Ric Swenson on fri 18 jul 97
Dear Friends of Gerstley Borate....and non - friends of same:
(I am replying to MY OWN message... Uff da! maybe it's time to cut down
on the coffee?!)
Okay, so they (US BORAX) haven't "really" made the decision and signed a
piece of paper saying they are NOT going to mine Gerstley Borate any more.
I got the straight scoop from Dr. Jacob Mu, at the US BORAX marketing
research center in Valencia, California today.
The G. B. material is a "low grade ore" and is not consistant in quality
enough for large industrial applications.....therefore...if you don't sell
much of it....you stockpile a ten year supply and just ship to the two
suppliers in the US that still stock it. (FYI Hammill and Gillespie in NJ.
and Laguna in Cal. & elsewhere.) Use is miniscule...mostly by we (wee?
Whee? ) potters. Available will be Boron sources that are a bit more
expensive...more "refined"...but you will have to use less because it is a
higher percentage of Boric Oxide....more flux...more stable material
....fewer "secondary ingredients" (read "impuries" and "stuff".... other
than Boron.)
So, in a half hour on the phone with Dr. Mu, I learned a bit about Gerstley
Borate and Colemanite and various other Boron bearing minerals that US
BORAX supplies the world market. I tried to explain to him what CLAYART
is! God help me.
As it looks more and more like lead (and maybe Cadmium and Selenium?) in
ceramic tableware glazes and in glassware decoration will be BANNED
soon..Big manufacturers in the US...and then worldwide... will all be
looking for fluxes that work as well as lead...BUT are not such a health
hazard to makers and users. This is a good thing in my way of thinking.
(This is NOT an ad for US BOROX by the way...I have no interest in the
company ...other than the spread of real information...gleened from a
current source...of some repute. An ideal that might be worth
considering.
Dr Mu is sending me a packet of info and I will pass along a synopsis when
I have had a chance to digest it.
Hope this bit of info is helpful. I know I started reading this thread and
thought to myself...."I have not had much trouble with Gerstley Borate or
Colemanite in glazes in my nearly 30 years of "puttering about"....if
others are having troubles ...what is the deal?...what is the real story?"
Probably potters use Gerstley Borate and Colemanite in glazes because they
are the least expensive forms of boron available .... there is a history of
glaze recipes using G. B. .....will the glazes look better or worse using a
more "purified" form of Boric Oxide? Is it possible that our faithful G.
B. and Colemanite going the way of our sacred ALBANY SLIP????? ( sight
scarcastic smirk shows on authors' face...)
Get on with the potting!
In my not so humble opinion.
Ric
>----------------------------another Original
>message----------------------------
>Clayarters,
>
>I started work on a short research project regarding Gerstley Borate today.
>The first thing I learned from the US BORAX people is that they are not
>mining it any more. They figure they have a 5 to 10 year supply if G.B.
>HOWEVER...FEAR NOT....they have and will "always" have OTHER boron bearing
>stuff that will be available which will do the jobs we need/want done . (we
>shall see).
>
>We might note here that Boron and Bismuth (^$?) are starting to replace
>lead in the tableware industry ( p. 76, CERAMIC INDUSTRY, April 97
>"Solutions to lead glazes are brought to the table", by Phillip Jackson,
>PhD, Ceram Research, Stoke -on -Trent.) Worth the read.
>
>
>
>
>I will, continue to seek the Ghastley Gerstley Guru...a Dr. Wu in
>California manana por la manana.
>
>Not to worry....yet...Gerstley Borate fans.
>
> Buy "futures" in G.B. ?
>
>Happy potting.
>
>Ric
>
>
>----------------------------Original message----------------------------
>>Hi All:
>>
>>So Karl Platt's aversion to Gerstley Borate is based on probability and
>>second hand information, not practical experience and experimentation. He
>>reads posts on glaze problems and because a lot of the glazes contain
>>Gerstley Borate, that material has to be the culprit. Then, there are
>>others who write, including myself, who have used Gerstley Borate with good
>>results. It would seem that Karl is bad mouthing a material that HAS been
>>used successfully and effectively. Karl's reasons for avoiding Gerstley
>>Borate do not in any way convince me that I shouldn't use the material. As
>>Ron Roy correctly pointed out, the Neph Sy in the Berry Rust glaze could
>>very well be the offending material. People who use porcelain bodies fluxed
>>with Neph Sy have to use a newly mixed batch of clay within a couple of
>>months or the Neph Sy deflocculates the clay. So much for aging! Karl's
>>comment that anyone using GB in production is asking to go broke is a wild
>>stretch of the imagination at best.
>>
>>Sources of Calcium Borate are pretty limited. We can use GB, Colemanite (if
>>you can find it), and Calcium Borate frits. Jeff Lawrence's comment about
>>his conversation with the guy from the Ferro Corp. may very well be factual,
>>or the Ferro guy may have been embellishing the story. After all, if
>>potters use GB, they aren't going to be buying Ferro Frits. Yes, I know
>>that potters buy such a small quantity of materials in comparison with
>>industry that Ferro probably doesn't give a shit if we buy their stuff or
>>not but they still may not want to give any credence to Borax mining "by
>>products".
>>
>>For my own info, I'm going to call Indusrial Minerals on friday an see if I
>>can get their "embellishment" on the all this brew ha ha. I will also test
>>the Berry Rust glaze by using the original formula with Gerstley Borate and
>>the recalculated version with frits. I for one, would like to make some
>>first hand observations about this stuff. If you guys want me to, I'll post
>>the results to Clayart along with formulas etc. If not, I'll just go on my
>>merry way testing and trying to find out some "solid" facts. I guess it
>>seems like I'm on some kind of Crusade, but really, I'm just curious.
>>
>>Sorry about the edgy nature of this post but I've been listening to Howlin'
>>Wolf and Screamin' Jay Hawkins again. Craig Martell-Oregon
>
>Ric Swenson, Bennington College, Route 67-A, Bennington, Vermont,
>05201-6001 USA. telephone 802 442 - 5401 vox X 262 fax X 237
>direct fax line
>802 442 - 6164
>email rswenson@bennington.edu
Tom Buck on sat 19 jul 97
Ric: Like you I have a longish file on Gerstley Borate, and but for
matters beyond control, I would have written something on GB in detail. I
applaud your enterprise in telephoning a proper source. To help you along
please review the following which is assembled from bits and pieces I have
posted on Clayart over the past 15 months. Good reading.
-----
Gertsley borate: a brief portrait
US Borax has a giant deposit of Boron-containing ore in
California that it mines to process into Boron compounds (borax,
others). The potters' market is a tiny fraction of its mine output
so we get whatever comes ... US Borax sells run-of-mine ore
(Gerstley borate) as 3-inch pebble to pottery supply companies who
truck the ore themselves from the minesite. These companies,
including Hamill & Gillespie (New Jersey) and Laguna Clay
(California, etc.), pulverize/screen the ore, and bag
the powder and ship it to pottery supply companies.
The chemical makeup of the pebble undoubtedly varies from time
to time, perhaps with a swing as much as 25%. But since H&G and
Laguna do not treat the ore chemically, there is no way they can
control the boria (B2O3) content and other components. Whatever is
in the ore is what one gets.
In 1996, Laguna cited this composition (ex-US Borax):
Boric Oxide (B2O3) 28% (+/- 3%)
Sodium oxide (Na2O) 5.3%
Calcium oxide (CaO) 20.6%
Bound water ("water of crystallization") 25.0%
Moisture (average) 0.3%
Insoluble minerals (limestone, dolomite, clay, others) 18.7%
US Borax does not determine a value of importance to potters,
namely, the Loss on Ignition (LOI).
In 1992, I received this analysis from H&G and the company
has yet to supply a more current one (some data is better than
none):
B2O3 28.3%; Na2O 4.7%; SiO2 9.8%; Fe2O3 0.35%; Al2O3 1.3%;
MgO 3.5%; CaO 17.9%; K2O 0.14%; H2O (moisture) 0.52%. And the LOI
value obtained by calcining to 750 deg C was cited as 29.1%.
This analysis sums to 95.6% so one can guess that GB contains
some 4.4% of inerts (non-participants in the routine analysis
procedure). H&G said the chief components of the ore were
Colemanite (calcium borate pentahydrate) and Ulexite (a sodium /
calcium borate compound with eight moles of bound water per formula
weight).
I am using the H&G values in my glaze calc program (Insight)
and the error introduced is tolerable, since it is less than the
likely variation in the Boria content from month to month. Also, if
one puts 10% GB in a glaze mix, the difference between 25% B2O3 and
31% B2O3 becomes 2.5 vs 3.1% in the recipe, quite possibly not a
big enough swing to change the glaze's behaviour. This likely would
not be true for recipes containing in excess of 20% GB.
Gerstley borate is NOT the same as Colemanite (from a mine in
Turkey) although in most glaze mixes an equal weight of GB or
Colemanite (if available) would have much the same fluxing effects.
However, in many glaze recipes the chemical differences sometimes
do change results, especially hues, with often poor results (but
this is not vital in Raku where GB is mostly used).
An important fact: Gerstley borate (& Turkish Colemanite)
contain significant (unknown) amounts of gypsum. And it is this
mineral that earns GB its reputation for being "ghastly". Gypsum
(calcium sulfate) is a material that can cause glaze "pop-outs" if
left in the glaze mix. Fortunately, as other Clayartists have
noted, the gypsum seems more resistant to the pulverization step
than other components, and tends to remain in bigger particles.
Hence, one should always pass the GB powder through an 80/100 mesh
screen and discard the on-screen stuff. H&G says 0.3% of its GB
remains on a 70 mesh screen, and 2.5% on a 100 mesh screen. So the
extra screening step means very little GB is discarded although
most of the gypsum will stay on the 100 mesh screen.
As for the aggolmeration effect that happens in glazes with GB
in them, one can only hope for a minimum gelling if one follows a
simple procedure. Since GB is slightly soluble in water (especially
hot water), one should routinely add some Epsom salts to the water
to be used for dispersing the solids (but BEFORE adding other
solids). The presence of Mg++ ions (from magnesium sulfate)
inhibits the release of sodium ions from GB (& other ingredients)
which can gel the glaze mix. Most mixers add 1-2 teaspoons or 5-10g
of MgSO4 per kilogram of solids.
-------
And here endeth today's sermon. Good-day.
Tom Buck )
Hamilton, Ontario, Canada
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