs to have that done? Was curious to know if it is generally in the $100's, $1,000's or even higher. Thanks!

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earthartam    0

Well this is a rather disturbing thread! How many potters out there, professional or hobbyists, have bought their kilns used, never considering that it may have been previously used for god-knows-what purpose with god-knows-what chemicals? I have been using my ancient second-hand kiln for 15 years, and have put countless vessels out into the world, never even imagining there could be a problem with passing on lead poisoning to myself or others! sheesh! Is this really that big a threat to health and safety?? Perhaps all kilns should come with labels explaining the risks that previous users might possibly be causing. Do I need to get shopping for a new kiln, post haste?

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