Fred Parker on wed 21 feb 07
To anyone who read (and believed) my posting below re interchangeability
of units when mixing glazes...
Kate:
Many Clayarters have responded with a correction to the notion that
unit=unit no matter what they might be. I was very wrong. They are very
right. Volumetric units are not interchangeable. A cup of lead is not
the same "amount" as a cup of feathers. Nor is a glass of air the
same "amount" or weight as a glass of a good, single-malt Scotch whiskey.
The only way "unit=unit" works is in measuring weights. A gram is a
gram. A pound is a pound. An ounce is an ounce. A pound of lead weighs
the same (is the same "amount") as a pound of feathers.
What was I thinking?...
SO. You can mix in grams, pounds, ounces, kilograms, tons, but you should
NOT (without tediously derived conversion factors) mix in cups,
wheelbarrows, rail cars or handsful.
And Kate, I'll repeat what Lili already said, "Wear a mask!" It should be
a P-100 rated respirator (costs around thirty bucks) -- not one of those
paper masks with a rubber band. They do NOT work for what you are doing.
Sorry for the lapse..
Fred Parker
On Tue, 20 Feb 2007 21:33:04 -0500, Fred Parker
wrote:
>Hi Kate:
>
>I started mixing glazes about a year ago, and have learned a ton since
>then! I hope some of this will be useful to you:
>
>Percentages in a formula translate to grams, cups, gallons, pounds, or
>whatever unit you want to use PROVIDED you mix 100 of those units in a
>batch. Hence, for a 100 gram batch of the glaze you cited you would mix
>25 grams of rutile, 50 grams of feldspar and 25 grams of gerstley borate.
>For a 200 gram batch, mix two times these amounts.
>
>Note that most recipes will give the ingredients of the base glaze, then
>they will indicate ADDITIONS of colorants. In your glaze, for a blue, it
>might say, "add: 2% cobalt carbonate" for example. This 2% is 2% of the
>base glaze batch. Again, if your batch is 100 grams, then you would add 2
>grams of cobalt carbonate for a total batch weight of 102 grams. If your
>batch size were 200 grams, you would add 2% of 200 grams, or 4 grams for a
>total batch weight of 204 grams.
>
>COnverting to other units is no more than simply using other units. If
>you wanted a 204 pound quantity of the glaze, you would mix 200 POUNDS
>(not grams) of teh base glaze, then add 2% of that weight (4 POUNDS) of
>cobalt carbonate for a total of 204 POUNDS. Ditto cups, handfuls or
>wheelbarrows. Just use the same unit for ALL the ingredients AND make
>sure each cup, handful, wheelbarrow etc. contains the same amount.
>
>Feel free to write off list if I can answer any questions you might have.
>
>Regards,
>
>Fred Parker
>
>On Mon, 19 Feb 2007 22:04:42 -0500, Kate Mckinley
>wrote:
>
>>Hi there,
>>I am in the process of trying to make my own glazes. I want to make sure
>I
>>have this right. If a recipe calls for chemicals, for instance:
>>
>>Rutile 25%
>>Feldspar 50%
>>Gertsley Borate 25%
>>
>>Do these percentages refer to grams? and also if I want to double or
>>triple the recipe, do I just times by that number? Any help is
>>appreciated. Is there anyway to convert these percentages to measurments
>>like 1/2 cups, cups, etc?
>>Thanks all help is appreciated.
>>Kate
>>
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>
>__________________________________________________________________________
____
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
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