Lesley Alexander on fri 4 sep 98
Why strontium carbonate 75% as a sub for barium 100%? I've tried
glaze tests 100% for 100% and can't see any difference. According to
"Insight" software, strontium has an atomic weight of 147.58 while barium
has 197.4, in case that's relevant. Anyone with experience or theory about this?
Tom Buck on sat 5 sep 98
Lesley A:
Lots of data on this in the Clayart Archives which is worth
looking at.
Both Strontium and Barium are listed in the Periodic Table of the
Elements, Group IIA metals (Alkaline Earths). Strontium is Element 38 (ie,
its Atomic No. is 38 which means it has 38 protons in its nucleus). Barium
is Element 56 (AN 56). In network polymers like glass, Barium atoms
display a bigger influence on their surroundings than do Strontium atoms.
Yet, both these elements, when combined with Oxygen in glass, behave in
similar ways. The main difference is the degree that each atomic species
affects the alumino-silicate structure of glass. In gross terms, Barium
Oxide is used by potters for Matt Glazes and for the colours it produces
from Copper Oxide and other colourant oxides. Strontium Oxide does this
also but the mattness and colour responses are different, some say
subdued. Like always, though, Beauty is in the eyes of the beholder.
The common compound available to potters is the carbonate, either
BaCO3 or SrCO3. The Barium form is quite poisonous and must be handled
with great care; and in some glazes the Barium, if used on foodpots, may
prove dangerous to the pot users. Which is why the more expensive SrCO3 is
now replacing it since SrCO3 is tolerated by the human body in much the
same fashion as Calcium Carbonate (Calcium atoms are needed to keep our
bones healthy).
The basic mass unit of chemical compounds is the molecule, and one
molecule of SrCO3 weighs 147.63 in atomic mass units; one molecule of
BaCO3 in the same units is 197.35 which means 1 molecule of SrCO3 will
replace 1.34 molecules of BaCO3 in the glaze structure, or rephrasing it,
75 grams of SrCO3 is equivalent to 100 grams of BaCO3.
Sure, you can use more SrCO3 in the recipe, say the same number
used for BaCO3, but it aint the same recipe anymore. Which in many cases
really won't matter since the Barium Matts generally exhibit varying
results on different claybodies. But there are potters who love their
Barium Matts and will defend them to the death.
Bye for now.
Tom Buck ) tel: 905-389-2339
& snailmail: 373 East 43rd St. Hamilton ON L8T 3E1 Canada
(westend Lake Ontario, province of Ontario, Canada).
On Fri, 4 Sep 1998, Lesley Alexander wrote:
> ----------------------------Original message----------------------------
> Why strontium carbonate 75% as a sub for barium 100%? I've tried
> glaze tests 100% for 100% and can't see any difference. According to
> "Insight" software, strontium has an atomic weight of 147.58 while barium
> has 197.4, in case that's relevant. Anyone with experience or theory about thi
>
Bill Aycock on sat 5 sep 98
Lesley- the answer is contained i your posting- if you will divide the
atomic weight of the Sr (147.58) by the atomic wt of the Ba (197.4) you
will get pretty close to 75%. (actually, you should use the formula weights
of the oxides, but this is close)
The answer is that you want to match the relative number of molecules, and
not the weight. To do this, more weight of the heavier molecules gives the
same number of molecules a less weight of the lighter.
As an important quibble, many of us speak of "Barium" and "Strontium", when
what we are really dealling with is the oxides ( or Carbonates) of the
elements. We dont say "Hydrogen" when we mean "water", or "Silicon" when
we mean "Silica", do we?
Bill- quibbling down the court, on Persimmon Hill
At 08:47 AM 9/4/98 EDT, you wrote:
>----------------------------Original message----------------------------
> Why strontium carbonate 75% as a sub for barium 100%? I've tried
>glaze tests 100% for 100% and can't see any difference. According to
>"Insight" software, strontium has an atomic weight of 147.58 while barium
>has 197.4, in case that's relevant. Anyone with experience or theory about
this?
>
>
Bill Aycock --- Persimmon Hill
Woodville, Alabama, US 35776
(in the N.E. corner of the State)
W4BSG -- Grid EM64vr
baycock@HiWAAY.net
Mason Batchelder on fri 2 apr 99
I am noticing the extensive use of Strontium being used now and want to ask
this question.When I took Pete Pinnell's class at ARROWMONT he mentioned that
where you get your Strontium from was important and he had a specific place
he felt had a much better grade.Has that situation changed and since my
glaze notes/books were lifted I do not know what the place he mentioned was
nor if it is still doing business.I also lost my notes on a great tile press
he made and gave us plans for....anyone have that?
MARGARET IN Lexington,S.C.,USA(100 miles south of NCECA 2001 site).
M.S. Flood on tue 6 apr 99
At our studio we use the Pinnell strontium glazes, and we have found that the
granular strontium works much better than the powdered form. Up until now,
Minnesota Clay Co. was the source we used, and they always sent granular. I jus
ordered some, however, and they sent five one pound packages, some of which were
in older looking wrappings. When we were dumping these into our leftover granula
strontium (that had also been purchased from Minnesota Clay) we found that two o
the packages were powdered, not granular. This contaminated our entire supply.
I am in the proces of contacting Minesota Clay about this to see about some
replacement strontium, since they sent two different kinds. I have never had
this problem with strontium from them before, and assume they had some older
stock they mixed in with the newer stock. Usually, five pounds of strontium fro
them comes in one container, not five separate bags. Hopefully, we can work thi
out.
Before you purchase strontium, I'd ask your supplier what form of strontium they
will be shipping. Good luck.
Bridget McDermott Flood
fireworks studio
St. Louis, MO
Mason Batchelder wrote:
> ----------------------------Original message----------------------------
> I am noticing the extensive use of Strontium being used now and want to ask
> this question.When I took Pete Pinnell's class at ARROWMONT he mentioned that
> where you get your Strontium from was important and he had a specific place
> he felt had a much better grade.Has that situation changed and since my
> glaze notes/books were lifted I do not know what the place he mentioned was
> nor if it is still doing business.I also lost my notes on a great tile press
> he made and gave us plans for....anyone have that?
> MARGARET IN Lexington,S.C.,USA(100 miles south of NCECA 2001 site).
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