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missholly

how to measure glaze consistency

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missholly    1

im trying to find the little cup you dip in that has a hole in the bottom and you time how long it

takes to drain. anyone know what thats called?

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Denice    243

I just bought a plastic measuring cup and drilled a small hole in the center of the bottom. I put my finger over the hole and dip it and fill it to 8 ounces, then I time it with a clock with a second hand so I can record the exact time. If that thickness like a minute and 3 seconds looks right I will dip a test tile, fire it and check the results. If I'm happy with it I'll add the time to the glaze formula so the next time I make it or just need to thin it I have the exact time. Denice

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missholly    1

mark, that is exactly what i was looking for. thank you!

i had seen it once in a video and just didnt know what to call it.

and thanks for the other ideas, guys.

 

is there any kind of database that shows a suggested consistency on different glazes such as brushing/spraying/dipping?

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John255    6

 

is there any kind of database that shows a suggested consistency on different glazes such as brushing/spraying/dipping?

Miss Holly,

As potters we swim in a sea of variables.  The database numbers you are asking for probably don't exist because each glaze formula requires different amount of water.  Most suppliers recommend for one pound of powered  glaze use slightly less than one pound of water.  Some say a specific gravity of 1.45~1.50.

 

What is probably more effective for your clay and bisque is to calibrate yourself.

Make up a batch using one of the above methods then dip a small bisqued cup in the glaze for a count of three then when the glaze looses its shine scratch it with a pin tool to see how thick the glaze is.  If it is more than about 1/16" scrape the glaze off and add more water.  If it is barely about 1/32" let the glaze batch settle overnight then siphon off some water from the glaze.  If you do this several times you will know when you have the right mix just by looking at the way the glaze drips off the piece, or drips off your fingers.  Most (not all) of my glazes need two~three drops to be right.

Make adjustments to the above by looking at the fired pieces.  And try to remember to make notes.  

Good luck.  

John255

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Mark C.    1,802

I use the cup for measuring slip and a hydrometer for glazes-its all what you learn with to repeat again with same results.

I first learned what the glaze did as it ran off my hand in bucket which I can still do but since I wear latex gloves the past 15+ years I choose to use the hydrometer with scale marks on it-just remember not to use a slip hyrometer as thats a different scale..

This post may help for small amounts as well-

http://ceramicartsdaily.org/community/topic/2787-hydrometer-use-with-small-amounts-of-glaze/?p=22067&fromsearch=1

Mark

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Ben    7

You are talking about a viscosity cup and as mentioned, viscosity and specific gravity are different and independent. You must regulate both to control how a glaze applies.

Specific gravity is most accurately measured using a gram scale. Balance the scale with an empty, dry 100ml or 1000ml graduated cylinder on it. These are available online for very little money.

Fill with well mixed glaze to either 100 ml or 1000ml and weigh. Water weighs 100 grams per 100ml. If the sample in the 100ml test weighs 127 grams the smaple has a specific gravity of 1.27.

 

The viscosity of the glaze can be affected by numerous factors and is measured by dipping the cup in and timing the time it takes to drain. 

How to adjust viscosity will be determined by the ingredients in the glaze.

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