Let's Talk About The Term "Food Safe" In Glazes, Pottery & Ceramics
First I'd like to say do your own research on the matter of "food safe" here are the two links that pertain to glaze food safety. It's always possible that I missed something, if you see I did politely reach out, any helpful info is always appreciated.
https://www.fda.gov/media/71762/download https://www.fda.gov/media/71764/download
What does "Food Safe" mean for glazes in the USA?
First let's understand the term "Leaching"
Leaching: When an acidic liquid sits in a vessel. It can have the tendencies to pull particles from the glaze into the liquid. Then if the liquid is consumed you are ingesting the leached particles.
Next lets understand what a "Glaze" is
Glaze: Is a glass formula tuned to melt and fuse onto clay at certain temperatures.
A few key things to note here,
- Temperature
- Clay Body
I'm aware of this because I do my own lab testing you can have a different result if the temperatures are not the same. Also the clay body that is under the glaze can change the results of a lab test too. Example, a brown clay body could contain manganese dioxide, a porcelain clay body would not. So if you lab test with a brown clay body, you could have some magnesium dioxide come up on a lab test. On the other hand the porcelain clay body would show no signs of manganese dioxide.
When I send out a sample to be lab tested I always keep a witness cone next to the piece and I note the kiln make and model, and the firing program that was used for the firing. Another thing to note is how new/used are the elements, and kiln components. A faulty thermocouple could cause a kiln to fire a little hotter than it should. In this case that wouldn't hurt the results, but under firing would. If your kiln registered an error code and did not make temp in a glaze fire. This would be an issue if the glazes were not melted properly.
According to the FDA guide lines your glaze for Cadmium is
Flatware Average of 6 units 0.5 micrograms/ml
Small Hollowware any one of 6 units 0.5 micrograms/ml
Large Hollowware any one of 6 units 0.25 micrograms/ml
According to the FDA guide lines your glaze for Lead is
Flatware average of 6 units 3.0 micrograms/ml
Small Hollowware other than cups and mugs any one of 6 units 2.0 micrograms/ml
Cups/mugs any one of 6 units 0.5 micrograms/ml
Large Hollowware other than pitchers any one of 6 units 1.0 micrograms/ml
Pitchers any one of 6 units 0.5 micrograms/ml
So with that being said here at theglazekitchen when I'm doing my lab testing not only do I test for the required lead & cadmium, I also test for every colorant that I have in the glaze then I follow drinking water regulations to determine if it is "safe" or not. If my glaze recipe is outside of the drinking water regulations I will NOT say it's food safe. If I wouldn't use it for myself or my kids I will NOT sell it to anyone else. I want you as a customer to be well aware of that :)
Thank you for considering any of my products I put a lot of time and effort into making them the best I can. I can't wait to see how this grows in the coming years. Thank you <3