Steve Slatin on wed 3 aug 05
Mary --
There isn't any special correlation between clay
maturing temperature and strength when moist.
Some clays do collapse earlier than others. Some are
softer than others. But the combination of collapse,
softness, and pastiness points to the clay being too
moist for the way you're working it. (Folks work
their clay differently; the manufacturers seem to aim
for the middle but batches do vary and maybe you got
some clay designed for different handling.)
When I have this happen, I flatten it down to maybe 2
or 2 1/2 inches on a plaster bat and let it dry for a
good spell -- 2-5 hours if it's dry & warm outside,
and overnight if it's moist and/or cold -- wedge it up
and try again.
I've never found a clay that was throwable (I'm
talking throwable with a powered wheel, using moisture
on the fingers) if it was at all tacky when I was done
wedging it. It doesn't take a lot of moisture to get
a clay from nice to too wet to throw (maybe a half cup
for a 25-lb bag?)
Best wishes -- Steve Slatin
--- Mary/Adams wrote:
> I have so far been using Cone 10 clays (various
> ones) and now want to work
> with Cone 5 and 6 clays. I have been trying that
> out and they seem to be
> pastier and softer and collapse easier. Is this
> typical? The cone 5 and 6
> clays are (Laguna Dover cone 5 and Laguna EM22 cone
> 6). Any suggestions?
Steve Slatin --
Drove downtown in the rain
9:30 on a Tuesday night
Just to check out the
Late night record shop
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Mary/Adams on wed 3 aug 05
I have so far been using Cone 10 clays (various ones) and now want to work
with Cone 5 and 6 clays. I have been trying that out and they seem to be
pastier and softer and collapse easier. Is this typical? The cone 5 and 6
clays are (Laguna Dover cone 5 and Laguna EM22 cone 6). Any suggestions?
Mary
Snail Scott on thu 4 aug 05
At 04:45 PM 8/3/2005 -0700, you wrote:
>I have so far been using Cone 10 clays (various ones) and now want to work
>with Cone 5 and 6 clays. I have been trying that out and they seem to be
>pastier and softer and collapse easier. Is this typical?
No. I doubt that you are perceiving any difference
between temperatures. It's just that the few mid-
range clays you've used so far happen to be more
plastic than the ^10 clays you've used in the past.
A question to determine: Are these clays too plastic
because they are overly damp, or because the recipe
contains more plastic materials? If you aren't sure,
wedge some until it's a bit drier, and try again.
If it was just too damp, that should cure it. If it
was simply too plastic for your taste, it'll just get
more difficult to throw.
If it's just too damp:
Even well-sealed clay will dry out eventually, so
some clay companies try to ship on the wet side of
optimum, so that it'll still be usable when you get
to the last of the batch you bought. That does mean
that the really fresh stuff can be a bit too damp,
but that's easier to cure than being too dry. Wedge
a little longer, or when you make up the balls of
clay before you throw, let them sit longer before
using them. Making them up a day early (but keeping
them covered) might do the trick. By the time you
finish the shipment, it may not be necessary any
more.
If it's just too plastic:
I won't recommend any specific clay, since I seldom
work with throwing bodies, but don't give up. Try
other clays. Lagua has a chart in their catalog with
the properties of their various clays, including
shrinkage. As a rule of thumb, high-shrinkage clays
are also the most plastic, so if you find a few clay
bodies with the properties you're seeking (color,
temperature, or whatever), check their shrinkage
numbers and compare them with the Laguna bodies
you're presently unhappy with, and go for a lower
percentage.
-Snail
Ron Roy on sat 6 aug 05
Hi Mary,
It is a little harder to get good workability with cone 6 clays - you need
to add more melter to get a vitrius body at the lower temperature.
I can be done but you may have to shop around a bit to get what you want.
Just remember - if you are making functional ware - to make sure it does
not leak at the temperature you fire it to.
RR
>I have so far been using Cone 10 clays (various ones) and now want to work
>with Cone 5 and 6 clays. I have been trying that out and they seem to be
>pastier and softer and collapse easier. Is this typical? The cone 5 and 6
>clays are (Laguna Dover cone 5 and Laguna EM22 cone 6). Any suggestions?
>
>Mary
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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