Lili Krakowski on tue 21 dec 04
Someone is in need of a Basic GLaze Book. like Fraser's
SLIP glazes essentially are "special" clays with fluxes added to make =
them into glazes. They are MOSTLY clay.
Calcium chloride and Epsom Salts are FLOCCULANTS, What they do, to be =
simple, is that they turn the glaze particles from grits to popcorn. =
(Experts, please! If you can deal with teapot scrotums (yikes) and =
virgins on their wedding night (YIKES) you can deal with popcorn!) =
Having said this, it makes the glaze ever so much nicer to use, and it =
does not settle like rock at the bottom of the bucket.
Why Borax? Dear heart! Borax is Na2O, 2B2O3,10H20 and Epsom salts are =
Magnesium sulphate!
If you need to buy; Epsom salts come in various ways. Farm supply =
houses: cheap. Drug stores: for bath use cheaper than for internal =
use. Calcium chloride is used for melting ice, so it is availabe at =
farm tire places, and at hardware stores...but in big quantities. A =
farm tire place will give you some. It is very corrosive on metal, so =
keep in plastic jar.
As to African violets. I do not get the picture, and AV's drop dead at =
sight of me. Have you considered of making the clay for the insert more =
refractory? =20
Lili Krakowski
Be of good courage
Kate Johnson on tue 21 dec 04
Hi Lili, Ivor, Tig, Charles, and all who have responded to my question about
dry ash glaze, on and offlist--I'm glad I asked again. Interestingly, I had
only found it mentioned in that one book by Birk (cryptic at best, there)
and nowhere else, but figured someone here would have had personal
experience.
> Someone is in need of a Basic GLaze Book. like Fraser's
I expect that "someone" would be me, among others! Is that the name of
Fraser's book? Are there others that Clayart members especially recommend?
I already own Ron and John's wonderful book on ^6 glazes (unfortunately on
loan to a friend at the moment), and many other books with glaze chapters or
recipes, but had not found mention of dry ash in any but the one, hence my
question about whether anyone here had tried it. There's been a great deal
of discussion about ash glazes, but all involved mixing or sprinkling into
wet glaze...none, as far as I could find, talked about dry ash by itself,
onto a wet bisque pot.
I know there are basic principles and information, such as the chemical
makeup or components of each ingredient, and that should be in any glaze
book, but what I am interested in, mostly, at this point in my quest (as
Ivor suggested, I AM focusing), are *lowfire* glazes to fit my red
earthenware/Colonial or English slip-decorated work, with side forays into
more primitive stuff. When I master that...IF and when...I'll move on to
other areas, I'm sure.
What I was wondering was if the dry ash glaze would flux at the temperatures
I use...awfully simplistic question I know, but I always assume that there
are others on this board who have an interest in the basics, too--or the
early ways, the simplest ways. I hope that there are other amateurs here
who benefit from my questions, just as I do from someone else's.
Dry ash glaze seems as though it would be something very primitive indeed,
but probably not an option at my firing temps. Thank you to all who
responded--to a man (and woman) the consensus seems to be ^6 and higher.
> SLIP glazes essentially are "special" clays with fluxes added to make them
> into glazes. They are MOSTLY clay.
Thank you...
> Calcium chloride and Epsom Salts are FLOCCULANTS, What they do, to be
> simple, is that they turn the glaze particles from grits to popcorn.
> (Experts, please! If you can deal with teapot scrotums (yikes) and
> virgins on their wedding night (YIKES) you can deal with popcorn!) Having
> said this, it makes the glaze ever so much nicer to use, and it does not
> settle like rock at the bottom of the bucket.
Nice image, thank you! (How did I miss the virgins....) I understand
what flocculants do, but I love the way you've used the analogy. My
flocculant image is similar to the way that oil, vinegar, and egg yolk in
proper suspension become mayonnaise.
>Why Borax? Dear heart! Borax is Na2O, 2B2O3,10H20 and Epsom salts are
>Magnesium sulphate!
Ooops. Must dig out my basic chemistry book before asking. Or what the
heck, ask and assume others will benefit, too.
Ivor wrote:
There are so many variable factors from which to choose. Type and
constitution of clay? Origin of the Ash/? Processed or unprocessed Ash
? Which cone to choose? Oxidising, neutral or reducing fires.
Indeed! And of course I didn't make clear that I was asking in context of
what it is that I am focusing on--lowfire earthenware in an attempt to
explore the pottery of the past. Mea culpa! And many thanks, again, for
all your help--Clayart's an amazing place. I don't always find what I'm
looking for in the archives, for one reason or another, but the generous
souls here offer information wondrously freely, as someone said yesterday.
Many, many thanks. I am finding the challenge of experimenting exciting and
invigorating, and as Tig suggested, keeping records of what I've done to
provide guidance. Occasionally it's nice to hear the voice of experience,
here, too, of course...
Regards,
Kate Johnson
Graphics/Fine Arts
http://www.cathyjohnson.info/
http://www.epsi.net/graphic/
http://www.ebsqart.com/Artists/cmd_1494_profile.htm
Ivor and Olive Lewis on wed 22 dec 04
Dear Kate Johnson,
Book ref is Harry Fraser, "Glazes for the Craft Potter". First
published 1973. New edition 1998, ISBN 90-5703-01-28. A & C Black.
Says very little about Ash Glazes. Nor would other information in the
book give you the intellectual tools to reason out what might be
expected to happen in the situation you describe.
The temperature at which any ash will commence to melt will depend
upon its true chemical composition, not on the abstract elemental
oxide interpretation of your original ash mixture. We can make an
assumption that raw ash will contain both Potassium and Magnesium
compounds, and some form of Phosphate because these are elements
essential to the life of all plants. Calcium also feature in the
analyses of most ashes
During firing, Potassium and Magnesium may be converted to Carbonates
and the Phosphorus could become a Tri-Calcium Phosphate. Potassium
Carbonate has a relatively low melting point in comparison to your
firing temperature but is soluble and most of it will be removed if
your ash is washed. Tri-Calcium Phosphate Melts at a much higher
temperature than your chosen maturing temperature range and Magnesium
Carbonate decomposes to give Magnesium Oxide which is highly
refractory.
I would anticipate obtaining good results with an unwashed ash since
Potassium carbonate will melt and promote both the formation of a bond
with the clay and an environment in which other materials can
dissolve. If this fluid is a good solvent of both clay and free silica
what occur in our clay then you may get excellent results provided you
can (a) maintain your top temperature for a prolonged period of time
and (b) go to the top of your chose firing range.
I foresee only one problem with the method you describe. Sifting dry
ash onto a pot which has a wet surface may cause the dissolution of
some of the soluble materials and these could be drawn into the drying
clay be capillary action, reducing melting potential of your ash at
the surface. This might be countered by allowing the clay to dry, or
even bisquing, then spraying twice with a strong adhesive before
sifting the ash onto the shoulders of your pots, the first time to
seal the clay and when that has dried, a second time to adhere the ash
in place.
I look forward to learning of your results and wish you every success
with your work.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
Kate Johnson on wed 22 dec 04
Hello Ivor, and thank you...
> Book ref is Harry Fraser, "Glazes for the Craft Potter". First
> published 1973. New edition 1998, ISBN 90-5703-01-28. A & C Black.
> Says very little about Ash Glazes. Nor would other information in the
> book give you the intellectual tools to reason out what might be
> expected to happen in the situation you describe.
Ah. Well, I am glad to hear you believe it might be feasible for my firing
temps--I was just going to set the idea aside until I got back to stoneware.
I was forseeing rather a lot of experimenting, but not till then.
What I find frustrating about glaze books or pottery books containing glaze
recipes of that age, of course, is that the safety concerns just weren't
what they are today. Rather a lot of information I won't be using...
Thank you for the above excellent (snipped) information, I will file it in
my "answers" folder.
> I would anticipate obtaining good results with an unwashed ash since
> Potassium carbonate will melt and promote both the formation of a bond
> with the clay and an environment in which other materials can
> dissolve. If this fluid is a good solvent of both clay and free silica
> what occur in our clay then you may get excellent results provided you
> can (a) maintain your top temperature for a prolonged period of time
> and (b) go to the top of your chose firing range.
I believe I can do that, and will also keep these suggestions at hand.
> I foresee only one problem with the method you describe. Sifting dry
> ash onto a pot which has a wet surface may cause the dissolution of
> some of the soluble materials and these could be drawn into the drying
> clay be capillary action, reducing melting potential of your ash at
> the surface. This might be countered by allowing the clay to dry, or
> even bisquing, then spraying twice with a strong adhesive before
> sifting the ash onto the shoulders of your pots, the first time to
> seal the clay and when that has dried, a second time to adhere the ash
> in place.
I had planned to bisque fire, first, so that should alleviate some of the
tendency toward dissolution and absorption by capillary action. Still,
bisque being somewhat porous (particularly if it's earthenware, which is
what I will be using), if I wet it I may still get some dissolution. We'll
see!
But I'm intrigued by your suggestion of using an adhesive. What have you
used on bisqueware? I'm aware that some glues can be used and simply burn
off when fired, but I'd be hesitant just to get out the Elmer's Glue-all!
> I look forward to learning of your results and wish you every success
> with your work.
Many thanks...it is quite an adventure!
By the way, enjoyed the new CM with some really lovely ash-glazed pots by
Makoto Yabe, fired in an electric kiln. I hadn't expected to be able to get
results like that with an electric, though I know John and Ron certainly
have gotten glorious results! I'm anxious to try some of these ideas and
techniques.
Best--
Kate
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