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Pit fired/unglazed clay "can't hold liquid"?

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My family and I've been making pottery lately and having a lot of fun with it, I'm getting ready to fire them and although I've read a lot of stuff about pit fired clay not being "food safe" (I'm not concerned, and they're only for our personal use) but I just read that they can't hold liquid, that it will go through the cup/vase/teapot/whatever. Is that true? 

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Pit fired clay won't be vitreous or mature, which for these purposes means that the clay will be porous.  Pit fire temperatures just don't get hot enough.  Pieces made this way will definitely seep over time. I wouldn't, for instance, leave a beverage standing in a cup for very long. It would be very difficult to keep clean, impossible for it not to stain with food use, and it won't be terribly durable for the kind of abuse that a piece might see in a regular kitchen. It's not really practical. But it does make some really beautiful decorative work. 

Edited by Callie Beller Diesel

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Pit firing is a blast....but, depending on your location, you may want to think about your surroundings.  I did my first pit firing (as an adult ) in my urban apartment complex's small common wooded area. I was told that was not a welcomed activity, per several neighbors. Something about the smoke and fears of fire.  The pieces came out great, tho!  

One other thing--if you leave pit fired wares outdoors in freezing temps, they may end up cracking from the freeze/thaw stress, as pit firing will not enable the clay to withstand thermal shock.

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On 3/20/2018 at 4:29 PM, LeeU said:

Pit firing is a blast....but, depending on your location, you may want to think about your surroundings.  I did my first pit firing (as an adult ) in my urban apartment complex's small common wooded area. I was told that was not a welcomed activity, per several neighbors. Something about the smoke and fears of fire.  The pieces came out great, tho!  

One other thing--if you leave pit fired wares outdoors in freezing temps, they may end up cracking from the freeze/thaw stress, as pit firing will not enable the clay to withstand thermal shock.

 

We live on a 11 acre off grid property and we make fires quite often, to make charcoal, to cook in our fire pit (which is where the pottery was made) and to dispose of things that can't be composted etc. so that won't be a problem. I couldn't imagine living in the sort of setting you describe, seems really restrictive.

 

We went through with the firing, we used a mixture of activated charcoal, salt, manure from the horses and the sheep and iron oxide that had collected under my sander from years of sanding rust off of things. Turned out real nice but they did weep water a little bit, the solution we used was shellac (the pure stuff that comes from a lac bug, not synthetic stuff) which is apparently perfectly food safe as long as the medium used to dissolve it is pure ethanol and not methylated spirits, we added 3 coats to the inside of each vessel, one coat all around the outsides (to avoid them getting too shiny) and another three coats to the bottom, shellac is water resistant not water tight, but one coat can hold back water for 4 hours, so I think they should be fine for nearly everything, I'm drinking tea out of one of the cups right now without any leaking, even less so than my store bought cups which leave little water rings.

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Shellac is made from beetles but need Ethanol to dissolve it to get it in a liquid state. This Ethanol can be natural (from sugars or petrol chemical) in make up. That will make it less food safe. How do you know what your ethanol source is?

Since this really is a wax it will not hold water for long amounts of time but it sounds like you do not care (only for drinking a cup worth)

The thing about super low temp fires wares ,whether dung or charcoal fired is the just do not have longevity to them.Sounds like that part is ok for you.

My pit fired stuff is long ago broken and gone.

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