Linda Arbuckle on thu 4 jun 98
Norm,
I would be careful using neph sy as the body flux. It can be partially
soluble and deflocculate the clay body. Make the clay particles line up
parallel and slightly repel each other. Clay is hard to work with. Feels
too wet, then dries on the outside, particles sit together, and inside
water has trouble wicking out. Can cause cracking. We tried a recipe w/a
lot of neph sy this spring, and it was just penance to work.
Pete Pinnell gave us this advice:
I don't know a distinct recipe, just some general guidelines. For a
cone 6 light body you need about 20-25% flux with the rest being clay
or a clay/filler combination. Neph sy can work but it will tend to
deflocculate the clay unless it is counteracted with either epsom salts
or calcium chloride. Soda spar or G-200 will also work, but are not as
active so the clay will tend to be a bit more porous. You can also add
just a small amount of talc and that will really tighten up the clay,
but at a slightly heightened risk of cristobalite. The strongest
spar/talc eutectic is at a ratio of five or six parts spar to one part
talc.
As for clay, it can be "to taste". It will stand up a lot better and
crack a lot less if there is some fireclay, though very much will push
the color to buff. Similarly, a little ball clay goes a long way to
promote plasticity. Kaolin will give the whiteness, but you can't use
it alone unless you also add some other filler such as flint or
pyrophyllite. If it were me i would start with the following:
Fireclay 20, ball clay 20, tile #6 kaolin 25, flint 10, kona f-4 spar
25, bentonite 1. This will be pretty off-white (cream to buff), so if
they want whiter they will have to accept the lower workability of a
high kaolin body. They may want to add grog, in which case you could
use something like Ione Grain if they want whiteness without the cost
of Molochite. Kona can also cause deflocculation, so a little
flocculant (one quarter percent) might be a good idea. Have them
dissolve it first in hot water.
This is just a starting point- they can adjust any of the components to
fit their needs.
--
Linda Arbuckle
Graduate Coordinator, Assoc. Prof.
Univ of FL
School of Art and Art History
P.O. Box 115801, Gainesville, FL 32611-5801
(352) 392-0201 x 219
e-mail: arbuck@ufl.edu
Mike Gordon on fri 30 dec 05
Randy,
I use Laguna's Soldate 60 clay at Cone 6-7 all the time, with no
problems. I throw shot glass size's to the full bag with this clay. No
cracking. Mike Gordon
Mike Gordon on fri 30 dec 05
Randy,
I use Laguna's Soldate 60 clay at Cone 6-7 all the time, with no
problems. I throw shot glass size's to the full bag with this clay. No
cracking. Mike Gordon
Teresa Griffin on wed 4 jan 06
I use Laguna's Soldate 60 clay at Cone 6-7 to throw display pieces. I do
not have any problem with cracking.
I like it because it is soooooo easy to work with and it is light weight.
Chaeli Sullivan on wed 24 oct 07
Hello folks
Until now i've been firing stoneware cone 6 clay to cone 6. However,
would like to try out a new Cone 8 glaze and i wondered if i can fire the
clay to Cone 8. Will it survive? Or like earthenware clays melt at the
higher temperature?
Thanks
Chae
Roseanne Breuer on wed 24 oct 07
Contact the manufacturer for the details on your clay firing temperature.
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Nancy on wed 24 oct 07
I think it depends on the clay. I have overfired my cone 6 Laguna clay
(bmix, bmix with grog and #66 as well as standards 206 and the old 245)
and it's been okay. There are ranges for the clay bodies. I'd check
with your supplier for your particular brand of clay.
Nancy
www.hilltoppottery.com
Chaeli Sullivan wrote:
> Hello folks
> Until now i've been firing stoneware cone 6 clay to cone 6. However,
> would like to try out a new Cone 8 glaze and i wondered if i can fire the
> clay to Cone 8. Will it survive? Or like earthenware clays melt at the
> higher temperature?
> Thanks
> Chae
>
> ______________________________________________________________________________
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>
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>
Chaeli Sullivan on thu 25 oct 07
Thanks for the suggestions to call the manufacturer. Did that today and
Seattle Pottery said that their Cone 6 clay can actually fire at Cone 5
but would more than likely have disastrous effects at Cone 8.
So perhaps it's a happy happenstance that the new kiln stalled out at 1900
degrees!
Chae
Ron Roy on fri 28 aug 09
There is no magic involved in making a cone 6 body - mix up some clay,
melter, and silica and test - if it needs more melter - add more - if less
melter is needed leave some out. I'm making it sound simple and we all know
there is more to it than that - but we learn as we go along.
I have done this now for a number of potters - get the body right then get
your local clay maker to mix it for you. I never took more than a few hours
of my time and usually got the required result in 2 or 3 tries.
I have an advantage because I can compare (using calculation) to the clays =
I
monitor for Tuckers up here in Ontario. I have years of test data on raw
clays and bodies formulated to fire at specific temperatures. It has become
easy for me to make clay bodes that work.
All that aside - if you are thinking of making you own clay - I can help -
turning something that could go on for years into something that will work
in months or weeks.
All I need is a list of the clays your clay maker stocks, what colour you
want the clay to be and what cone (cone 6 and over) you want it to be leak
proof at. Can't do it with low fire clay - sorry!
RR
On Tue, Aug 25, 2009 at 9:21 PM, Ingeborg Foco wro=
te:
> Dave,
>
> First of all how nice to hear from you. How are you? It's been a while.
>
> Do I need to get a clay body ^6 , probably not but I frequently think
> about
> it when all of these discussions come up. I think it is a great way to
> fire
> if you can figure out the details and I tend get caught up in the
> conversation and think I maybe should be more green if you will.
>
> Ron Roy gave me great information on how to test my clay body when I fir=
st
> came to Florida shopping for clay. He told me how to test for for warpag=
e,
> absorption and shrinkage. I would definitely agree with Michael on the
> differences in a kiln and how it fires in different areas. I place cone
> packs all over the kiln and am always amazed at the differences. With th=
e
> rising costs of cones I always want to cut back on cone packs but
> ultimately, it is the way to figure out what is going on inside because t=
he
> three peeps up front just don't give you the whole picture.
>
> I just find the lower firings intriguing and feel as though I should
> investigate so as not to be left behind in the dust so to speak. My
> customers like the variety of glazes and the types of glazes I have so I
> have to be very careful if I change things. What will they think and wil=
l
> they buy the new work, that is the ultimate question.
>
>
> --
> Sincerely,
>
> Ingeborg
>
> http://www.thepottersworkshop.com
>
> ug 25, 2009 at 4:54 PM, Dave Finkelnburg wrote:
>
> > Ingeborg,
> > Do you get the idea you need a cone 6 clay body? :-) While that
> > advice has been echoed by many, Snail's comments also shed light on the
> > subject. Back in the 20th century I found Clayart because I had a "Con=
e
> 5"
> > clay that didn't mature at that cone. Many on the list then advised I
> > needed to fire that clay to cone 6 and sure enough, that solved my
> problem
> > of leaking pots.
> > With that in mind, here's some of what happens at cone 6. First,
> glass
> > forms in the clay body and clay begins to convert to mullite. At NCECA
> in
> > Kansas City, Dr. W. Carty showed video of rods sagging in a furnace at =
a
> > temperature well below maturity because glass formation was letting the
> > slumping occur. He hypothesized that poor ingredient mixing was letting
> > pockets of glass form in the body and permit the slumping. Research by
> his
> > group has confirmed that hypothesis and demonstrated that the ratio of
> > silica to alumina in the clay body glass phase is constant. Excess
> silica
> > above that needed to make the glass phase just comes through the firing
> as
> > inert (silica) sand filler. Too much of this particular filler is a
> problem
> > during cooling through the quartz inversion but virtually all porcelain=
s
> > have at least some excess silica to guarantee sufficient glass phase to
> > yield a strong, dense clay body.
> > As you know, to test any new body in your kiln, make test tiles of
> > known dimensions and measure the shrinkage beside witness cones and at
> > recorded temperatures. Then check the tile for absorption. I recall R=
on
> > Roy advising me a decade or so ago to shoot for less than 3% absorption
> in
> > stoneware, less than 1/2% (preferably ~1/4%) for porcelain.
> > As Michael Wendt has demonstrated so clearly this month, a pot in t=
he
> > middle of the kiln may not see the same temperature as a pot near burne=
rs
> or
> > elements so knowing what temperature and time or cone position fires th=
e
> > entire load will save a lot of headaches.
> > Good potting!
> > Dave Finkelnburg
> > http://www.mattanddavesclays.com
> >
> > __________________________________________________
> > Do You Yahoo!?
> > Tired of spam? Yahoo! Mail has the best spam protection around
> > http://mail.yahoo.com
> >
>
--
Ron Roy
15084 Little Lake Road
Brighton, Ontario, Canada
K0K 1H0
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