Susan Kosko on sun 12 may 02
i've got a generic question about calculating glaze recipes. i have a
recipe that totals 100% or 100 grams when you add up the base materials.
there are several colorants that are added and are expressed in
percentage amounts. one of the base glaze materials is barium
carbonate, for which i substitute strontium carbonate at 75% of the
amount of the barium. in order to determine the amount of colorant to
add, do i base it on the original 100% or the revised lower percentage i
get when i total the recipe using strontium?
it's a minor difference when i'm mixing a test batch, but could become
significant when mixing a full batch. i've been mixing glazes for a
number of years, but i never thought of this before - i only thought of
it because i'm testing some old copper red recipes which all contain
barium and one didn't total 100%. in the past, i've used the original
recipe to determine the amount of copper, but now i'm not sure that's
right.
thanks so much!
susan kosko
new durham, nh, usa
Ababi on sun 12 may 02
My teacher explained me once, that glazes do not have to be <100>.
There were recipes in my school that the base was 85 plus colorants and
so on.
These days when we use computers with a small click you can get the 100
= 100% yet there are some glazes that I prefer as 95 with "nice numbers
rather than 100 with 3.22 or 5.321 in it.
To your question if I understood clearly.
I add here a recipe, to help the explanation from Penland school:
.WOO YELLOW 1
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Cone 6 1201 deg.C. -
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
FELDSPAR SODA F7/SE 36.00
Barium Carbonate 20.00
Dolomite 13.00
EPK Kaolin 8.00
SILICA 8.00
ULTROX 15.00
Red Iron Oxide 3.00
==========================
You need 0.75 of the barium
So here:
.WOO YELLOW 2
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Cone 6 1201 deg.C. -
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
FELDSPAR SODA F7/SE 36.00
STRONTIUM CARBONATE 15.00
Dolomite 13.00
EPK Kaolin 8.00
SILICA 8.00
ULTROX 15.00
Red Iron Oxide 3.00
Much better than the next way:
.WOO YELLOW 2
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Cone 6 1201 deg.C. -
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
FELDSPAR SODA F7/SE 37.89
STRONTIUM CARBONATE 15.78
Dolomite 13.68
EPK Kaolin 8.42
SILICA 8.42
ULTROX 15.78
Red Iron Oxide 3.16
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
About copper red you must find out if the strontium work the way the
barium does. It does work like barium with turquoise, copper too, but
copper red is beyond my knowledge
Was it the right answer?
Ababi Sharon
Kibbutz Shoval- Israel
Glaze addict
ababisha@shoval.org.il
http://members4.clubphoto.com/ababi306910/
http://www.milkywayceramics.com/cgallery/asharon.htm
---------- Original Message ----------
> i've got a generic question about calculating glaze recipes. i have
a
>recipe that totals 100% or 100 grams when you add up the base materials.
> there are several colorants that are added and are expressed in
>percentage amounts. one of the base glaze materials is barium
>carbonate, for which i substitute strontium carbonate at 75% of the
>amount of the barium. in order to determine the amount of colorant to
>add, do i base it on the original 100% or the revised lower percentage i
>get when i total the recipe using strontium?
>it's a minor difference when i'm mixing a test batch, but could become
>significant when mixing a full batch. i've been mixing glazes for a
>number of years, but i never thought of this before - i only thought of
>it because i'm testing some old copper red recipes which all contain
>barium and one didn't total 100%. in the past, i've used the original
>recipe to determine the amount of copper, but now i'm not sure that's
>right.
>thanks so much!
>susan kosko
>new durham, nh, usa
>________________________________________________________________________
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>melpots@pclink.com.
Tom Buck on mon 13 may 02
Susan:
When a glaze is prepared from a batch recipe, the actual amounts
weighed out do not tell you what is left on the pot after it is fired to
maturity. For that info you have to switch to moles.
say you have 20 grams of Barium Carbonate in the recipe. When
fired this results in 0.10 mol of BaO in the pot's glaze.
you sub 15 grams of Strontium Carbonate for the BaCO3. When fired
the 15 grams yields 0.10 mol of SrO on the pot's glaze.
as you can see you get exactly the same result in "Molar" terms
with the different amounts of BaCO3 and SrCO3
Conclusion: when you sub SrCO3 for BaCO3, all the rest of the
batch recipe including percent weight additions of colourants remain
unchanged. Even tho' the batch recipe base now adds to less than 100.
The original recipe was designed to use BaCO3; hence, the weight
percent values were proportioned to add to 100 + colourants.
Now, if you want to redesign the recipe to use SrCO3, so that the
base recipe adds to 100, you must adjust the values of all ingredients to
accomodate the lower molecular weight of SrCO3. I do this automatically
via computer.
later. Peace. Tom B.
Tom Buck ) -- primary address.
"alias" or secondary address.
tel: 905-389-2339 (westend Lake Ontario, province of Ontario, Canada).
mailing address: 373 East 43rd Street, Hamilton ON L8T 3E1 Canada
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