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Basic Internet Glaze Course

By Lili Krakowski

 

To get the formula,  we divide each material by its molecular weight,
which we find listed in glaze books.
 
Whiting (calcium carbonate)  has a molecular weight of 100.
 
Dividing our 32 gms of whiting by molecular weight of 100 we get .3200.
 
We divide the zinc we have-12 gms-by 81 and get  .1481.
 
And we skip to the flint ( you will see why)  and divide 17 by 60 =.2833.
 
Now we get to a bit more complicated stuff.  The dolomite and the clay.
Both have two components, two materials.
 
Dolomite has 1 calcium and 1 magnesium.  And dividing the 15 gms in our
recipe, we get .0815 of EACH.
 
With clay we get 24 divided by 258.  Or  .0930.  But wait a minute.  Here we
have two parts of silica for one of alumina.  So we multiply the .0930 by
two, and get .1860
 
To finish our formula properly we add up all the fluxes and write them down
in a column, all the stickers in their column, and the glass-formers in the
third column.
 
Because we have more than one source of a specific ingredient-in this case
calcium-- we put down what each material contributes, and add that up for
the total we will be getting of that ingredient.
 
CaO  .3200 + .0815 = .4015
MgO                           .0815
ZnO                           .1481
 
Al2O3                         .0930
 
SiO2  .2833 + .1860 =  .4693
 
To tidy this up, we reduce it to unity.  To see to it that the
flux/melter/RO column adds up to 1, and the other columns are adjusted
accordingly.  We add up the RO column for a total of .6311, and then divide
every ingredient in the whole formula by that number.
 
 
Result:
 
CaO  .6362
MgO .1291
ZnO  .2347
 
Al2O3   .1475
 
SiO2      .7436
 
At this point you are all upset and in a small panic.
 
But look.  If you need 24 ounces of chocolate chips, and you can get the
chips only in  7 oz packets, what do you do?  You divide your NEED (24 oz)
by your supply (7 oz packets)   and  learn you will need 3.428 packets.
 
Your cookie recipe includes flour, sugar, butter, eggs, milk.  So when you
get to the fat/protein/carbohydrate part you actually follow the same
procedure as above.
 

 

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Originally written for Clay Art Listserv and reprinted here by kind permission of Lili Krakowski.