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Some Questions About Lidded Jars


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If I want a glazed jar that finishes at 16oz how do I know if the inside is the right size when I'm throwing and before it shrinks after firing?

 

Sure I can take 20oz of clay and depending on the wall thickness I can get various sizes. Is this something I just need to learn to visualize or is there a tried and true method to figure this out?

 

(Maybe a 16oz mug really holds more than 16oz?)

 

french butter dishes, boxes, lidded jars etc are all fired as a closed unit.

 

So I don't glaze where the rim and lid touch, leave a little space in case of a drip or two and I will be ok?

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re the question on fired volume relative to wet volume for mugs:

If you know your percent shrinkage for your clay body, you can estimate the volume shrinkage for a mug by using three times the linear shrinkage.  ie, if your mug made from a lump of clay holds 100 cc when wet and the shrinkage is 10 pct for that clay body, then you mug will hold about 70 cc after it is fired. 

[There are some second and third order terms that could be considered, including the phase of the moon and how many grapes you had for breakfast last friday, but they are all quite small.]
 

LT

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I happen to love making lidded jars!

This guy started as 1.5 lbs of clay for the body, and I couldn't tell you how much for the lid because I throw them upside down off the hump. It holds 18 fl oz. That gives you a starting point, and yes, you're going to have to play with the amount of clay yourself, because your clay will fire differently/may have different moisture content and density, our skill levels likely differ, etc. Etc etc.

 

 

I fire my lids on the pot whenever possible. I wax the inside of the gallery and the rim of the lid, and scrupulously clean any glaze residue out of the whole gallery area so they don't stick to each other. Having made so very many lidded items in my life, I think the most common hazard is glazing the lid to the pot, followed by having the pot rim warp inwards too much, and trapping the lid. Take your flange measurements as accurately as you can, and fit the lid and the jar together at the earliest possible moment. Also, each clay will behave a bit differently, so you really have to pay attention to your pots as they dry, to see how the two pieces change together and in relation to one another.

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re the question on fired volume relative to wet volume for mugs:

If you know your percent shrinkage for your clay body, you can estimate the volume shrinkage for a mug by using three times the linear shrinkage.  ie, if your mug made from a lump of clay holds 100 cc when wet and the shrinkage is 10 pct for that clay body, then you mug will hold about 70 cc after it is fired. 

 

I can wrap my head around that

 

514cc (17.38oz) wet

13% shrinkage x 3 = 39

514cc - 39 = 475 (16oz) dry

 

Thanks LT

 

====

 

Lovely jar Callie.

 

Looks like you don't glaze under the lid.

 

I've been throwing my lids right side up then trimming the inside while it sits in the jar upside down. I'm going to try it your way next time and see how it goes.

Thanks

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