Candice Roeder on mon 1 jul 96
Hello Clayarters:
I have been off-line for several days (art fair a'comin') and upon
retrieving my e-mail found several of you interested in my recipe for a cone
6 clear glaze that worked well (for me, anyway) over underglazes. (Sorry for
the delay) It works over the Amaco Reward Velvet Underglazes, including
reds, purples, etc. I will post the original recipe and then add my
revisions.
SG-42 Clear Semi-mat Glaze (is glossy for me...) Cone 6 (o.k. cone
5-7) Chappell
Pemco Frit #626 ..........21.4
Neph Sy......................24.8
Wollastonite................14.4
Whiting....................... 4.8
EPK Kaolin............... 7.1
Silica ........................ 31.5 (I originally used 325 mesh Flint)
Add:
Bentonite....................2.0
C.M.C........................1 tsp.
OK. The above glaze crazed on my A.R.T. #135 porcelain at cone 6. Being
absolutely non-technical, I stumbled in to the following substitution: I
substituted calcined kaolin (comercial name Glomax, from A.R.T.) for the
EPK. I also substituted Amorphous Silica for the Flint. I don't use
C.M.C. I do add Flocs...it settles out. I believe, somewhere in my
past, Richard Burkett told me the changes I made shouldn't have made the
difference, but, it did...go figure...
It is glossy and very clear. My samples from two/three years ago still look
good, no delayed crazing. I don't use it on anything, because I found a
whole palette of glazes while I was looking for a good clear, and have lost
interest in underglaze decorating. The pursuit was interesting, though ;-)
I found the Pemco Frit 626 through Trinity supply in Texas. I do not know
about substitutes.
Good luck.
Candice Roeder
Watching the swans on the lake in summery Michigan
Tony Hansen on fri 5 jul 96
Candice Roeder wrote:
>SG-42 Clear Semi-matt Glaze Cone 6 (Chappell)
>....
>Pemco Frit #626.....21.4
>....
I guess I've watched long enough to get up the courage to say something.
Candice, I could be wrong, but I think Frit 626 has 12% barium. It is
equivalent to Ferro 3289 and Fusion F-65. Barium is barium, and 12% is a
fair bit. I don't understand the full danger of barium but I do know it
is in the middle of a controversy and some pretty knowledgable people
have pointed an accusing finger at it here. Besides, unless there is a
compelling reason for barium (i.e. a crystal matte, a difficult color
response) why use it? A glossy clear glaze can be made easily with other
oxides. I've had good success with #G1214L: 27 Frit 3134, 20
Wollastonite, 22 EPK, 23 Flint, 7 CusterSpar.
Trepidatiously Yours,
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Tony Hansen, IMC, 134 UPLAND DRIVE, Medicine Hat, Alberta
T1A 3N7 Canada Phone:403-527-2826 FAX:527-7441 BBS:527-6074
email: thansen@mlc.awinc.com web: http://digitalfire.com/imc.html
Candice Roeder on fri 5 jul 96
At 04:13 PM 7/5/96 +0000, you wrote:
>----------------------------Original message----------------------------
>Candice Roeder wrote:
>>SG-42 Clear Semi-matt Glaze Cone 6 (Chappell)
>>....
>>Pemco Frit #626.....21.4
>I guess I've watched long enough to get up the courage to say something.
>Candice, I could be wrong, but I think Frit 626 has 12% barium. It is
>equivalent to Ferro 3289 and Fusion F-65. Barium is barium, and 12% is a
>fair bit. I don't understand the full danger of barium but I do know it
>is in the middle of a controversy and some pretty knowledgable people
>have pointed an accusing finger at it here. Besides, unless there is a
>compelling reason for barium (i.e. a crystal matte, a difficult color
>response) why use it? A glossy clear glaze can be made easily with other
>oxides. I've had good success with #G1214L: 27 Frit 3134, 20
>Wollastonite, 22 EPK, 23 Flint, 7 CusterSpar.
Tony,
I wondered, when I was asked for the recipe, who would be the first to jump
on this. I don't use the glaze, since, as I stated, have moved onto other
things, but it does work well. If you don't want to use it then DON'T. Or
use another glaze as a liner and use this one on the outside. Or, one could
just take note of the high calcium content, and the lack of boron, magnesium
and zinc, and take those as cues to what makes for good color development
when using stains. Sounds like I know something technical doesn't it....NOT.
As far as the recipe goes, I quote from the book here "Pemco Frit #626. A
nontoxic barium silicate frit used in earthenware and lower-temperature
stoneware glazes. Substitute: Hommel frit #400........" "...Due to its
toxic nature, the author suggests that it (barium) be used only in the frit
form, which is not toxic"....."...In today's health-conscoius atmosphere, it
is hightly significant that the recipes offered in this book are nontoxic.
More and more potters are concerned about the health hazards associated with
their craft and will welcome the wide range of safe clays and glazes
gathered in one indispensable resource."
One could say that the above quotes are misleading, if, in fact, the frit is
not safe, yes?? What is the poor non-technical person to do? When in
doubt, don't use it.
Sorry if I have mislead anyone here.
Candice Roeder
"
>
>Trepidatiously Yours,
>-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
> Tony Hansen, IMC, 134 UPLAND DRIVE, Medicine Hat, Alberta
> T1A 3N7 Canada Phone:403-527-2826 FAX:527-7441 BBS:527-6074
>email: thansen@mlc.awinc.com web: http://digitalfire.com/imc.html
>
Tom Buck on sat 6 jul 96
As an Alberta potter discovered, just put vinegar in a bowl glazed with a
recipe containing the barium frit and let sit for 12+ hours. If the glaze
surface takes on a slight milky hue, then the acid in the vinegar is
reacting with the alkaline earth ions (barium ions mainly). And this pot
should not be used with food. Of course, one could have accurate leach
tests done and determine the actual release of barium ion from the glaze;
any release close to 1 microgram/millilitre (1 part per million) would make
the pot hazardous for frequent use.
TomB Hamilton Canada
PEDresel@aol.com on sun 7 jul 96
Tony Hansen Wrote:
----------------------------Original message----------------------------
Candice Roeder wrote:
>SG-42 Clear Semi-matt Glaze Cone 6 (Chappell)
>....
>Pemco Frit #626.....21.4
>....
I guess I've watched long enough to get up the courage to say something.
Candice, I could be wrong, but I think Frit 626 has 12% barium. It is
equivalent to Ferro 3289 and Fusion F-65. Barium is barium, and 12% is a
fair bit. I don't understand the full danger of barium but I do know it
is in the middle of a controversy and some pretty knowledgable people
have pointed an accusing finger at it here. Besides, unless there is a
compelling reason for barium (i.e. a crystal matte, a difficult color
response) why use it? A glossy clear glaze can be made easily with other
oxides. I've had good success with #G1214L: 27 Frit 3134, 20
Wollastonite, 22 EPK, 23 Flint, 7 CusterSpar.
---------------- End included message (Include complaint about AOL mail)
------
According to my Georgies Ceramic Supply catalogue (free plug for a company
that puts this sort of useful information in their mailings) these frits are
equivalent.
However, the chart says that Ferro 3289 contains 27.4 % of BaO which would be
24.5 % barium (ok so I needed my College intro text and a calculator to
figure that
out).
I don't use barium in glazes anymore. I am very sceptical about the actual
risk either from barium carbonate or from leaching glazes, but why bother?
The only thing is that
I'm also sceptical that strontium is as benign as people consider it...
-- Evan Dresel
In Eastern WA USA where we are having a particularly bad brush-fire season
pedresel@aol.com
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