Debby Grant on wed 16 jul 97
Many thanks to all those who answered my querry re: berry rust glaze.
I'm going to try to save the current glaze batch by adding epsom salts
as per Tom Buck's suggestion. I'm also going to mix up a new test
batch using frit # 3134 as per Craig Martell's recalculated formula. Also,
thank's to Ron Roy for comming to the defense of Gerstley Borate which
I also find to be a very useful material. I switched to it from colemanite
some 30 years ago. I suspect the real problem stems from the combination
of all 3 materials - Gerstley, NephSy and Bone Ash. I only use one
other
glaze with NephSy and Gerstley and have never had problems with it but
it does not contain Bone Ash. Incidentally, the glaze spitting onto the
kiln shelf and loss of vibrancy were far worse problems than the grit.
The grittyness or clumping could indeed be caused by the iron as Ron
suggests. I seem to remember that happening to me before in a saturated
iron glaze. Anyhow, thanks everyone. I won't be getting around to
testing for at least a month and will let you know results when I can.
Debby Grant in NH
Ron Roy on thu 17 jul 97
I am doing some work on my tenmoku glaze and thought I would mention it now
- I will fire the tests over the weekend and will be able to report results
next week.
I resieved through an 80 mesh sieve and found many black specks on the
screen which look like they may be iron - when I look at them with a
mangnifying glass they look like small round bits of iron and the fine ones
look like they may be magnetized cause they want to stay together. How they
got in the glaze is a mystery to me. Now I have to admite that glaze has
been in that bucket for well over 10 years and added to as I use it up.
Some of the original glaze is therefore still there. Anyone ever heard of
iron oxide getting together again like that?
I am also "washing" the glaze by adding water and decanting the next day.
The glaze has G200, whiting, ball clay, silica, red iron oxide (7.5%) and a
small amount of tin. It's a published glaze by the way - see "That Old
Black Magic article in CM June/July/Augest 1994 written by Tony Clennel.
>----------------------------Original message----------------------------
>Many thanks to all those who answered my querry re: berry rust glaze.
>I'm going to try to save the current glaze batch by adding epsom salts
>as per Tom Buck's suggestion. I'm also going to mix up a new test
>batch using frit # 3134 as per Craig Martell's recalculated formula. Also,
>thank's to Ron Roy for comming to the defense of Gerstley Borate which
>I also find to be a very useful material. I switched to it from colemanite
>some 30 years ago. I suspect the real problem stems from the combination
> of all 3 materials - Gerstley, NephSy and Bone Ash. I only use one
>other
>glaze with NephSy and Gerstley and have never had problems with it but
>it does not contain Bone Ash. Incidentally, the glaze spitting onto the
>kiln shelf and loss of vibrancy were far worse problems than the grit.
>The grittyness or clumping could indeed be caused by the iron as Ron
>suggests. I seem to remember that happening to me before in a saturated
>iron glaze. Anyhow, thanks everyone. I won't be getting around to
>testing for at least a month and will let you know results when I can.
>
>Debby Grant in NH
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
Studio: 416-752-7862.
Email ronroy@astral.magic.ca
Home page http://digitalfire.com/education/ronroy.htm
June Perry on fri 18 jul 97
Dear Ron:
Wonder is that's granular illmenite?? Do you think the red iron may have been
contamined with it????
Warm regards,
June
Gavin Stairs on fri 18 jul 97
At 11:19 AM 17/07/97 EDT, Ron Roy wrote:
...
>I resieved through an 80 mesh sieve and found many black specks on the
>screen which look like they may be iron - when I look at them with a
>mangnifying glass they look like small round bits of iron and the fine ones
>look like they may be magnetized cause they want to stay together. How they
>got in the glaze is a mystery to me. Now I have to admite that glaze has
>been in that bucket for well over 10 years and added to as I use it up.
>Some of the original glaze is therefore still there. Anyone ever heard of
>iron oxide getting together again like that?
Interesting. There is a form of hematite (red iron oxide) called Goethite,
if memory serves, which appears in the form of dark, almost black,
globular, "kidney" shaped clusters, with a smooth, shiny skin. It is a
semiprecious gem variety, I think. Anyway, I speculate that this forms in
stagnant pools of water rich in iron oxide. Any salt that is even slightly
soluable in water will recrystallize in this way. "Science stores", like
Edmund Scientific, are fond of selling bottles of mixed salts as "crystal
gardens". The idea is you make a supersaturated solution of the salts in
hot water, then pour them into a goldfish bowl. After a while, the salts
crystalize out, and eventually grow a cluster of largish crystals. The
same phenomenon makes geodes and hydrothermal mineralization veins of
quartz, aragonite, what have you. Of course, the "crystal gardens: grow
much faster than Ron's bucket of glaze, but... well, I'd be happy only
Goethite grew in my glaze bucket if I left it alone for... how long did you
say, Ron?
Gavin
=================================
Gavin Stairs
http://isis.physics.utoronto.ca/
Grimmer on fri 18 jul 97
Hi,
When I was in grad school, we got a batch ofIron oxide that had _loads_
of black granules in it. It seemed to get worse when it had been in a glaze for
a bit. Never did figure out why, but the next batch of the stuff was real fine
and didn't seem to give us trouble. I dunno...
steve grimmer
carterville illinois
Ron Roy wrote:
> I resieved through an 80 mesh sieve and found many black specks on the
> screen which look like they may be iron - when I look at them with a
> mangnifying glass they look like small round bits of iron and the fine ones
> look like they may be magnetized cause they want to stay together. How they
> got in the glaze is a mystery to me. Now I have to admite that glaze has
> been in that bucket for well over 10 years and added to as I use it up.
> Some of the original glaze is therefore still there. Anyone ever heard of
> iron oxide getting together again like that?
Evan Dresel on sat 19 jul 97
My guess is that the specks that look like small round bits of iron are iron
and that they got into one of your glaze materials during the grinding
process. This is only a guess, repeat only a guess but you would really
have to set up some unusual swampy, bacterially induced reducing conditions
in your bucket to form magnetite. (I do get what I believe is iron sulfide
formation in my slop bucket when it sits around and the bacteria get going.)
-- Evan in eastern Washington where it is unseasonably cool -- barely made
it into the 90s farenheit this week. I even got hit by three drops of rain
today -- a wet summer, I guess. My appologies to those of you in less
backward countries who use Celcius.
At 11:19 AM 7-17-97 EDT, Ron wrote:
>----------------------------Original message----------------------------
>I resieved through an 80 mesh sieve and found many black specks on the
>screen which look like they may be iron - when I look at them with a
>mangnifying glass they look like small round bits of iron and the fine ones
>look like they may be magnetized cause they want to stay together. How they
>got in the glaze is a mystery to me. Now I have to admite that glaze has
>been in that bucket for well over 10 years and added to as I use it up.
>Some of the original glaze is therefore still there. Anyone ever heard of
>iron oxide getting together again like that?
>
>
>Ron Roy
>Toronto, Canada
>Evenings, call 416 439 2621
>Fax, 416 438 7849
>Studio: 416-752-7862.
>Email ronroy@astral.magic.ca
>Home page http://digitalfire.com/education/ronroy.htm
>
>
Ron Roy on mon 21 jul 97
>----------------------------Original message----------------------------
>Dear Ron:
>
>Wonder is that's granular illmenite?? Do you think the red iron may have been
>contamined with it????
>
>Warm regards,
>June
Hi June - what ever it is it was not in the glaze to start with - I sieve
all glazes through 80m twice and test them before I use them.
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
Studio: 416-752-7862.
Email ronroy@astral.magic.ca
Home page http://digitalfire.com/education/people/ronroy.htm
June Perry on tue 22 jul 97
Very strange Ron. It will be interesting to hear what it is when and if the
puzzle is solved!
Maybe it's just some synergistic chemical reaction - two things combining to
make a third??????
Regards,
June
M Richens on sun 27 jul 97
In article , Ron Roy
writes
>----------------------------Original message----------------------------
>>----------------------------Original message----------------------------
>
>Hi June - what ever it is it was not in the glaze to start with - I sieve
>all glazes through 80m twice and test them before I use them.
>
>Ron Roy
Hi Ron,
I've been busy but still read the group.
Is it possible you've got a calcium carbonate build up in your slip?
When I was at a client site they had spherical dark particles in a clear
bone china glaze. Analysis showed that they were made of mostly Ca ions.
The dark colour was probably from clay contaminants as most clays and
bentonites contain some iron and lignite. (Have a look in Taylor and
Bull Chap 12.6)
Other contam might be from scoops bowls etc. If it is Iron then you can
heat the residue on a clean piece of biscuit and see if a magnet will
pick it up when it's cool.
Regards
Max
--
Max Richens max@richens.demon.co.uk +44 (0) 1925756241
Enamel Consultant - Ceramist - Analyst programmer
Software for Batch Formulation and Millroom control.
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