John Rodgers on fri 11 jun 04
Shopping for info on clay body characteristics for jiggering.
My experience in a production environment one time in the past was
limited to the clay that was ordered in. I had no technical specs on the
clay. I just remember it was far softer than the standard pug. I have
seen film of jiggering production in a plant in Kentucky and there the
clay was pumped through a hose right to the point of squirting under
pressure into the jigger mold. So I know jigger clay needs to be quite
soft. More so than the standard pug.
Has anyone any information on what a proper clay/water ratio is for this
purpose? Any chemicals added to soften the clay? I maybe would like to
mix my own, or perhaps work up some reclaim with the right consistency.
I would also like to know of any sources - clay companies in the
southeast that produce such clays.
Any input is appreciated.
Thanks.
John Rodgers
Chelsea, AL
WHC228@AOL.COM on sat 12 jun 04
John
I am no longer jiggering, but I would be happy to discuss Jiggering with you.
I did it for a long time and could share some of what I know.
The plant in KY that you are talking about is Louisville stoneware. I was
there years ago to take a tour of their plant. They use their clay like slip. The
slip is poured into the mold, and allowed to be there long enough to start to
work like a slip mold. The excess is poured away, and more clay is
introduced. This clay is very wet. Just out of the diaper soft. It is then shaped with
the profile tool while spinning.
The clay that they use is delivered in dump trucks and piled outdoors in a
huge pile. From what little I could see, it appeared that the clay really wasn't
very user friendly.
Someone I met recently mentioned that they were trying to sell their press
because they were having quality problems with it. It sounded like a clay
related problem. They were also having problems with their casting operation when I
was there. That was definitely a clay problem.
A good clay body and an understanding of how to manipulate its plasticity up
and down a deflocculation curve can be very helpful when trying to Jigger,
slipcast, or press.
It appeared that Louisville Stoneware didn't understand that, of their
insistence on using only one local clay forced them to have to use the jiggering
method that I described.
Hall China in East Liverpool, Ohio uses a more traditional method of
jiggering. It is a three man team. The first man on the team is called the "batter
out." His job is to get a bit of soft clay, and put it down onto the surface of
the Batt machine. That part of the machine is lifted up so that the clay
interferes with some spinning trowels, that look like fan blades.
This fattens the clay and smoothes it into a soft slab. The clay is lifted
off the machine and is laid onto the top of a jigger mold and a slit is made
through the clay so that the air that is under the clay can get out when the
jiggerman does his job.
The next man to handle the clay is the Jiggerman. He picks up the mold, and
places it into a spinning chuck. He takes a very wet sponge, and pushes the
clay down into the spinning mold and runs it up and down to force the clay to
conform to the shape of the mold. When he is finishing he forces enough of the
clay down into the center of the pot to form a nipple.
The nipple is an inch or so high and as big around as a half dollar.
At that point he then brings the profile tool in contact with the clay and
the final shape is made. He briefly trims the rim of the pot with a wooden tool
and picks up the spinning mold and hands it to the next man.
The next man is called the Mold Runner.
This man places the mold into a drier that they call a Stove Box. while he is
at the drier shelf he removes the mold that has been dried. He removes the
leather hard piece and cleans up the edge of the rim, and gives the empty mold
to the Batter Out.
Using that three man team a factory can produce a lot of fairly high quality
shapes.
Studio potters usually don't work as a team that way, and wouldn't be able to
use the volume of pots that can come off a jigger. They usually use a clay
that is more like soft throwing clay.
If you want to discuss how we did it in our studio let me know.
You may not get an instant answer, but I will answer. Send me a phone number
and I will be happy to share whatever I know about Jiggering.
Bill Campbell
Des & Jan Howard on mon 14 jun 04
John
We break up clay soft/firm into 3 consistencies:
- Jiggering - Clay is soft, nearly sticky, but not sticky - most shapes have quite deep foot rings.
- Throwing - Soft, leaves a smear on the wedging table, but does not stick.
- Extrusion - Hollow shapes, firm - handles, firmer.
Clay can be hand wedged in both cases without too much difficulty.
Clay water content is controlled by:
- Porcellaneous stoneware - length of cycle on the filter press - 8 hours for jiggering clay,
9 hours for throwing clay & 10 hours for extruding clay.
- White porcellaneous stoneware & "grit" bodies - amount of carefully measured
water added to batch in dough mixer.
Des
John Rodgers wrote:
> Shopping for info on clay body characteristics for jiggering.
>
> My experience in a production environment one time in the past was
> limited to the clay that was ordered in. I had no technical specs on the
> clay. I just remember it was far softer than the standard pug. I have
> seen film of jiggering production in a plant in Kentucky and there the
> clay was pumped through a hose right to the point of squirting under
> pressure into the jigger mold. So I know jigger clay needs to be quite
> soft. More so than the standard pug.
>
> Has anyone any information on what a proper clay/water ratio is for this
> purpose? Any chemicals added to soften the clay? I maybe would like to
> mix my own, or perhaps work up some reclaim with the right consistency.
--
Des & Jan Howard
Lue Pottery
LUE NSW 2850
Australia
Ph/Fax 02 6373 6419
http://www.luepottery.hwy.com.au
| |
|
