Ivor J.Townshend on fri 20 aug 99
Hi!
I'm a mature student (dare I say old student) half way through a two
year Ceramic Design course at our local College here in the UK. I
have been following the discussion of Specific Gravity and Density,
but have a problem of my own.
My hydrometer is scaled from 40 to 60 degrees Baume not in grams per
millilitre or the specific gravity ratio. I would like to know what
the relationship is between Baume and Specific Gravity.
I have managed to find from a winemaking source a rule for
converting Baume to Potential Alcohol. From a separate source I have
a rule for converting Specific Gravity to Potential Alcohol. By
combining them, I come up with the rule for converting Baume to
Specific Gravity. This is
Take the Baume multiply by seventy four and divide by ten thousand
and then add one. Forty degrees Baume comes out at 1.29 and sixty
Baume comes out at 1.44.
These are a little low for Tom Buck's suggested densities for glaze.
However, and this is the critical bit, if my two authors use different
rules for potential alcohol then their rules cannot be combined in
this way and the results are garbage.
Help!
Does anyone have a reliable rule for converting Baume to Specific
Gravity? Can they also give me a reference to justify it?
I could always use the hydrometer just to bring the glaze back to a
constant gravity but I would really like to know what that gravity
actually is in terms of Specific Gravity.
Any help or guidance would be much appreciated
Ivor
(In Macclesfield, just up the road from Josiah Wedgwood's original
pottery)
Bill Aycock on sat 21 aug 99
Believe it or not- I have fun with these conversions- I will give the
conversion- but- please read the caveat at the bottom.
The equation is: Sp.Gr. = m divided by the quantity (m-d), where:
m= 145 in the US, was =144 in an older scale used in Holland, and = 146.78
in a new scale called the Gerlach scale.
d= the Baume reading.
The reference is the Handbook of Chemistry and Physics, (also called the
Chemical Rubber Handbook)- I looked first in the oldest issue I have, the
31st edition, 1949.
The caveat is: PLEASE- do not ever use a hygrometer to measure the specific
gravity of a slip or glaze. For Terra Sig, its ok, but for higher specific
gravity stuff- no.
I did some experiments (reported here on Clayart) and proved to myself that
I could get readings that varied by LARGE values, this way.
The prefered way is to get a small container (about a half cup will do) and
weigh the container when it is brim full of slip or glaze- then, clean the
container and weigh it with water to the same level. The ratio of those
weights is the specific gravity.
SImple
Bill- on Persimmon Hill
At 02:32 PM 8/20/99 EDT, you wrote: ( in part)
>----------------------------Original message----------------------------
>Hi!
>I'm a mature student (dare I say old student) half way through a two
>year Ceramic Design course at our local College here in the UK. I
>have been following the discussion of Specific Gravity and Density,
>but have a problem of my own.
> My hydrometer is scaled from 40 to 60 degrees Baume not in grams per
>millilitre or the specific gravity ratio. I would like to know what
>the relationship is between Baume and Specific Gravity.
>
>Take the Baume multiply by seventy four and divide by ten thousand
>and then add one. Forty degrees Baume comes out at 1.29 and sixty
>Baume comes out at 1.44.
>
>I could always use the hydrometer just to bring the glaze back to a
>constant gravity but I would really like to know what that gravity
>actually is in terms of Specific Gravity.
>Any help or guidance would be much appreciated
>Ivor
>(In Macclesfield, just up the road from Josiah Wedgwood's original
>pottery)
>
>
-
Bill Aycock --- Persimmon Hill
Woodville, Alabama, US 35776
(in the N.E. corner of the State)
W4BSG -- Grid EM64vr
baycock@HiWAAY.net
w4bsg@arrl.net
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