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Specific Gravity For Glaze


ronfire

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Some how my math does not add up.

 

A little history first.  I mixed up some clear cone 6 glaze and thought it was to thin so I added about 25% or more premix dry glaze then thickened slightly with epson salt and have been using it for a while but am now getting runs.

 

So it thought I would dilute the glaze to the proper specific gravity. I zeroed the scale with a container and weighed in 100 grams of water and marked the vile. So to get my glaze SG fill to the same volume  and then the glaze should weigh 145 grams  for a SG of 1.45  right?

 

The surprise is that even though I mixed the glaze with less water than called for it will weigh in at 140 grams.

 

Does the specific gravity change as you use the gaze, as in the water ratio increases as you use it. I expected the glaze to get higher specific gravity as you use it.

 

I was planning on fixing this glaze tonight so I can fire it in the morning no I am puzzled.

 

 

 

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I think it depends what kind of container you are using to measure. If it is say a 500ml jug it would be easy to add those extra few ml of glaze or leave them out. I use a 50ml syringe and double my weight. Cheap and readily available.

 

What is the specific gravity of the original thin mix? Have you measured that.

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I am probably mistaken, but it seems to me that so many asking about sg don't seem to understand that it is different for every glaze and how each potter likes the way it looks on his or her clay. One potter may like a certain glaze a bit on the thick side for his clay and another might like the way  the same glaze looks quite thin on her clay.  They will find a sg that works for them

There is no hard and fast rule for what each glaze should be--I have changed the sg on some of my glazes when I have changed the clays I use...please correct me if I am wrong or if I have not expressed this right. Also remember to keep your liquid measurements very accurate...sometimes just a few grams can make a difference.

ginny

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