Eddie Krieger on sun 31 mar 02
I just tried to use some Strontium CO3 in a new glaze formula and was
surprised and dismayed at the particle size.
Am I supposed to grind this stuff in a mortar before I use it? When I tried
to strain or sift this stuff through a 60 mesh screen all the strontium was
left in the strainer.
What's the answer? And, another question: I think this is a substitute for
Barium CO3 but isn't the ratio by weight 25% less Strontium to Barium. Read
this somewhere but can't remember where.
Thanks
Eddie Krieger
Dry Creek Pottery
Abilene, TX
Tom Buck on sun 31 mar 02
Eddie K
if you are using say 20%w of SrCO3 in a glaze, then yes you will
have to hand-grind it or ballmill the glaze so it will pass through 60
mesh (80 m is better). and 100 weight units of Barium Carbonate is
equivalent to 75 weight units of Strontium Carbonate:
Ba has an atomic weight of 137.3; Sr = 87.6; C=12; O=16 and so the
Molecular Wt of BaCO3 = 137.3+12+3x16= 197.3
" " " SrCO3 = 87.6+60 = 147.6
and 1 mole of each replaces 1 mole of the other, hence, in weight units:
100 (BaCO3) / 197.3 x 147.6 = 74.81 (SrCO3), or 100 (SrCO3) / 147.6 x
197.3 = 133.7 (BaCO3).
good tests Peace. Tom B.
Tom Buck ) tel: 905-389-2339
(westend Lake Ontario, province of Ontario, Canada).
mailing address: 373 East 43rd Street,
Hamilton ON L8T 3E1 Canada
Tom Buck on mon 1 apr 02
On Mon, 1 Apr 2002, Jim V Brooks wrote:
> Mr. Buck.........I dont understand.!!!!. What does the amount (percentage)
> of Strontium in glaze have to do with getting it thru a sieve? I use 20%
> or more sometimes and i never have to hand grind it. Call your supplier..
> and tell him your returning this to him..!!! You need a smaller grind to
> begin with....say a 200 mesh...or 300 mesh. The size of the particle is what
> determines if it will go thru your 60 mesh or 80 mesh sieve... Jim in
> Dallas....
-----------------------
Jim Brooks:
You ask about the behaviour of Strontium Carbonate of large
particle size. If you used small amounts of SrCO3 in a glaze, even though
the particle sizes were large (relatively), you'd stand a chance that the
SrO formed in due course (at close to Cone 10) would be able to disperse
throughout the liquidus (molten glass), and particpate in the fluxing of
the glaze being formed. Whereas that would be difficult with SrCO3
constituting a substantial (say more than 20 mol%) amount of the flux
oxides because the SrCO3 "clumps" would be less active/mobile, and so SrO
may not be formed to diffuse throughout the liquidus. The unreacted
SrCO3 would lead to unwanted glaze imperfections.
there was a discussion on SrCO3 about a year ago (or earlier)
wherein it was claimed that different grades of the Strontium Carbonate
were being offered for sale by suppliers in different parts of North
America. and some potters reported poor results when using the "SrCO3"
they bought.
The original post asked two questions: 1) how difficult is it to
grind SrCO3? and 2) what is the relationship between Barium Carbonate and
Strontium Carbonate?
If you were supplied with crude Strontium mineral, likely it would
be celestite, SrSO4 (the sulfate) and the mineral would be amenable to
mortar and pestle grinding (it's Mohr hardnes rating is 3 - 3.5, ie, low),
and this would be needed to get the mineral through a 60 mesh screen.
as for the converting factor: 100 BaCO3 = 75 SrCO3 and I gave the
maths to verify that. If mineral celestite were substituted by your
supplier, then it would be a toss-up, I'd use the same amount of SrSO4 as
the BaCO3 in the recipe.
til later. Peace. Tom B.
Tom Buck ) tel:
905-389-2339 (westend Lake Ontario, province of Ontario, Canada).
mailing address: 373 East 43rd Street,
Hamilton ON L8T 3E1 Canada
Jim V Brooks on mon 1 apr 02
Mr. Buck.........I dont understand.!!!!. What does the amount (percentage)
of Strontium in glaze have to do with getting it thru a sieve? I use 20%
or more sometimes and i never have to hand grind it. Call your supplier..
and tell him your returning this to him..!!! You need a smaller grind to
begin with....say a 200 mesh...or 300 mesh. The size of the particle is what
determines if it will go thru your 60 mesh or 80 mesh sieve... Jim in
Dallas....
Pete Pinnell on mon 1 apr 02
If I were you, I would return that stuff to the supplier. There are many
different grades of strontium carbonate available to them, and your
supplier is stocking some rather poor stuff. A good, ceramic grade
strontium carbonate should be a bright, fine, white powder that looks
like a good grade of whiting and passes easily through a 60 mesh screen.
If it doesn't, send it back.
Since I often use strontium carbonate in glaze formulas, I get many
inquiries from potters when their glazes don't work. Inevitably, the
problem turns out to be a coarse or impure grade of strontium. Just out
of curiosity's sake, I have tried ball milling some of the coarse, tan
colored strontium that is sold, and it still didn't work- which leads me
to believe there must be other impurities involved.
Besides the difficulty in getting the stuff through a screen, there are
a couple of other glaze flaws that seem to stem from this stuff,
including pinholing, and excessive running. For instance, my Weathered
Bronze glaze should not run at cone 9 reduction, and should not develop
pinholes on a clean clay body, two problems I often see when others use
it.
Sometimes I feel like that announcer at Woodstock: "Hey people, there's
some bad strontium out there!" (Am I showing my age with this arcane
reference?)
Pete Pinnell
> I just tried to use some Strontium CO3 in a new glaze formula and was
> surprised and dismayed at the particle size.
>
> Am I supposed to grind this stuff in a mortar before I use it? When I tried
> to strain or sift this stuff through a 60 mesh screen all the strontium was
> left in the strainer.
>
> Thanks
>
> Eddie Krieger
> Dry Creek Pottery
> Abilene, TX
>
Ruth Ballou on mon 1 apr 02
You're right, Jim. There are two different grades of Strontium Carbonate
out there. One is granular, the other is a powder. Not sure of the mesh
size, but there's no problem getting it through a 60 mesh screen......
Ruth Ballou
Silver Spring,MD
Where I'm waiting for the cherry blossoms in the neighborhood to bloom.
Tried to see the ones in DC one year and only got close enough to see a
pink haze in the distance.
> Mr. Buck.........I dont understand.!!!!. What does the amount (percentage)
>of Strontium in glaze have to do with getting it thru a sieve? I use 20%
>or more sometimes and i never have to hand grind it. Call your supplier..
>and tell him your returning this to him..!!! You need a smaller grind to
>begin with....say a 200 mesh...or 300 mesh. The size of the particle is what
>determines if it will go thru your 60 mesh or 80 mesh sieve... Jim in
>Dallas....
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
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>
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>melpots@pclink.com.
Wanda Holmes on mon 1 apr 02
Pete, I got the Woodstock reference, Power to the people, Man! wanda
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG]On
Behalf Of Pete Pinnell
Sent: Monday, April 01, 2002 8:58 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: strontium carbonate question
If I were you, I would return that stuff to the supplier. There are many
different grades of strontium carbonate available to them, and your
supplier is stocking some rather poor stuff. A good, ceramic grade
strontium carbonate should be a bright, fine, white powder that looks
like a good grade of whiting and passes easily through a 60 mesh screen.
If it doesn't, send it back.
Since I often use strontium carbonate in glaze formulas, I get many
inquiries from potters when their glazes don't work. Inevitably, the
problem turns out to be a coarse or impure grade of strontium. Just out
of curiosity's sake, I have tried ball milling some of the coarse, tan
colored strontium that is sold, and it still didn't work- which leads me
to believe there must be other impurities involved.
Besides the difficulty in getting the stuff through a screen, there are
a couple of other glaze flaws that seem to stem from this stuff,
including pinholing, and excessive running. For instance, my Weathered
Bronze glaze should not run at cone 9 reduction, and should not develop
pinholes on a clean clay body, two problems I often see when others use
it.
Sometimes I feel like that announcer at Woodstock: "Hey people, there's
some bad strontium out there!" (Am I showing my age with this arcane
reference?)
Pete Pinnell
> I just tried to use some Strontium CO3 in a new glaze formula and was
> surprised and dismayed at the particle size.
>
> Am I supposed to grind this stuff in a mortar before I use it? When I
tried
> to strain or sift this stuff through a 60 mesh screen all the strontium
was
> left in the strainer.
>
> Thanks
>
> Eddie Krieger
> Dry Creek Pottery
> Abilene, TX
>
____________________________________________________________________________
__
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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