Assumption Abbey on fri 18 dec 98
Dear Readers:
I am searching for a cone 9 - 10 glaze that would incorporate both Titanium
dioxide and Zinc that I might try in reduction on stoneware and porcelain
bodies. Thanks in advance.
Llewellyn Kouba
ABBEY POTTERY
Ruth Radin on sat 19 dec 98
Are you looking for a crystalline glaze?
Ron Roy on sat 19 dec 98
Hi Llewellyn,
No point in putting ZnO in a reduction glaze - it is easily reduced and
volatilize off - several on this list have omitted it from their reduction
glazes and could not discern a difference with it gone.
>----------------------------Original message----------------------------
>Dear Readers:
>
>I am searching for a cone 9 - 10 glaze that would incorporate both Titanium
>dioxide and Zinc that I might try in reduction on stoneware and porcelain
>bodies. Thanks in advance.
>
>Llewellyn Kouba
>ABBEY POTTERY
Ron Roy
93 Pegasus Trail
Scarborough, Ontario
Canada M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
Web page: http://digitalfire.com/education/people/ronroy.htm
Assumption Abbey on sun 20 dec 98
At 14:51 12/19/98 EST, you wrote:
>----------------------------Original message----------------------------
>Are you looking for a crystalline glaze?
>-------
Dear Ruth,
Yes, this could be a crystalline glaze I suppose. What I became interested
in quite some time ago was a glaze (Type) that Bill Cambell Studio uses..
not as a copy but a a take off point in discovery of self. He had an
article in Ceramic monthly some time ago and I did write to him and he
suggested I might try a titanium/zinc glaze. I am very fond of the
greens/blues/ translucent colors /smooth and all this is on sort of a dark
ground (slip) and the color sings. I have success with some dark slips and
am still trying to work my slow way up to some kind of rich surface. I am
not writting from my studio so not sure which issue this type of work was
shown but I think it is one that is both elusive and has a very (low?) melt
and might be run easily and or colors go out the flue if not done properly.
I don't know if this is a help to my quest and I realize it may take years
to (practice) and get it right but that is part of the fun and learning.
Thanks
Llewellyn
Jim Brooks on mon 21 dec 98
Ron Roy.. at what temp does zinc oxide volatize could this glaze be used at
cone 6?.. or less ...?x
Michael McDowell on mon 21 dec 98
In response to a request for a high fire reduction glaze using both titanium
and zinc oxide, Ron Roy wrote:
"No point in putting ZnO in a reduction glaze - it is easily reduced and
volatilize off - several on this list have omitted it from their reduction
glazes and could not discern a difference with it gone."
This is indeed the conventional wisdom on the subject, but I feel I must
dispute it, or at least offer some contrary anecdotal experience. I've really
made little use of Zinc Oxide in glazes, but years ago when I was actively
exploring the uses of Mt. Saint Helens Volcanic Ash in glazes I for some
reason decided to use 10% additions of Zinc oxide and Titanium oxide as
opposite poles in a Triaxial blend with straight Mt. St. Helens ash. Not that
the results were incredibly nice or anything, but there was definitely a
discernible effect from the Zinc oxide. Now at the time I was only doing a
reduction phase at the end of my firing. I didn't do the earlier "body
reduction". My guess is that the zinc was able to affect the melt prior to the
time that I subjected it to a reduction atmosphere which may well then have
evaporated it. Or perhaps the melt had already proceeded to the point that the
zinc was effectively held in the matrix of the glass so that not all of it
could volatilize. In any case, it's inclusion in the batch was clearly
contributing to the final result.
Llewellyn Kouba, yours was the original request. I am wondering "Why?" Have
you got some cheap source of these two ingredients in combination? Or is it
just a lark? Like I said, my results were not great, and they are probably
dependent on a rather unusual reduction regime. But if you have a burning need
to know, I'd be happy to share what I can recall if you contact me directly.
Michael McDowell
Whatcom County, WA USA
mmpots@memes.com
http://www2.memes.com/mmpots
Patricia & John Richmond on tue 22 dec 98
------------------
Glaze =9010-11
Sodium silicate 50cc
Silica 25g
Zinc Oxide 25g
Titanium Oxide 5g
Glaze =90 8-10
Feldspar 75
Borate frit similar to pure colemanite 40
Zinc Oxide 35
You may also want to look in the literature for Marc Hanson. During the late
60's and 70's, he produced remarkable glazes.
=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F
Patricia =26 John Richmond
richmoj=40worldnet.att.net
Daytona Beach, Florida 32119
=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F
Tom Buck on tue 22 dec 98
Hi:
You asked Ron Roy for the boilding point of Zinc Metal. I'll save
Ron R a lookup - my trusty Handbook of Physics and Chemistry says Zinc
Metal boils at 907 degress Celsius (1665 oF) under normal atomspheric
pressure. This is Cone 010/011 range. So skip C6 reduction firings for any
glaze with some Zinc Oxide in it. Or skip the Zinc Oxide in the glaze.
Happy holidays. Peace. Tom.
Tom Buck ) tel: 905-389-2339
& snailmail: 373 East 43rd St. Hamilton ON L8T 3E1 Canada
(westend Lake Ontario, province of Ontario, Canada).
Ron Roy on wed 23 dec 98
Thanks to Tom for helping on this - Hamer says ZnO is easily reduced - even
slight reduction above 925C will eliminate it from the glaze. To answer the
question - will it stay in a reduced cone 6 (1200C) glaze - the answer must
be no. Besides this it is not an active flux below 1085C. From this it
could be surmised that it is not useful as a glaze flux in reduction at any
temperature.
It makes sense to me that if it is not reduced until the end of a firing
that goes above 1085C that it will help the melt and therefore will have
some effect - I also have to assume that if reduced at the end at least
some of it will be lost and this will have some effect on the durability
and the expansion of the glaze.
It is an easy point to prove - mix up any reduction glaze with and without
ZnO and fire them together in a reduction atmosphere.
I wonder how much all that Zinc, in all those reduction glazes, over all
the years, cost? The current price for ZnO up here is about $5 per lb.
I just did a quick survey of my books and found only 4 references to this.
Hamer - as I have stated already is where I first found it - Out of the
Earth Into the Fire by Mimi Obstler mentions the Hamer reference, Cardew in
Pioneer Pottery says it happens and Ian Currie in his Stoneware Glazes says
on page 39 "When the zinc set is fired in strong reduction, zinc oxide
seems to disappear without a trace."
I recommend all of the above books The Hamer, Currie and Obstler books are
still in print.
The Cardew book is a gem but out of print - there is talk of having it
legally reprinted - anyone interested in a copy or copies should let me
know and I will advise the cost per copy when we know more -
I have a lot of books - about 50 and this aspect of ZnO is simply not
included in great majority of them - makes me wonder - what else is
missing? Can anyone else find any references?
>----------------------------Original message----------------------------
>In response to a request for a high fire reduction glaze using both titanium
>and zinc oxide, Ron Roy wrote:
>
>"No point in putting ZnO in a reduction glaze - it is easily reduced and
>volatilize off - several on this list have omitted it from their reduction
>glazes and could not discern a difference with it gone."
>
>This is indeed the conventional wisdom on the subject, but I feel I must
>dispute it, or at least offer some contrary anecdotal experience. I've really
>made little use of Zinc Oxide in glazes, but years ago when I was actively
>exploring the uses of Mt. Saint Helens Volcanic Ash in glazes I for some
>reason decided to use 10% additions of Zinc oxide and Titanium oxide as
>opposite poles in a Triaxial blend with straight Mt. St. Helens ash. Not that
>the results were incredibly nice or anything, but there was definitely a
>discernible effect from the Zinc oxide. Now at the time I was only doing a
>reduction phase at the end of my firing. I didn't do the earlier "body
>reduction". My guess is that the zinc was able to affect the melt prior to the
>time that I subjected it to a reduction atmosphere which may well then have
>evaporated it. Or perhaps the melt had already proceeded to the point that the
>zinc was effectively held in the matrix of the glass so that not all of it
>could volatilize. In any case, it's inclusion in the batch was clearly
>contributing to the final result.
Ron Roy
93 Pegasus Trail
Scarborough, Ontario
Canada M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
Web page: http://digitalfire.com/education/people/ronroy.htm
Ron Roy on wed 23 dec 98
Hi Jim,
While I was doing the research for my other post on this there were
comments about it being volitile even in oxidation.
You can some times see this on the clay where it is close to the glaze.
This may also be due to some small amount of reduction - it's not all that
clear in the texts. Your might just put some ZnO in a small test bowl and
see what happens.
RR
>----------------------------Original message----------------------------
>Ron Roy.. at what temp does zinc oxide volatize could this glaze be used at
>cone 6?.. or less ...?x
Ron Roy
93 Pegasus Trail
Scarborough, Ontario
Canada M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
Web page: http://digitalfire.com/education/people/ronroy.htm
Earl Brunner on thu 24 dec 98
All of this discussion about zinc has got me thinking, I have this glaze that I
really like, It's a very dry matt glaze, from the barium most likely. I really
like it's responses and blushes of clor from oxides, especially copper, and it
gives great effects with some wood ash sprayed lightly over it, in fact, I reall
don't like the glaze at all unless it has wood ash sprayed over it.
The glaze is fired to cone 10 in reduction with reduction beginning around 1700
and has 8.8% zinc in it, I think that I had heard/read that zinc volitized, but
didn't make this glaze formula and just assumed that it must be contributing
SOMETHING? This is the emperical formula for the glaze:
Na2O 0.14
K2O 0.09
CaO 0.31
ZnO 0.28
BaO 0.18
Al2O3 0.41
SiO2 1.86
It would be anybody's guess what the actual formula would be after the ash is
sprayed on and combined in the melt. I use unwashed barbecue grill charcoal ash
Since connecting to clayart, I've become more conserned about barium, but most o
my peices are more sculptural and less functional. So generally the barium cont
would not be a problem for me. I'm wondering if I need to reformulate this Glaz
Earl Brunner
Ron Roy wrote:
> ----------------------------Original message----------------------------
> Thanks to Tom for helping on this - Hamer says ZnO is easily reduced - even
> slight reduction above 925C will eliminate it from the glaze. To answer the
> question - will it stay in a reduced cone 6 (1200C) glaze - the answer must
> be no. Besides this it is not an active flux below 1085C. From this it
> could be surmised that it is not useful as a glaze flux in reduction at any
> temperature.
>
> It makes sense to me that if it is not reduced until the end of a firing
> that goes above 1085C that it will help the melt and therefore will have
> some effect - I also have to assume that if reduced at the end at least
> some of it will be lost and this will have some effect on the durability
> and the expansion of the glaze.
David Hendley on fri 25 dec 98
Well, Llewellyn,
after all this discussion about zinc oxide in a reduction
glaze, did you ever get any glaze recipes?
Here is a cool glaze that has been around for at least 30 years.
I've seen it under 2 different names, Porcelain White,
and Martha's White.
I think I got Porcelain White in 1972 from my first pottery
teacher, Clayart's own Tracy Dotson.
This glaze is NOT a balanced glaze. It is actually over-fired
at cone 10, but that's what makes it fun. It will change from
a soft off-white semi-gloss (a little cool) to a wild blue/purple
runny glaze with small white crystals (a little hot). If your
kiln has a 'hot spot', try it there for some really gaudy effects.
It WILL run, so use it on the top third of a pot only, or use a
biscuit on the bottom of the pot, or be sure your kiln shelves
are protected.
Don't even mix it up if you are in a school situation where
others will be using it.
I don't know if the zinc oxide is really doing anything in this
glaze. I haven't used it in years or done any tests with it. It
would be an interesting test to mix up a batch with and without
the zinc.
Porcelain White ^10 reduction
40 Soda feldspar
30 flint
30 whiting
15 kaolin
10 zinc oxide
10 titanium oxide
David Hendley
Maydelle, Texas
hendley@tyler.net
http://www.farmpots.com
Tom Buck on fri 25 dec 98
Earl:
With you spraying a raw wood-ash wash onto top of your original
glaze (BaO/CaO/KNaO/ZnO + Al2O3 and SiO2) you are likely doing two things,
1) adding more KNaO and SiO2 to the underlying glaze; and 2) Making the
glaze shift into a C10 range as a "balanced" mix (or nearly so). It
becomes a Barium/Calcium - Alumina dry matt with enough silica to hold it
all together.
Do you need the Zinc Oxide? No! In good reduction it will not be
in the final glaze coat, although it possibly may have in some way helped
make the mix more fusible and hence stable.
I suggest you try the following mix:
15 Barium carbonate
11 Whiting
43 Kona F-4 fs (or other soda spar)
17 G-200 fs or Custer fs
14 EPKaolin
Mix it as is then take a portion and add approx. 8+% Zinc Oxide, then fire
the two side by side and see if the ZnO does in fact alter the result.
And tell us all about the test. Til later. Tom.
Tom Buck ) tel: 905-389-2339
& snailmail: 373 East 43rd St. Hamilton ON L8T 3E1 Canada
(westend Lake Ontario, province of Ontario, Canada).
On Thu, 24 Dec 1998, Earl Brunner wrote:
> ----------------------------Original message----------------------------
> All of this discussion about zinc has got me thinking, I have this glaze that
> really like, It's a very dry matt glaze, from the barium most likely. I reall
> like it's responses and blushes of clor from oxides, especially copper, and i
> gives great effects with some wood ash sprayed lightly over it, in fact, I rea
> don't like the glaze at all unless it has wood ash sprayed over it.
> The glaze is fired to cone 10 in reduction with reduction beginning around 17
> and has 8.8% zinc in it, I think that I had heard/read that zinc volitized, b
> didn't make this glaze formula and just assumed that it must be contributing
> SOMETHING? This is the emperical formula for the glaze:
> Na2O 0.14
> K2O 0.09
> CaO 0.31
> ZnO 0.28
> BaO 0.18
>
> Al2O3 0.41
> SiO2 1.86
>
> It would be anybody's guess what the actual formula would be after the ash is
> sprayed on and combined in the melt. I use unwashed barbecue grill charcoal a
> Since connecting to clayart, I've become more conserned about barium, but most
> my peices are more sculptural and less functional. So generally the barium co
> would not be a problem for me. I'm wondering if I need to reformulate this Gl
> Earl Brunner
>
> Ron Roy wrote:
>
> > ----------------------------Original message----------------------------
> > Thanks to Tom for helping on this - Hamer says ZnO is easily reduced - even
> > slight reduction above 925C will eliminate it from the glaze. To answer the
> > question - will it stay in a reduced cone 6 (1200C) glaze - the answer must
> > be no. Besides this it is not an active flux below 1085C. From this it
> > could be surmised that it is not useful as a glaze flux in reduction at any
> > temperature.
> >
> > It makes sense to me that if it is not reduced until the end of a firing
> > that goes above 1085C that it will help the melt and therefore will have
> > some effect - I also have to assume that if reduced at the end at least
> > some of it will be lost and this will have some effect on the durability
> > and the expansion of the glaze.
>
Assumption Abbey on sat 26 dec 98
At 11:34 12/25/98 EST, you wrote:
>----------------------------Original message----------------------------
>Well, Llewellyn,
>after all this discussion about zinc oxide in a reduction
>glaze, did you ever get any glaze recipes?
>
>Here is a cool glaze that has been around for at least 30 years.
>I've seen it under 2 different names, Porcelain White,
>and Martha's White.
>I think I got Porcelain White in 1972 from my first pottery
>teacher, Clayart's own Tracy Dotson.
>
>This glaze is NOT a balanced glaze. It is actually over-fired
>at cone 10, but that's what makes it fun. It will change from
>a soft off-white semi-gloss (a little cool) to a wild blue/purple
>runny glaze with small white crystals (a little hot). If your
>kiln has a 'hot spot', try it there for some really gaudy effects.
>It WILL run, so use it on the top third of a pot only, or use a
>biscuit on the bottom of the pot, or be sure your kiln shelves
>are protected.
>Don't even mix it up if you are in a school situation where
>others will be using it.
>
>I don't know if the zinc oxide is really doing anything in this
>glaze. I haven't used it in years or done any tests with it. It
>would be an interesting test to mix up a batch with and without
>the zinc.
>
>Porcelain White ^10 reduction
>40 Soda feldspar
>30 flint
>30 whiting
>15 kaolin
>10 zinc oxide
>10 titanium oxide
>
>
>David Hendley
>Maydelle, Texas
>hendley@tyler.net
>http://www.farmpots.com
>--------
Dear David,
thanks for the Titanium/zinc glaze. I think I had one other glaze
submitted and several offered some very good discusions on the role of ZINC
in a glaze. I would like to give your glaze a try. When I do test this
one I will keep your name on file and be sure and get back to you as to my
test results. Right now I have 25 + new glaze tests dry mixed for my next
firing so not sure I will get to this one right now but is a deffinite as I
still want to 'play' with the zinc/titanium theory of glaze colors. Thanks
again for the formula.
Llewellyn Kouba
ABBEY POTTERY
| |
|
