Nancy Udell on mon 13 feb 06
Hello clay buds,
Just moved from the east coast where I had regular access to
Standard, Highwater and Ardvark clays to the southwest where my new
supplier only carries (horrors!) laguna.
Laguan lists all its clays as either cone 10 or cone 5 and then they
have an innocuous statement on the site that says "even though we
list these clays as cone 10 or cone 5, most of our clays have a
fairly broad firing range."
A phone call to laguna to find out what the firing range of the clays
are yeilded no info. They refuse to say and in fact have not tested
the clays except at 10 and 5. The guy at Laguna was very snippy and
rather condescending. Kind of got the feeling: we're laguna, we
don't care we don't have to. And if you're not firing to cone 10
that's your issue, loser...
I know many on this list have more technical expertise with
vitrification and also look down upon clays that claim to fire at
throughout a broad range, cones 6-10 or 7-10, e.g. But that's what
I'm used to (particularly the Aardvark soldate which is marked 6-10).
I have gotten used to what I call the "tissue test." If I can put
water in a vase or cup and leave it on a tissue for two days without
the tissue getting damp, then I know the pot will not ruin tables or
floors.
Has anyone had experience with Laguna clays and firing the cone 10
clays to less than 10 (7 or 8 e.g.)? Has anyone else run into this
issue?
With this move, I'm going back to electric, and really don't want to
fire the electric kiln to cone 10...
Thanks for any input.
Nancy in Santa Fe.
mtigges@NOSPAM.SHAW.CA on mon 13 feb 06
On Mon, Feb 13, 2006 at 11:43:09AM -0700, Nancy Udell wrote:
> With this move, I'm going back to electric, and really don't want to
> fire the electric kiln to cone 10...
I have used Frost, Calico and B-Mix5 at cone 6 - 7.5. B-Mix and
Calico begun to blister at 6.5+, o/w they are fantastic. There is a
canadian clay company which produces a clay very similar to B-Mix,
also marketed as a cone 5 body, however it blisters at cone 6 even
though they say it is ok across 4,5,6.
I hold Lagunas bodies in pretty high regard. Especially Frost. That
stuff is amazing.
Mark.
brendaeverill on mon 13 feb 06
-Hi Nancy,
I will have to check, but a while back some people I know were
getting some really good clay from santa fe. I do think it
was "Santa fe clay", actually, I will have to check on that.
I have used laguna forever. they took over westwood clay and I used
that before laguna even came along.
I am not sure I understood what cone it was you would like to fire
to. I fire to cone 6 bent halfway. oxidation. I would recomend that
you use that range if you want to go lower because there is so much
more clay and glaze recipes that are available for the cone 5-6
range. I do absorbtion tests on all the clays I use. You have to
find one that works for you. I actually use ws4 instead of ws5
because it is more vitrified at 6. all the cone 5 clays that I have
used work fine at 6 except the dark brown,which can bloat if it gets
too hot. The frost porcelain is good, as is the original Hagi. I use
one no one else seems to use, a red clay RSMC.
I know of people who fire the cone ten to only 6, but have not had
any experience of firing them to only 8, but it should be fine. If
it said "our clay will go from cone 6 to cone 10 you would feel
better, but if it didn't test out that way it would not mean much.
I guess everyone gets tired of the "you'll just have to test it, but
it is true."
Brenda in Phoenix
-- In clayart@yahoogroups.com, Nancy Udell wrote:
>
> Hello clay buds,
>
> Just moved from the east coast where I had regular access to
> Standard, Highwater and Ardvark clays to the southwest where my new
> supplier only carries (horrors!) laguna.
>
> Laguan lists all its clays as either cone 10 or cone 5 and then
they
> have an innocuous statement on the site that says "even though we
> list these clays as cone 10 or cone 5, most of our clays have a
> fairly broad firing range."
>
> A phone call to laguna to find out what the firing range of the
clays
> are yeilded no info. They refuse to say and in fact have not
tested
> the clays except at 10 and 5. The guy at Laguna was very snippy
and
> rather condescending. Kind of got the feeling: we're laguna, we
> don't care we don't have to. And if you're not firing to cone 10
> that's your issue, loser...
>
> I know many on this list have more technical expertise with
> vitrification and also look down upon clays that claim to fire at
> throughout a broad range, cones 6-10 or 7-10, e.g. But that's what
> I'm used to (particularly the Aardvark soldate which is marked 6-
10).
>
> I have gotten used to what I call the "tissue test." If I can put
> water in a vase or cup and leave it on a tissue for two days
without
> the tissue getting damp, then I know the pot will not ruin tables
or
> floors.
>
> Has anyone had experience with Laguna clays and firing the cone 10
> clays to less than 10 (7 or 8 e.g.)? Has anyone else run into this
> issue?
>
> With this move, I'm going back to electric, and really don't want
to
> fire the electric kiln to cone 10...
>
> Thanks for any input.
>
> Nancy in Santa Fe.
>
>
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Jon Pacini on tue 14 feb 06
Greetings All ---Hi Nancy
I've always been an advocate of firing whatever clay body at whatever
temperature suits your work. However the vast majority of clays are designed
to be fired at specific temperatures to give specific results. Clays can of
course be fired at any temperature you choose to fire them at. And as a
craftsperson, you need to be aware of the issues involved in firing clays at
various temperatures, particularly at temperatures that the clays weren't
designed to be fired at.
Specifically, you had better be ready for them to vary from the published
specifications.
If it is published that a clay is for a range of temperatures from ^7 -10,
would this mean that the absorbency and shrinkage and warpage all remain the
same for this particular body, no matter if it's fired at ^7 or ^10 ???
That is certainly implied by the stated range of ^7-10. I don't think that
is physically possible, and you as the potter using the clay need to know
that. In spite of what any manufacturer may state about their clays, if you
fire a body to a lower temperature, the porosity rate goes up. And
adversely, as you fire it hotter, it goes down. I think I am on very safe
ground when I say that this is true of pretty much every clay body.
Laguna clays can, in general, be fired at least one cone in either direction
without in most cases running into unacceptable variations. There is no
doubt that some potters fire our clays at even greater deviations from the
designated temperatures. Some potters raku with ^10 porcelain and others
wood fire with ^5 clays. I don't think it is possible however for a clay
supplier to anticipate all the ways a clay may be used and have available
data for every contingency.
Here in the Lab at Laguna we QA all the clays to specific parameters. These
are parameters which fit common conventions or traditions. Tests include
warpage, shrinkage and absorbency at specific temperatures-- ^06, 5 and 10.
Soon I will even have COE charts for the bodies at there designated
temperatures.
But please, don't expect me to have data outside of the parameters that the
clays are commonly used for, clays are used in way too many diverse manners
to have that kind of data available.
If you as a potter have decided to work outside of these common conventions,
that's your call and more power to you. And as I stated above, you are
welcome to fire our clays or any one else's clays at what ever temperature
you wish to, but you will have to do the testing to see whether or not they
will work for you at the temperature of your choosing.
Best snippy, condescending and arrogant regards,
Jon Pacini
Clay Manager
Laguna Clay Co
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