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Is my plate safe for food?

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Hello, this is my first time posting on here. My Mother in Law gave me a large plate about 17 inches in diameter. I’m sure she purchased it at a garage sale.  I’ve never used it and I’m in the process of cleaning/organizing my house. The plate is very nice but the bottom is not glazed. Does that automatically mean that it is not food safe?

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Im assuming when you mean bottom, you mean the underside of the plate, which sits on the table, NOT the bottom, meaning the area where your food sits.

Not at all. Glazes, during the firing, melt. If the bottom of the plate was  glazed and the bottom of the plate was touching the kiln shelf, it would be permanently affixed to the shelf as the molten glaze will bond the two together. Unglazed bottoms probably account for 85% or more (guessing on the percentage) of studio made pots which are totally food safe. There are ways to make work which will allow you to glaze the bottoms (not necessarily the foot) of your wares, and ways to glaze the entire vessel, but most do not.

However, if the clay was not fired to its proper temperature, and the clay is still porous, it can absorb moisture/soaps/bacteria which could be a food safety issue. Unless you know who made the pot, and could ask them, the only way to "test" its porosity is to do a couple of things. You can hold the plate from the underside with a couple of fingertips, and lighlty rap the edge of the plate with either your knuckle, or a wooden spoon. If you hear a nice "ring" the plate is well vitrified (not porous), if it has a hairline crack, or is un-vitrified it will sound like a broken drum head, or a muffled/dull noise.

You can also drop a drop-two of water on the unglazed portion of the plate. If the drops of water are immediately absorbed into the pot, the clay is unvitrified, however if they stay wet it is vitrified.

I was having a discussion just yesterday with another potter about earthenware pots, which have unglazed bottoms (and by their very nature are clays which CANT become vitrified) and are intended to be used in the dishwasher, microwave etc. She felt it was fine, I disagree....not ok. Maybe someone with more definitive proof can chime in on this, but even if the clay is not vitrified it may still be fine to use. My opinion, is if the clay isnt vitrified, its not ok to use for food.

Post a photo or two of the plate which may help in deciphering its "usability"

Edited by hitchmss

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Wow, thank you soooo much for your very detailed response! I sincerely appreciate it! I will do a test with the water drops. I tried to include an image but my file was too large. Now that you mention it, it does look very similar to some earthenware designs. 

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