Lili Krakowski on thu 14 sep 06
Cliff: You are on the right track. You are calculating your glazes and
figuring out what actually is in them. Not essential as good glazes were
made for centuries before Hermann Seger came along, but today calculating is
a welcome "shortcut" to knowledge about glaze stability. (And, Roy, still
got my slide-rule in the studio...)
The weather is dreadful, AND the chiropractor warned me to give my shoulders
a rest for a few days, so I recalculated Cliff's glaze.
I cannot get Gerstley Borate, many others can't either, and I hated the
stuff when it was around. Here I used frits.
Frit 3195 21.8
Frit 31.85 23.9
Dolomite 12.7
Kaolin 12.9
Whiting 12.6
Flint l6.1
The formula looks like this:
Na2O .141
K2O .002
MgO .184
CaO .673
Al2O3 .201
B2O3 .559
SiO2 2.024
And the COE is 68.06. Both the alumina and silica are within the "limits"
as is the COE. There is a little bit more soda, and a little less boron. I
doubt that will matter.
I think, Cliff, you might want to read ABOUT the materials in as many books
as you can find. Interloan at your Public Library will get you lots of
good books. Many materials are listed as fluxes, for instance, but that does
not mean they necessarily act the same way, esp. with finishes (shiny,
satiny) and with color. I might add I was astonished a few days ago that
a fellow ClayArter was not familiar with the Internet used book sellers:
Biblio, Abebooks, Alibris, AddAll..and there may be more. But these sellers
keep me from illiteracy....
Back to clay. This AM I read this recipe on ClayArt:
>> Neph Sy 120
>> Lithium Carbonate 65
>> Whiting 15
>> Barium Carb 115
>> Ball clay 15
>> Flint 155
>> Frit 3124 50
>> Chrome OX 2.5
whose formula turns out to be:
LiO2 .409
Na2O .113
K2O .029
CaO .174
BaO .273
Al2O3 .152
B2O3 .046
SiO2 1.925
With a COE 78.99
The alumina and silica are below the limits. I would think this an
unstable glaze. Then it contains BARIUM, which, thank goodness, the clay
community now agrees is a no-no. Then there is lithium--12.5% of , which is
high. And then there is, the chromium.
Last week we had another go-around on lithium. Edouard Bastarache told us
none of the professional literature mentions any case of someone being
poisoned by accidental ingestion of lithium. I do not doubt this, at all.
But I do not know whether a regular MD or Emergency Room, getting in a
bi-polar patient on lithium meds, and with overdose symptoms would realize
this was not a suicide attempt, nor badly adjusted meds, but getting lithium
into the system from lithium dust in the studio. And even if they did
realize it, would they necessarily report it to "the professional
literature."
And then the chromium--about which Monona Rossol has a bit to say in the
May/June/06 CLAY TIMES .
What concerns me so very much is glaze recipes like the above being "out
there". An occupational therapist, a school teacher, just a plain "newbie"
can get lithium, barium, chrome without any warning label on the bags. Oh
sure, you are supposed to get MSDS sheets with the materials--but one does
not when buying in very small quantities. And even in a school or similar
where materials are bought in 50 lbs sacks, MSD sheets supplied, does
everyone read them? Does everyone who handles the materials have a properly
fitted mask? Shower and shampoo and put on fresh clothes when the weighing
out and mixing has been done? I will not go on, you get the picture.
Some years ago Monona Rossol published in her CT column the findings of one
Lynn Barth who went to a great deal of trouble to make up a list of Safer
Glaze Ingredients and Safer Colorants and Opacifiers.
Bone Ash
Dolomite
Kaolin and Other Clays
Magnesium Carbonate
Nepheline Syenite
Potassium and Sodium Feldspars
Whiting
Wollastonite
Copper Oxides
Iron Oxides and Ilmenite
Tin Oxide
Titanium Oxide and Rutile
Zinc Oxide
Zirconium Silicate
Monona cautions that mined substances often are contaminated with other
materials and the material data sheet should be read.
Concern IS out there. I cannot imagine that "we" cannot think up a way to
protect newbies, who do not "question" recipes,
who think any nice white powder is like flour or sugar; school teachers
and therapists who just are not sufficiently informed;
janitors who sweep and mop up spills and wipe counters without masks and
other precautions because no one told them...
Could we not think of some way? We live by our ideas...let's think
something up.
Lili Krakowski
Be of good courage
Nancy Braches on fri 15 sep 06
Lili
Thank you for the post. Yep I am a newbie to mixing my own glazes. I needed a red glaze and spent $20 for a pint and spending $7+ for a pint of glaze is prohibitive if you are trying to make a profit. I will admit that buying a small amount for a few pieces is easier than mixing your own.
I'm glad to see most of the chemicals I have chosen are on the list you provided as "safer". I have 2 cats and 2 dogs who frequently run around in my studio (which I appreciate this time of year to keep the field mice from coming into it - my dogs are mousers...go figure). I don't purchase large quantities of chemicals since I don't want them laying around...what I do have are double bagged and kept in a plastic cupboard...my chemical cupboard. I've never received an MSDS sheet for any of the 25 chemicals I have. Chrome Oxide..being one I now need to do more research on since it is in 2 of my favorite glazes.
I try to only use glaze recipes that have been listed as stable. I don't have the chemical background knowledge to start mixin and matchin and who knows what I might release. There is a local supplier (I don't buy from her unless it's an emergency) and she told me the local schools only buy commercial glazes now because of the research that some of the chemicals can make men infertile. I was thinking...hmmm ok...but what about the dangers of all the other chemicals via ingestion, dust etc.....
I turn to this site alot when it comes to my glazes. I search the archives and if I can't find it, I'll ask...even though it may be something that was hashed over a year ago but I missed it. I recommend this site to every potter I meet either in person or via the internet or whatnot. It is full of the best information.
Nancy
Hilltop Pottery
Lili Krakowski wrote: Cliff: You are on the right track. You are calculating your glazes and
figuring out what actually is in them. Not essential as good glazes were
made for centuries before Hermann Seger came along, but today calculating is
a welcome "shortcut" to knowledge about glaze stability. (And, Roy, still
got my slide-rule in the studio...)
The weather is dreadful, AND the chiropractor warned me to give my shoulders
a rest for a few days, so I recalculated Cliff's glaze.
I cannot get Gerstley Borate, many others can't either, and I hated the
stuff when it was around. Here I used frits.
Frit 3195 21.8
Frit 31.85 23.9
Dolomite 12.7
Kaolin 12.9
Whiting 12.6
Flint l6.1
The formula looks like this:
Na2O .141
K2O .002
MgO .184
CaO .673
Al2O3 .201
B2O3 .559
SiO2 2.024
And the COE is 68.06. Both the alumina and silica are within the "limits"
as is the COE. There is a little bit more soda, and a little less boron. I
doubt that will matter.
I think, Cliff, you might want to read ABOUT the materials in as many books
as you can find. Interloan at your Public Library will get you lots of
good books. Many materials are listed as fluxes, for instance, but that does
not mean they necessarily act the same way, esp. with finishes (shiny,
satiny) and with color. I might add I was astonished a few days ago that
a fellow ClayArter was not familiar with the Internet used book sellers:
Biblio, Abebooks, Alibris, AddAll..and there may be more. But these sellers
keep me from illiteracy....
Back to clay. This AM I read this recipe on ClayArt:
>> Neph Sy 120
>> Lithium Carbonate 65
>> Whiting 15
>> Barium Carb 115
>> Ball clay 15
>> Flint 155
>> Frit 3124 50
>> Chrome OX 2.5
whose formula turns out to be:
LiO2 .409
Na2O .113
K2O .029
CaO .174
BaO .273
Al2O3 .152
B2O3 .046
SiO2 1.925
With a COE 78.99
The alumina and silica are below the limits. I would think this an
unstable glaze. Then it contains BARIUM, which, thank goodness, the clay
community now agrees is a no-no. Then there is lithium--12.5% of , which is
high. And then there is, the chromium.
Last week we had another go-around on lithium. Edouard Bastarache told us
none of the professional literature mentions any case of someone being
poisoned by accidental ingestion of lithium. I do not doubt this, at all.
But I do not know whether a regular MD or Emergency Room, getting in a
bi-polar patient on lithium meds, and with overdose symptoms would realize
this was not a suicide attempt, nor badly adjusted meds, but getting lithium
into the system from lithium dust in the studio. And even if they did
realize it, would they necessarily report it to "the professional
literature."
And then the chromium--about which Monona Rossol has a bit to say in the
May/June/06 CLAY TIMES .
What concerns me so very much is glaze recipes like the above being "out
there". An occupational therapist, a school teacher, just a plain "newbie"
can get lithium, barium, chrome without any warning label on the bags. Oh
sure, you are supposed to get MSDS sheets with the materials--but one does
not when buying in very small quantities. And even in a school or similar
where materials are bought in 50 lbs sacks, MSD sheets supplied, does
everyone read them? Does everyone who handles the materials have a properly
fitted mask? Shower and shampoo and put on fresh clothes when the weighing
out and mixing has been done? I will not go on, you get the picture.
Some years ago Monona Rossol published in her CT column the findings of one
Lynn Barth who went to a great deal of trouble to make up a list of Safer
Glaze Ingredients and Safer Colorants and Opacifiers.
Bone Ash
Dolomite
Kaolin and Other Clays
Magnesium Carbonate
Nepheline Syenite
Potassium and Sodium Feldspars
Whiting
Wollastonite
Copper Oxides
Iron Oxides and Ilmenite
Tin Oxide
Titanium Oxide and Rutile
Zinc Oxide
Zirconium Silicate
Monona cautions that mined substances often are contaminated with other
materials and the material data sheet should be read.
Concern IS out there. I cannot imagine that "we" cannot think up a way to
protect newbies, who do not "question" recipes,
who think any nice white powder is like flour or sugar; school teachers
and therapists who just are not sufficiently informed;
janitors who sweep and mop up spills and wipe counters without masks and
other precautions because no one told them...
Could we not think of some way? We live by our ideas...let's think
something up.
Lili Krakowski
Be of good courage
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