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synj00

Hydrometer - Trying To Get The Hang Of This!

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I'm trying to get the hang of using my Amaco hydrometer to get consistent specific gravity with my new glaze tests and also with my slip. I cant learn anything if I just keep guessing. I want consistency when it comes to "my" part and then after that the fire gets to have its say.

 

So in glazing I get information that says glaze should be around 140 to 160 sp gr but the readings are for 1.xxx. On this scale 1.00 is even with water, nothing in it. Or on the other side it is 0-70, 0 being the reading for water.

 

Here is a pic of what I think is the proper consistency of a Leach Temmoku glaze. It reads 1.600. I know that there are deviations depending on what type of glaze and that some need to be thicker than others but looking for a starting point really.

 

image2.jpg?w=720

 

In the Britt high fire glaze book there is no specific gravity except for some recipes that I guess are deviations from a standard? Does anyone know the standard specific gravity for this particular book?

image1.jpg?w=720

 

Also on the same topic when using slip for dipping and general purpose decoration like brushing what should the general specific gravity be? I seriously need to get a real drill that can mix a 5 gallon bucket of slip. Its hard doing it with a kitchen whisk ;-)

 

Hoping the answers I get will help others along the way! Thanks everyone for your input!

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So in glazing I get information that says glaze should be around 140 to 160 sp gr but the readings are for 1.xxx.

 

I think that somebody has lost a decimal point from the 140 & 160 figures. [*]

As a point of reference the sg of lead is 11.35, so figures over a hundred are definitely unrealistic.

The 1.xxx figures do sound like sg readings.

 

http://digitalfire.com/4sight/glossary/glossary_specific_gravity.html

Glazes do not have a universally desirable specific gravity range like casting slips. The same glaze can be used effectively by different people and in different processes having quite different specific gravities. We have seen glazes with a specific gravity approaching 1.7, others at less than 1.4. This is not only due to the difference in glaze materials and the way they suspend and interact in the slurry, but it is also common for people to add flocculants and deflocculants to glazes. Here is an example of the instructions for one commercial glaze sold as a powder:

 

The 0-70 scale sounds like it might be measuring in degrees Baume.

e.g. see https://www.aardvarkclay.com/products.php?cat=398

Degrees Twaddle is another relic from the past you sometimes see used, especially for sodium silicate.

 

Regards, Peter

 

* Of course if somebody is writing down (or calling out)  lots of figures in the 1.xx range

they may find it easier and less error-prone to leave the decimal point as implied.

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I use that same scale every week-the readings are in the range of 1600-1400-just drop the zero.

as to the drill a harbor frieght 1/2 inch drill is cheap and will hold a 1/2 shaft for a 5 gallon jiffy mixer.

Mark

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Guest JBaymore

As Tony Hansen points out in the quote above...... Specific Gravity is only one part of the picture relative to application.

 

Something that gives you more information about application qualities is the Viscosity.  You can get a "viscometer" but they are expensive.  A suitable "potter level " of technology is the #2 Zahn Cup. 

 

You can MAKE a homebrew "Zahn Cup" yourself with a small can with a drilled hole in it.  You time the given amount of material exiting the cup with a stopwatch.  It is not accurate to communicate the values to others... but for your own work...... it is accurate enough.  Once you know the value you like for your application methods (dip, pour, spray, etc) and quality of bisque (or greenware) you are applying it to...... just use that number for your own use.

 

best,

 

.......................john

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Thanks for the tips everyone. Will play some more. A drill is coming home with me tonight whether it likes it or not. Playing more with my local lake clay / slip getting ready for a high fire. :D

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