Mary Higgins on sat 25 nov 00
Dear fellow clayarters:
I have The Potter's Palette, by Christine Constant and Steve Ogden. One
of the base glazes in the book is the following:
Lead Glaze Cone 04
Lead bi-silicate 65
Whiting 10
Potash Feldspar 15
China Clay 10
The authors suggest using a borax frit instead of the lead bi-silicate
if desired. My question is, which frit? I have some 3134. Will it do?
Also, could Neph. Sye. be used instead of the potash feldspar without
being too much of a problem? I know there are other borax frits
available. Is this a stable glaze for food surfaces (without the lead)
if one does not add too much oxide? I am a newbie and would appreciate
any input from those of you who know a lot about formulating glazes.
Thank you in advance.
Mary in Polk County, Florida
Where the rainfall is 18 inches below normal for the year.
Wade Blocker on sun 26 nov 00
Mary,
In an article which appeared in Ceramics Montohly January 1993,p.83 the
following was listed as a substitute for lead:
white lead:
10% neph syenite plus 10%Borax
or Pemco frit 25 plus 10% borax
Do not use lead in your glazes- ever. Lead is poisonous and it infects your
kiln for future firing. Mia in ABQ
Ababi Sharon on sun 26 nov 00
Try to take a majolica base, without tin/ultrox, it might be good for you.
Ababi
----- Original Message -----
From: "Wade Blocker"
To:
Sent: Sunday, November 26, 2000 8:36 PM
Subject: Re: Cone 04 glaze base
> Mary,
> In an article which appeared in Ceramics Montohly January 1993,p.83 the
> following was listed as a substitute for lead:
> white lead:
> 10% neph syenite plus 10%Borax
> or Pemco frit 25 plus 10% borax
>
> Do not use lead in your glazes- ever. Lead is poisonous and it infects
your
> kiln for future firing. Mia in ABQ
>
>
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>
pedresel on mon 27 nov 00
Very timely. I just tested several low fire glazes this weekend,
including the one John Hesselberth recommended. That one ended up milky
with bubbles for me, although perhaps I got it a little thick. My best
tests were:
Low fire clear ^04 (tested at ^03)
(from Beverly Crist on Clayart quite a while ago)
Ferro Frit 3134 60
OM4 Ball Clay 40
Woody's Base ^04 (tested at ^03)
(Woody Hughes via Ceramics Monthly/Clayart)
Gerstley Borate 26
Nephelene Syenite 20
Ferro Frit 3124 30
Lithium carbonate 4
Kaolinite (EPK) 10
Flint 10
Both fired to a smooth surface with some bubbles visible where thick.
Both survived 3 freeze-boil cycles (incidentally, my clay body also
survived just fine although that is I suppose no guarantee of
frost-proof ware). I use Seattle Pottery Supply terra cotta with sand.
Disclaimer, I haven't tested these with colorants or for leaching, nor
have I run them through a glaze calculation program. I can only trace
the pedigree of these back so far so sorry if I didn't give credit to
the appropriate originator.
Although RR seems to prefer glazes with many ingredients, the first one
is attractive since I won't have to work on substituting for the
gerstely borate and some people might object to the lithium. I suppose
I'll test both with colorants anyway.
Good luck and as always, your mileage may vary.
-- Evan in W. Richland who left work at 4:15 and had to walk the dogs in
the dark. Stella wore her yellow reflector collar with a red flashing
light and Temmi had her orange vest with reflective stripes and a
high-tech collar with flashing white stripe and a red flashing light. I
wore my Illuminite reflective vest so we must have been quite the sight
(that was the idea, anyway). Still some drivers on my dark road zoomed
by with out moving over an inch. Most were good though. Suppose I
should have worn my headlamp, too.
Oh yeah, 18 inches is nearly 3 times our average annual rainfall.
Mary Higgins wrote:
>
> Dear fellow clayarters:
>
> I have The Potter's Palette, by Christine Constant and Steve Ogden. One
> of the base glazes in the book is the following:
>
> Lead Glaze Cone 04
>
> Lead bi-silicate 65
> Whiting 10
> Potash Feldspar 15
> China Clay 10
>
> The authors suggest using a borax frit instead of the lead bi-silicate
> if desired. My question is, which frit? I have some 3134. Will it do?
> Also, could Neph. Sye. be used instead of the potash feldspar without
> being too much of a problem? I know there are other borax frits
> available. Is this a stable glaze for food surfaces (without the lead)
> if one does not add too much oxide? I am a newbie and would appreciate
> any input from those of you who know a lot about formulating glazes.
> Thank you in advance.
>
> Mary in Polk County, Florida
> Where the rainfall is 18 inches below normal for the year.
John Hesselberth on mon 27 nov 00
Mary Higgins wrote:
>The authors suggest using a borax frit instead of the lead bi-silicate
>if desired. My question is, which frit? I have some 3134. Will it do?
>Also, could Neph. Sye. be used instead of the potash feldspar without
>being too much of a problem? I know there are other borax frits
>available. Is this a stable glaze for food surfaces (without the lead)
>if one does not add too much oxide? I am a newbie and would appreciate
>any input from those of you who know a lot about formulating glazes.
>Thank you in advance.
Hi Mary,
Using 3134 in place of the lead in the recipe you quoted will most likely
not give you a stable glaze. The silica level will be quite low at 1.6
(you should aim for 2.5 or above. The alumina level will also be quite
low at 0.14 (you should aim at .25 or above). This means the boron level
will have to be fairly high in order to get it to melt.
I have not worked much with low fire glazes; however I do know that the
window for obtaining stable glazes is much, much smaller than it is at
cone 6 and above. At cone 04 it is very difficult to get enough silica
and alumina to give a stable glaze and still get it to melt.
A cone 04 glaze that I have tested a little bit also comes from Potter's
Palette and seems quite stable. It is:
Frit 3124 75
EPK 15
Flint 10
You will still need to have it leach tested to be certain it is stable
with whatever colorants you put in it. We just don't have enough
information yet to be able to predict stability.
Good luck. If you do test it how about letting us know the results so we
can all learn.
John Hesselberth
Frog Pond Pottery
P.O. Box 88
Pocopson, PA 19366 USA
EMail: john@frogpondpottery.com web site: http://www.frogpondpottery.com
"It is, perhaps, still necessary to say that the very best glazes cannot
conceal badly shaped pots..." David Green, Pottery Glazes
Ron Collins on wed 29 nov 00
Evan....I am glad you did the glaze test...I tried it myself this
afternoon..was looking for a simple clear that doesn't craze on my clay and
doesn't use silica. ...60 3134 and 40 OM4
-it's milky ivory, but is nice and doesn't craze...
I use local earthenware with additions. Could be clear enough if thin.
Think I will mix up a batch with the last of my 3134. Let me know when you
do oxide/colorant/tin tests and I'll see if I get the same...are you firing
ox. or neutral in gas? Melinda in sunny Guatemala where my studio's outside
and it's spring all year round...
John Hesselberth on wed 29 nov 00
pedresel wrote:
>
>Low fire clear ^04 (tested at ^03)
>(from Beverly Crist on Clayart quite a while ago)
>
>Ferro Frit 3134 60
>OM4 Ball Clay 40
Hi Evan,
I'm sorry to hear the glaze I suggested didn't work well for you. I
tested it with copper carbonate in it and it did fine.
The above glaze is probably reasonably stable. It has silica at 2.5 (the
minimum I like to see) and alumina at 0.33. It may well hold moderate
levels of colorants fairly well.
I'll be interested to hear if anyone tests it with colorants and, in
particular, if you vinegar or leach test it.
Regards, John
John Hesselberth
Frog Pond Pottery
P.O. Box 88
Pocopson, PA 19366 USA
EMail: john@frogpondpottery.com web site: http://www.frogpondpottery.com
"It is, perhaps, still necessary to say that the very best glazes cannot
conceal badly shaped pots..." David Green, Pottery Glazes
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