Les Lowe on wed 15 jan 97
Hi,
Recently there have been a lot of glaze recipes for ^6, but no one has
specifically said whether they were safe for food containers or not. Could
someone please fill me in?. Thanks.
^6-10 oxidation navy blue
albany slip 80 - is albany slip food safe?
gerstley borate 20
cobalt carb. 5% - what is the maximum % for this to a glaze?
^6 oxidation [^7 in sitter] from ClayTimes
Neph sy 47.3
gerstely borate 27.0
silica 20.3
EPK 5.4
100.0
Add:
*red iron oxide 2.0
*cobalt oxide 1.0
*rutile 4.0
*bentonite 2.0
* -I'm not sure about these
Black ^6 oxidation [^7 in sitter] from Brian Kemp off Clayart
potash feldspar 42
silica 26
whiting 15
kaolin 15
*zinc oxide 12
*red iron oxide 8
*cobalt oxide 1
Mild day here in Alberta, sure is nice after the cooold weather!
Linda
Tony Hansen on thu 16 jan 97
> Recently there have been a lot of glaze recipes for ^6, but no one has
> specifically said whether they were safe for food containers or not.
Each recipe needs to be considered on its own merits. There are many things we d
know but some that we do and it is surprising what a little common sense can do
to help you decide what is safe.
Check the web page at http://digitalfire.com/magic/articles/leaching.htm
for an overview.
--
=================================================================
Tony Hansen, IMC - Publishers of INSIGHT/FORESIGHT/Magic of Fire
Ron Roy on sat 18 jan 97
>Recently there have been a lot of glaze recipes for ^6, but no one has
>specifically said whether they were safe for food containers or not. Could
>someone please fill me in?. Thanks.
>
>^6-10 oxidation navy blue
>albany slip 80 - is albany slip food safe?
>gerstley borate 20
>cobalt carb. 5% - what is the maximum % for this to a glaze?
When I calculated this glaze with the B2O3 included in flux unity it was a
little short of silica. I would say add 5 parts of silica to be sure it is
durable.
Most texts sat 1% Cobalt (I think they mean the oxide) is enough to give a
very strong blue. They also say cobalt is a strong flux. Could not find a
reference to the maximum amount.
>^6 oxidation [^7 in sitter] from ClayTimes
>
>Neph sy 47.3
>gerstely borate 27.0
>silica 20.3
>EPK 5.4
> 100.0
>
>Add:
>*red iron oxide 2.0
>*cobalt oxide 1.0
>*rutil 4.0
>*bentonite 2.0
>* -I'm not sure about these
I think this glaze is durable the way it is.
>Black ^6 oxidation [^7 in sitter] from Brian Kemp off Clay
>
>potash feldspar 42
>silica 26
>whiting 15
>kaolin 15
>*zinc oxide 12
>*red iron oxide 8
>*cobalt oxide 1
This glaze is oversupplied with Zinc so I suspect the durability would not
be good.
I calculated these glazes without the colossus added but I don't think they
are a problem in terms of glaze stability.
It is not so hard to test durability. My alkaline test is to leave a glazed
tile in the dishwasher and check it against a control tile every week. The
real test is harder - immerse in 5% solution of washing machine agent for a
minimum of 32 hours at 76C +or - 2C. The acid test is - immerse tile in
acetic acid for 16 hours at room temp. - then compare with control tile.
Results will vary from - no effect - to no gloss left.
It will be informative to use stains - like ink or food stains - to make
imperfections stand out - some times the chemical attack is not even and
results can be patchy. Gloss measurement however is a useful and accurate
method of assessing glaze resistance to chemicals
A good magnifier will help you see what's been going on - the one I use I
bought at a stamp store for about $10. Its a little over 1.25 inches wide
and 1.75 long - Plastic & tear drop shaped. It has two fold out lenses. One
lens enlarges by 4 and the other by 6 - together by 10. Those of you who
have never looked at a glaze under magnification will be amazed at how
helpful a close look is when you are trying to figure out what is really
going on.
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
Ron Roy on sun 19 jan 97
Whoops - my spell checker is playing tricks on me again!
>I calculated these glazes without the colossus added but I don't think they
>are a problem in terms of glaze stability.
Should be "without the colours added"
No excuse for the following - must have been taking a nap.
>The acid test is - immerse tile in
>acetic acid for 16 hours at room temp. -
Should read - immerse tile in a 5 percent solution of acetic acid for 16
hours at room temp for ...
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
Sandi Southwell on fri 19 feb 99
Hi everyone. I'm new to this group and would really appreciate any help
anyone could give me. I am interested in obtaining wome very dependable
^6 oxidation glaze recipes. I know this has probably been mentioned
before but I need to find a few glazes that I can use all the time. To
start light, medium, and dark blue as well as white, clear, black,
green, and brown are some basic colors I am interested in. As well this
semester at Gaston College (Dallas, NC), my focus is to make ^6
majolica. I would appreciate any help in obtaiing a good glaze as well
as a good clay body that is as close to white as possible that I could
use interchangably for ^6 stoneware. Any help would be appreciated.
Thanks.
Sandi Southwell.
Jan Adams on fri 19 feb 99
Sandi,
I did some work with ^6 majolica a few years ago and I'll be glad to
talk with you about that. Also want to let you know about the potters in
Catawba and surrounding counties. As you didn't include your address,
contact me if you're interested. Jan at Mountain View Pottery in Hickory,
NC
Earl Brunner on sat 20 feb 99
There are a couple of things you can do. There are several places that past
postings to this list are archived and there are many postings on the
subject. However, I would recomend that you go to www.Digitalfire.com and
check out their material on cone 5-6.
Tony Hansen suggests if I'm not mistaken, that rather than skip around
trying formulas from who knows where(not that that matters much), but its a
shotgun approach. Instead, focus on one or two glazes with good
characteristics and manipulate the colorants in them to get you variations.
Good Luck
Earl Brunner
Sandi Southwell wrote:
> ----------------------------Original message----------------------------
> Hi everyone. I'm new to this group and would really appreciate any help
> anyone could give me. I am interested in obtaining wome very dependable
> ^6 oxidation glaze recipes. I know this has probably been mentioned
> before but I need to find a few glazes that I can use all the time. To
> start light, medium, and dark blue as well as white, clear, black,
> green, and brown are some basic colors I am interested in. As well this
> semester at Gaston College (Dallas, NC), my focus is to make ^6
> majolica. I would appreciate any help in obtaiing a good glaze as well
> as a good clay body that is as close to white as possible that I could
> use interchangably for ^6 stoneware. Any help would be appreciated.
> Thanks.
> Sandi Southwell.
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