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determining target specific gravity for glazes

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thanks, beebop for posing the question and Min and Callie for their explanations.   if i understand correctly, using specific gravity is a reliable way to repeat glazes and should be part of the original test of a recipe.    just in case the recipe and clay and firing work well together or look just interesting enough in the testing phase to be close to perfect.   knowing the SP allows for incremental additions to reach that perfect state.   since the test for SP is simple, you may as well do it.

thanks to all for your contribution.   not promising to do this because i still have questions that i do not want to confuse this thread.



Edited by oldlady
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It’s kind of like adding salt to a recipe. It’s a to-taste measurement based on your own circumstances, and what you prefer. Like a recipe in a cookbook, any suggestions about its use should be considered a starting point, not a hard rule.

 SG measurement is something to take note of for consistency, but the number you wind up using is for your own benefit, and might not be useful to someone else. 

@oldlady if you have questions, you know you can start your own thread! We are happy to nerd out for you.

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Glazing has been much more fun for me since learning to: screen out lumps; to stir thoroughly and as frequently as required; consider specific gravity and thixotropy; take notes and leverage same. From there, building some skill, that is, glazing a few hundred pots -> a lot less mess, more nice even coatings, much less dripping and sheeting. Perhaps, given many thousand more pots, one could become proficient?

I'm sticking with specific gravity and thixotropy being companion topics, like, uhm, perhaps yeast and sugar in baking; the yeast creates the bubbles, however, no bubbles without sugar.

How to measure thixotropy, per prior, I have my method, which echoes Mr. Hansen's observation in his video on the subject. Try  stirring your glazes, then observe the mass of revolving glaze as it slows to a stop; compare to Mr. Hansen's - after the adjustment - in his video.

This thread (or similar thread) was mentioned, above

Flocculation and specific gravity - Clay and Glaze Chemistry - Ceramic Arts Daily Community

I use a kitchen whisk - modified to chuck up to my (new lightweight DeWalt!) cordless - to thoroughly stir glazes, and a long square cornered scraper to get the sides and bottom corner. From there, a large hand whisk, periodically, for that bit of watery at the top o' th' bucket. If I happen to run across a powered mixing stand - a lab mixer - or something like it, cheap, I'd snap it up, on account o' with enough power and time, screening could be eliminated, as several others have pointed out (in other threads).

Glaze on!


Edited by Hulk
watery, where?
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No matter if I'm mixing a glaze from scratch or mixing up a wet 5 gallon bucket or a 30 gallon bucket-I aways use a 1/2 inch drill with a large jiffy mixer in drill (smaller cordless drill and jiffy mixers for smaller containers ) I have two cordless with smaller jiffy heads on them in glaze room as well as the larger 30 inch shaft large head jiffy. All the drills are dedicated glaze room drills and ready to go when needed.

I mix up the glaze and either use my hand or weigh it in syringe or just look at it with a stick (I have a stick in each bucket after mixing glazes to stir during the glaze day.-I do all 15 buckets every glaze day (I mix the needed glazes the day before glaze day so they are ready)

I make sure all glaze is off the bottom with jiffy mixer before checking SG with hand or looking or measuring.

same routine past 4 deacades works for me

The power jiffy head and drill  mixer gets the job done better than a wisk or a toilet brush or your kitchenaid mixeror a stick alone.

Edited by Mark C.
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mark, i have that really big jiffy mixer and use it.  

just for chuckles i will tell you about the day i tried to mix a big batch in a 5 gallon bucket.  i had just mixed the ingredients and added water.  the bucket was holding 10,000 grams of solids.  when i turned on the jiffy mixer, nothing happened,  i squeezed the trigger on my heavy drill and suddenly the entire bucket began to revolve around the stationary drill.    memory loss has blessedly removed the later details, all i can recall is the visual vortex and deciding to never do that again.  like looking down at a tornado from above.

another reason to wait until freshly wet ingredients have time to absorb the water before stirring.

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