Paul Lewing on tue 30 jan 01
Llewellyn Kouba wrote:
> I am mixing some test glazes and have a formula that calls for 1,720 grams
> of Colemanite. Is there a substitution or frit that I should try as a
> replacement here?
Sure is! You must have an old recipe there. I remember when colemanite
became unavailable, and there was a new material on the market that we
just substituted straight across, with no noticable change in the fired
glazes. The new stuff was called gerstley borate!
But colemanite is supposedly calcium borate, a much simpler material
than GB, and that's pretty much what Cadycal is, as well.
(I know strontium is a sub for barium at 10% less)
Actually, the substitution is, you use 70% as much strontium carbonate
as barium carbonate.
Paul Lewing, Seattle
Craig Martell on tue 30 jan 01
Llewellyn wanted to know if:
>I am mixing some test glazes and have a formula that calls for 1,720 grams
>of Colemanite. Is there a substitution or frit that I should try as a
>replacement here? (I know strontium is a sub for barium at 10% less)
Cadycal 100 is a calcium borate material that is almost a dead ringer for
Colemanite. From the data I have and the fusions I've done, it's a direct
sub or very close. As far as I've seen, there isn't a frit anywhere that's
as close as Cadycal.
regards, Craig Martell in Oregon USA, 45th parallel
Llewellyn Kouba on tue 30 jan 01
Readers,
I am mixing some test glazes and have a formula that calls for 1,720 grams
of Colemanite. Is there a substitution or frit that I should try as a
replacement here? (I know strontium is a sub for barium at 10% less)
Llewellyn Kouba
Randall Moody on tue 30 jan 01
It is my understanding that Gerstley Borate was the substitution for
Colemanite. Now with GB gone or going the jury is still out on what is the
best sub for it. The studio where I work uses Murray's Borate from Kickwheel
Pottery supply in Atlanta. There seems to be a problem with it settling too
quickly so we put in a certain amount of bentonite to compensate. I think
that it is ~8% of the amount of Murray's Borate called for in the recipe.
--Randall--
>
> I am mixing some test glazes and have a formula that calls for 1,720 grams
> of Colemanite. Is there a substitution or frit that I should try as a
> replacement here? (I know strontium is a sub for barium at 10% less)
Lili Krakowski on wed 31 jan 01
On Tue, 30 Jan 2001, Llewellyn Kouba wrote:
> Readers,
>
> I am mixing some test glazes and have a formula that calls for 1,720 grams
> of Colemanite. Is there a substitution or frit that I should try as a
> replacement here? (I know strontium is a sub for barium at 10% less)
>
> Llewellyn Kouba
>
Oy! Ok. Colemanite was a naturally found calcium borate. I beleive it
used to be mined in several places in the world. They stopped mining it
in the US, so there was a lot of crying, cursing, swearing--this
all happened some 40 years ago (just about) and we all used Gerstley
Borate. Recently GB went off the market and so on.
BUT there are numbers of calcium borate frits on the market. The
suppliers are now introducing NEW frits that are supposed to replace GB
more closely than what is already on the market. Nevertheless I have
found Frit 3124 a very good 1 on 1 replacement. And I have for many
years replaced all colemanite/gb in new glazes (i.e. glazes I read about
and want to try) with 3124 , as well as substituting 3124 for c/gb in old
glazes I have long used.
So give that a whirl. (WEAR YOUR MASK!)
Just remember this : C/GB essentially are 1 part calcium to 1.5 part
boron. As there are lots of sources of calcium, but only frits now
supply boron in a non-water-soluble form. Find a frit that supplies your
BORON need first. Adjust the calcium with other ingredients, my favorite
being Wollastonite (whiting shrinks too much) As both c and gb varied from
batch to batch you will do ok, frits being quite consistent.
good luck, be of good courage
> ______________________________________________________________________________
> 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.
>
Lili Krakowski
| |
|
