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warping plates: for anne

updated sat 17 nov 01

 

Cindy Strnad on sat 10 nov 01


Dear Anne,

I'm thinking of "Anne--with an 'e' ". (My daughter
loves Anne of Green Gables, in case that reference
doesn't mean anything to you.) I've never trimmed
foot rings on my plates because . . . well,
because I just don't do it. Unless I want a
pedestal, anyway. But I'm surprised you end up
with spinners even though you do trim a foot ring.
And I'm wondering why you don't fire to
vitrification? Are you working in low-fire?

First, the vitrification: If you want your glazed
plates to be dishwasher and microwave safe, you
need to fire them to vitrification. Unglazed ware
is a different matter, but with glazed ware, when
washing (even hand washing), the clay body will
soak up liquid which can cause damage in the
microwave oven when the water vaporizes. Maybe in
a conventional oven, too. Even if you never put
them in any kind of oven, the bases can (and
will--yes, I've experienced this though I live in
a semi-arid region) grow nasty mould. But maybe
you're doing decorative work that will never get
wet and none of this matters anyhow. In that case,
ignore this paragraph.

Okay--the spinnerness issue: First, if you haven't
done this, throw some plates, cut them off and let
them dry a bit. Trim your foot ring, and then wire
them in half. If the thickness of the base is much
varied from place to place, this could be your
problem. Usually the center will tend to be
thinner because the cutting wire will unavoidably
bow upward while you're cutting off the plate.
When you're slicing that plate off the bat, hold
the wire as taut as you physically can. This
helps, but will never completely eliminate the
problem, so remember, when you're trimming, that
the middle isn't going to be as thick as the
edges. You can't, in my experience, make thrown
plates with as thin a walls as you can get away
with if you're making, say, cups or bowls. They
will almost always warp. So give them a little
more bulk. They'll also survive daily use better
this way.

You could go to plaster bats, and allow the plates
to pop off of their own accord, eliminating the
need for cutting them off. I've had people tell me
I still need to cut the plates off, but in my
experience, a cutting wire is not necessary with
plaster bats. Bit of a hassle, though, making and
storing plaster bats.

I'm thinking of Vince's suggestion of using canvas
squares for smaller pots. He cuts squares to size,
then sticks them to the wheel head or to a bat for
making cups, etc. You just lift the whole square
off when the cup is done. You wouldn't want to do
that with a plate, because the base would warp, of
course. But I wonder about using a canvas piece as
a separator. Maybe it would work. You could just
stick the bat-sized canvas to your bat, then
remove the whole thing. Hopefully, when the plate
is leather hard, you could lift it off with the
canvas, thus avoiding the need for a cutting wire.
If you try this, let us know how it works. I think
I'll try it myself. Whoa! Cool idea! All right,
Cindy! Of course, if this does work, I'm
sure someone else has already done it.

As for drying; you're right to say that plates
need slow drying. Another thing that seems to help
me in drying is to use clay with added grog. I
haven't done any scientific studies, but I seem to
have better results in large pots and pots with
wide bases if I use maybe one to three cups of
grog to 35 lbs of clay. I use less for plates than
I do for mondo pots. Actually, I just dump some
grog into the pugmill. However much feels good to
me. But don't tell anybody, okay?

Get yourself a sheet of drywall (sheet rock) and
cut it to the size of your drying shelf. It's
cheap and easy to cut. If you're into salvage, ask
for some scraps at any building site you chance to
drive by. For cutting, you can use a box cutter.
(But remember to take the box cutter out of your
purse if you go to the airport.) Tape the edges
with duct tape so you don't get crumblies into
your clay, and lay it on your shelf. This is great
stuff for drying plates, tiles, and well,
anything, for that matter. Drape a sheet of
plastic over the plates if you need to. Maybe tuck
it in. You'll have to fine tune this part to the
moisture level in your studio. I don't like to
turn my plates over because I'm afraid they'll get
saggy bottoms, but lots of people do turn them
over. You probably won't have to, using the
drywall board, however you may want to move them
about a little, until they stop leaving little
damp spots.

Then, as you probably have noticed, you really do,
must, have to--have to, fire your plates on a
nice, flat, non-warped kiln shelf. Fire them nice
and slow. You're a potter, very Zen, you know.
Potters should never be in a hurry. (Yeah, right.
;) ) Okay, that's it. All I can think of. Let us
know if any of it works for you.

Best wishes,

Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
cindy@earthen-vessels-pottery.com
http://www.earthen-vessels-pottery.com

Dannon Rhudy on sun 11 nov 01


.Cindy said:

......>I'm thinking of Vince's suggestion of using canvas
>squares for smaller pots. He cuts squares to size,
>then sticks them to the wheel head or to a bat for
>making cups, etc. You just lift the whole square
>off when the cup is done. You wouldn't want to do
>that with a plate, because the base would warp,.....

Indeed, Cindy, they DON'T warp. Or at least, if they
do they flatten right back out again when you put the
canvas down. I do this all the time, with no problems.
For really large pieces, platters 20" or so, I leave them
on the bat and draw the wire tool UNDER the canvas.
Works fine. Soon as the rim is ready, I turn them over
onto a bat, and peel off the canvas. Perfectly flat foot,
makes trimming easy. I recommend canvas bats for
nearly any large piece, bowls and all. If you've already
got plaster, it works fine. If not - well, canvas doesn't
take up much room, and is cheap and extremely long
lasting. Easy to make - I tear to the right width, then
across to make squares, cut the corners off (I don't like
them to flap around). If they're smaller than the bat,
I don't cut the corners. If the bats are really bit, 20" or
more, I take the trouble to make round ones. There is
no reason for that, it is just what I do.

regards

Dannon Rhudy

Cindy Strnad on sun 11 nov 01


Wow, thanks for the info, Dannon.

See, I *knew* I couldn't have been the first one
to think of that. But how do you pick up the large
plates (not the 20 inchers, but the ones you don't
use a bat for) without them sagging all over the
place? You must have some canvas hanging over the
edge for that? Or do you just lift the edge of the
plate up and slip your hands under?

Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
cindy@earthen-vessels-pottery.com
http://www.earthen-vessels-pottery.com

Rowdy Dragon Pottery on mon 12 nov 01


Is this list great, or what? Just did a small run of platters this weekend
and was thinking about how to address a problem with my bats. The 24" bats
I use are sturdy, and with the underside laminated too the pin hole appears
to hold up well. But no matter how I cut the platter off the bat, the
laminate never really wants to release the piece cleanly. I've put up with
the extra work to get them off because my success rate with the pieces has
been near perfect. Even though I own a Dannon Rhudy original canvas bat, I
hadn't thought of trying them on pieces of this size and weight. I'll try
them on my next run. I haven't bought canvas before. Is there a special
weight of canvas that functions best?

Neil Berkowitz
Seattle

At 09:21 AM 11/11/01 -0600, Dannon wrote:
>.Cindy said:
>
>......>I'm thinking of Vince's suggestion of using canvas
> >squares for smaller pots. He cuts squares to size,
> >then sticks them to the wheel head or to a bat for
> >making cups, etc. You just lift the whole square
> >off when the cup is done. You wouldn't want to do
> >that with a plate, because the base would warp,.....
>
>Indeed, Cindy, they DON'T warp. Or at least, if they
>do they flatten right back out again when you put the
>canvas down. I do this all the time, with no problems.
>For really large pieces, platters 20" or so, I leave them
>on the bat and draw the wire tool UNDER the canvas.
>Works fine. Soon as the rim is ready, I turn them over
>onto a bat, and peel off the canvas. Perfectly flat foot,
>makes trimming easy. I recommend canvas bats for
>nearly any large piece, bowls and all. If you've already
>got plaster, it works fine. If not - well, canvas doesn't
>take up much room, and is cheap and extremely long
>lasting. Easy to make - I tear to the right width, then
>across to make squares, cut the corners off (I don't like
>them to flap around). If they're smaller than the bat,
>I don't cut the corners. If the bats are really bit, 20" or
>more, I take the trouble to make round ones. There is
>no reason for that, it is just what I do.

Steve Mills on tue 13 nov 01


Fascinating; when I first started production throwing I couldn't afford
bats (in those days they had to be marine ply, anything else fell to
pieces...animal glues), hadn't heard of canvas bats, taught myself how
to take 10 in or 12 in plates straight off the wheel without wrecking
them! threw them with narrow-ish rims about 1/4 in thick, wire off,
scrape hands semi-dry, ease up the edge and walk the fingers underneath
'till the plate is on the front of the fingers in a sort of V shape,
lift of and lay on the pot board, letting the edges drop the last inch
to straighten them out, flatten them finally upside-down just before
trimming.

Steve
Bath
UK


In message , Cindy Strnad writes
>Wow, thanks for the info, Dannon.
>
>See, I *knew* I couldn't have been the first one
>to think of that. But how do you pick up the large
>plates (not the 20 inchers, but the ones you don't
>use a bat for) without them sagging all over the
>place? You must have some canvas hanging over the
>edge for that? Or do you just lift the edge of the
>plate up and slip your hands under?
>
>Cindy Strnad
>Earthen Vessels Pottery
>RR 1, Box 51
>Custer, SD 57730
>USA
>cindy@earthen-vessels-pottery.com
>http://www.earthen-vessels-pottery.com

--
Steve Mills
Bath
UK

Jan McQueary on fri 16 nov 01


Canvas may help if you want to lift the pot off the bat right away, but I
have used old window shade material and also the (dacron?) paper they
wrap houses with before putting on the siding. Not sure what that's
called. Just put slurry on a bat, press the fabric on the slurry. Then
smooth it down with a rubber rib moving out from the center while the
wheel turns.

Jan McQueary

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