Wood Jeanne on sat 14 apr 01
Hi,
I'm having a problem with handles cracking. They crack
across their middle after they have been attached to
the pot and dried to leather hard stage. Although I've
gone to great lengths to insure they dry evenly and
slowly (plastic, newspaper, dampbox).
I've always kept a separate stash of handle pulling
clay separate from my throwing body. It consists
mostly of my throwing body but more aged & sometimes
with a little commercial clay thrown in, no exact
measurements, and in the past it's done quite well.
The cracking began when I changed my claybody a little
to the following:
parts by volume
Helmer Kaolin 4 parts
Custer Feldspar 2
ball clay 1
fine mesh silica sand .5 or (1/2)
This recipe hasn't been plastic enough for my style of
handles and my old handle pulling clay cracks, as I
wrote above.
Any ideas?
Thanks in advance.
Jeanne W.
In Northern Idaho where it hasn't snowed yet today,
first day in a couple of weeks.
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Stephen Grimmer on sun 15 apr 01
Jeanne,
First, I'd convert that clay recipe to weight rather than volume. Dry
clay powder can not be accurately be measured by volume. If you mix by
volume, you don't really know what's in there. Second, I'd add 2% bentonite
by weight to the body. The bentonite will plasticize the clay and make it
stronger without appreciably increasing shrinkage. Mix your new clay body
and age for a month or so; it should be fine for handles now.
Do you pull handles right off your cups? I'd recommend doing that when
the cup is still a bit soft. Start with a slug of clay that is nearly the
size and shape of the handle you want. The more you pull the clay out, the
worse cracking is. Then try this: dry a completed cup quickly, in the open
air. Don't cover it with anything. It seems that when pulled handles are
kept wet for a long time, they crack a lot more.
Good luck,
Steve
--
Stephen Grimmer
Southern Illinois University at Carbondale
> From: Wood Jeanne
> Subject: bad handle on that mug
>
> Hi,
> I'm having a problem with handles cracking. They crack
> across their middle after they have been attached to
> the pot and dried to leather hard stage. Although I've
> gone to great lengths to insure they dry evenly and
> slowly (plastic, newspaper, dampbox).
>
> I've always kept a separate stash of handle pulling
> clay separate from my throwing body. It consists
> mostly of my throwing body but more aged & sometimes
> with a little commercial clay thrown in, no exact
> measurements, and in the past it's done quite well.
>
> The cracking began when I changed my claybody a little
> to the following:
> parts by volume
> Helmer Kaolin 4 parts
> Custer Feldspar 2
> ball clay 1
> fine mesh silica sand .5 or (1/2)
>
> This recipe hasn't been plastic enough for my style of
> handles and my old handle pulling clay cracks, as I
> wrote above.
> Any ideas?
> Thanks in advance.
> Jeanne W.
> In Northern Idaho where it hasn't snowed yet today,
> first day in a couple of weeks.
Lorraine Pierce on sun 15 apr 01
Hi Jeanne...sounds to me as tho the two clays are not compatable. Try making
a mug and handle of the clay you now use for the handles only, and observe
what happens. Good luck. Lori in New Port Richey, Fl.
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