Lili Krakowski on fri 10 oct 08
There is a great deal of confusion about firing temps, etc.
There is no clear demarcation between the levels of firing.
Earthenware can be very low fired, but also fired as high as c.4.
Mid-range generally is considered between c.4 and c.8. Stoneware
runs between c.8 up, BUT a lot of people consider ANY
well-vitrified body stoneware. Porcelain used to be a
translucent totally vitrified white body--very high fired. Today
people speak of c.6 porcelain which certainly is porcellaneous,
but not porcelain--because it is highly fluxed.
Glazes can be made poison free even at very low temps. Plain
soda, plain borax, borax and ash...and the list goes on..
BECAUSE majolica glazes (also faience and earthenware) generally
were made of lead, as were (obviously) galena glazes, there is a
general assumption that lowfired glazes necessarily contain
poisons.,
I need to add that even much higher fired glazes contained
lead--Leach, for instance, added red lead to stoneware glazes to
get the melt going.
But there is another line of demarcation to consider.
Absorption. Permeability. One can fire relatively low and get a
well vitrified body. One can fire quite high and keep a lot of
porosity. Again: there is no clear line of demarcation.
I think a lot of people look down on earthenware because it
generally is "folk art", more likely to be sold at farm markets,
feiras etc, than in fancy shmancy galleries. Also a lot people
look down on earthenware because high fired ware is costlier, and
in the recent "art" climate has a better renomme. As do French
wines for instance in relation to Australian or Chilean
etc.--which are excellent.
Please do not assume that if it is earthenware it is not foodsafe
and if it is stoneware or "porcelain" it is.
Lili Krakowski
Be of good courage
Taylor Hendrix on fri 10 oct 08
And do not think that just because the wine was made in Texas that it
doesn't taste good either. When they start putting it in a box, I'm
really going to be happy.
Paul McCoy at Baylor University fires his studio earthenware up to mid
fire with glazes. I've got one of his bowls. It feels and sounds like
mid fired stoneware. Nice red body too. It holds the ice cream no
matter what you call it. Yummy.
Hey Mama, do you still use that little bowl I sent you? I bet I've
improved a little.
Tay Tay, in Rock Rock
On Fri, Oct 10, 2008 at 11:13 AM, Lili Krakowski
wrote:
> There is a great deal of confusion about firing temps, etc.
>
> There is no clear demarcation between the levels of firing.
> Earthenware can be very low fired, but also fired as high as c.4.
...
> But there is another line of demarcation to consider.
> Absorption. Permeability. One can fire relatively low and get a
> well vitrified body. One can fire quite high and keep a lot of
> porosity. Again: there is no clear line of demarcation.
...
Also a lot people
> look down on earthenware because high fired ware is costlier, and
> in the recent "art" climate has a better renomme. As do French
> wines for instance in relation to Australian or Chilean
> etc.--which are excellent.
...
Jeanie Silver on fri 10 oct 08
Thankyou Lilly, for your knowledgeable explanation of some of the reasons
why earthenware has been marginalized in modern studio practice. No
particular claybody or process is, by definition, better than another...it
is possible to make earthenware that functions well for its intended
purpose, with stable glazes, formulated for proper fit, from ingredients no
more toxic than those for higher temperatures. I know- along with some
other American, English, and French potters, I have been doing just that for
quite a few years...its also possible, to make weepy stoneware with badly
fitting, leaching glazes, poor forms, indifferent surfaces and no real
reason to exist....
Properly fired stoneware will always have the advantage of greater chip
resistance over earthenware...
Properly crafted terracotta has the advantage of little clay memory and
greater green strength,,,and there are those who get a creative bounce from
its exuberant color and long association with the work of indigenous peoples
and children. I think that's pretty nice company to keep...
Jeanie in Pa.
Paulette Carr on sat 11 oct 08
Thank you Lili for addressing the confusion regarding low-fire
work. ... and to Jeanie for adding to the discussion! As I
mentioned before, low-fire work comes in many flavors - not just red
terracotta, and majolica. Not all earthenware clays are red... and
not this all work is intended to be functional for the table-top...
sometimes, architecturally functional. I believe that those who
seriously choose to work at this temperature become knowledgeable
about the technical aspects of their clay and glazes - as much as
those who choose to work at higher temperatures. And if you are
interested, you will find glazes that are as complex and beautiful -
and safe - as the glazes used for mid- and high-fire work.
Paulette Carr
Paulette Carr
St. Louis, MO
Member Potters Council
Jeanie Silver wrote:
Properly crafted terracotta has the advantage of little clay memory and
greater green strength,,,and there are those who get a creative
bounce from
its exuberant color and long association with the work of indigenous
peoples
and children. I think that's pretty nice company to keep...
Jeanie in Pa.
Paulette Carr wrote:
Kelly,
Perhaps I am a little prickly, but when someone mentions low-fire
work in a dismissive manner, I feel obligated to open the window of
education just a crack. Though the word "dilettante" is mine, you
did specifically say, "that potters like you [Mel] who don't buy
their glazes in little jars, and don't fire at low temps, can MAKE a
glaze out of clays and feldspars and non-toxic mined materials.". I
am not personally feeling slighted/injured or argumentative, just
opening that information window... and making an effort to correct
your impression. Like all clay work, low-fire work comes in many
flavors, not just the painterly majolica of Ann Tubbs, Linda
Arbuckle, and others... why there are even some crystalline glazes in
this temperature range in the forms of adventurines. I am in the
middle of glazing a 7' x 8' mosaic mural, built from a low-fire talc
clay body, and made with glazes developed from the materials that I
mentioned in my earlier communication - nepheline syenite, gillespie
borate, Frit 3134, flint, EPK, OM4 ball clay, bentonite, and
macaloids, Fe2O3 and mason stains... no lead, no "bad juju".
Your information regarding the making of low-fire glazes is a little
dated: To the best of my knowledge, there are very, very few
contempory potters/ceramic artists that use lead any more (and have
not for many years!). Apparently, a non-leaded glaze is not the same
as a lead glaze in terms of flow and surface, but I never used Pb -
never would, and do not know what I am missing... which in my opinion
is not much. Many potters use manganese, barium, cadmium,
radioactives (lanthanides and actinides), copper, chromium, cobalt.
They fire at many temperatures, so these potentially dangerous heavy
metals are not limited to the low-fire potters to whom you alluded.
IMO, if you undertake to use these materials, then you must be aware
of the hazards in handling, use them safely (for yourself and
others,), dispose of them properly, and finally, place them on
surfaces that are not fugitive in use. I think that if you checked
the current issue of manufactured glazes, you would find few made
with lead, and if they are, it must be on the label. As you know,
what you usually receive in the form of donated materials are
materials that have not been readily available or used for years.
Hopefully, all teachers will be required to read labels and ask
questions before allowing their students to use potentially dangerous
materials - or have the good common sense to be concerned.
One can make a perfectly safe and stable glaze that fits a given clay
body at any temperature - EVEN at low-fire temperatures. If it were
possible to check the Clayart archives, you would find many entries
for low-fire glaze recipes sans the objectionable materials. A quick
check of more recent literature will net you many "safe" glaze
recipes... and then you must make them work for your clay body at
your temperature, and the way in which you work and fire.
If you are drinking from anyone's mugs, or eating off of their
dishes, I would hope that you would be as concerned about whether and
how they make their glazes, as you are - and rightly should be! -
with their modus operandi for disposal. Enjoy your coffee in your
amazing mug! I am eager to hear of the progress on your commission.
My best,
Paulette Carr
Paulette Carr Studio
St. Louis, MO
Member Potters Council
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