Craig Martell on wed 21 feb 07
Hi:
If I'm reading some posts correctly it's been said that you can mix a glaze
by volume or weight and come up with the same glaze as long as everything
adds up to 100%. Is that right? Did I read this stuff correctly?
So if I have a very simple glaze, for example and simplicity, 50% g-200
spar and 50% epk kaolin, I will have exactly the same glaze if I weigh out
50 grams of spar and 50 grams of epk or if I use 1 cup or spar and 1 cup of
epk. Well, it doesn't pan out at all. I measured out equal amounts of each
and weighed both. It was about 3/4 cup of g-200 and epk, the weight was
not even close. g-200 is 207.2 grams and epk is 134.5.
regards, Craig Martell Hopewell, Oregon
Craig Clark on wed 21 feb 07
Thank you for the observation Craig. I was gonna git around to
pointing out what you have mentioned but find myself piling on instead.
If there is a notion that one can make a one to one type of volumetric
to weight comparison it is indeed patently wrong. The only way that this
would work is if there were a similar density to the materials being
compared. I don't know who started this type of argument but I suggest
that they check their math before posting such wrong headed information.
I am fully aware that there are great many folks who do indeed make
glazes based upon volume. I happen to be one when it comes to some of my
Raku glazes. This does not mean that the aforementioned comparisons are
even remotely valid. Weight is weight. Volume is volume. They are
different means of measurement. Results can be radically different when
one attempts to translate volumetric based measurement of the components
of a glaze to a similar type of percentages based on weight.
Craig Dunn Clark
619 East 11 1/2 St
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
Craig Martell wrote:
> Hi:
>
> If I'm reading some posts correctly it's been said that you can mix a
> glaze
> by volume or weight and come up with the same glaze as long as everything
> adds up to 100%. Is that right? Did I read this stuff correctly?
>
> So if I have a very simple glaze, for example and simplicity, 50% g-200
> spar and 50% epk kaolin, I will have exactly the same glaze if I weigh
> out
> 50 grams of spar and 50 grams of epk or if I use 1 cup or spar and 1
> cup of
> epk. Well, it doesn't pan out at all. I measured out equal amounts of
> each
> and weighed both. It was about 3/4 cup of g-200 and epk, the weight was
> not even close. g-200 is 207.2 grams and epk is 134.5.
>
> regards, Craig Martell Hopewell, Oregon
>
> ______________________________________________________________________________
>
> Send postings to clayart@lsv.ceramics.org
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>
Kathy McDonald on wed 21 feb 07
Craig..
I don't believe this to be true.
I know that a cup of Cornwall stone does not weigh
the same as a cup of gerstley borate,
.............and that when you get a 100 g bag of Cerdec
orange stain and
100 g of Mason royal blue they are different by volume.
I don't know all the physics and molecular theory behind
this but many others on the list do.
I wish it were that simple.
Kathy
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG]On Behalf Of
Craig Martell
Sent: Wednesday, February 21, 2007 12:50 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: mixing glazes-volume/weight
Hi:
If I'm reading some posts correctly it's been said that you
can mix a glaze
by volume or weight and come up with the same glaze as long
as everything
adds up to 100%. Is that right? Did I read this stuff
correctly?
So if I have a very simple glaze, for example and
simplicity, 50% g-200
spar and 50% epk kaolin, I will have exactly the same glaze
if I weigh out
50 grams of spar and 50 grams of epk or if I use 1 cup or
spar and 1 cup of
epk. Well, it doesn't pan out at all. I measured out equal
amounts of each
and weighed both. It was about 3/4 cup of g-200 and epk,
the weight was
not even close. g-200 is 207.2 grams and epk is 134.5.
regards, Craig Martell Hopewell, Oregon
____________________________________________________________
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melpots@pclink.com.
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Ivor and Olive Lewis on thu 22 feb 07
Dear Craig Martell=20
I think I said that with percentages you could select any weighing units =
system you pleased to use. But if you insisted on measuring by volume =
you have to take Density into account.
Take a bushel of Kaolin, three pecks of Custer spar a fluid ounce of =
Cobalt oxide......
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Snail Scott on thu 22 feb 07
At 10:50 AM 2/21/2007 -0800, you wrote:
>
>If I'm reading some posts correctly it's been said that you can mix a glaze
>by volume or weight and come up with the same glaze as long as everything
>adds up to 100%. Is that right? Did I read this stuff correctly?
I think what was meant is that a percentage
is always a percentage, and it doesn't
matter if the weight unit used is pounds,
grams, troy ounces, cans of peas or
whatever, or if the volume unit used is
cups, teaspoons, coffee cans, or buckets.
You just need to know whether the recipe
was written for weight or volume. The
vast majority of recipes are weight-based,
so unless otherwise specified, assume that
weight is the intended measurement system.
To convert between systems, each ingredient
quantity needs to be modified to compensate
for its weight. No single formula will
convert a weight percentage recipe to a
volumetric one; the ratio of weight to
volume must be known for each material.
This can be done mathematically, or by
experiment.
A recipe composed for volumetric measure
will likewise require an item-by-item
conversion to measure it by weight.
Some people like one system or the other,
but they tend to stick to one or the other,
doing all their glaze development by a
single system, not by conversion.
I find it tough to measure accurately
when doing small test batches by volume.
It would work better for large batches, but
I seldom use very large glaze quantities.
Volume is a great for clay mixing, though,
since quantities tend to be larger, and
precise measurement is less critical.
-Snail
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