Carty Ellis on thu 30 nov 06
I seem to remember readint that rolled slabs should be rolled twice , second
time at 90 degrees from the first roll to reduce tendencey of slab to behave
like a wood plank and warp on drying and firing. Or is twice through the
machine - once forward and once backwards enough? (recent experience
indicates to me that the 90 degree is best - and just checking to see if I
added some inadvertant variable to the process - why one project came apart
with warping and one didn't).
Vince Pitelka on thu 30 nov 06
Carty Ellis wrote:
">I seem to remember reading that rolled slabs should be rolled twice ,
second
> time at 90 degrees from the first roll to reduce tendencey of slab to
> behave
> like a wood plank and warp on drying and firing. Or is twice through the
> machine - once forward and once backwards enough? (recent experience
> indicates to me that the 90 degree is best - and just checking to see if I
> added some inadvertant variable to the process - why one project came
> apart
> with warping and one didn't)."
Carty -
The objective is to cross-roll at 90 degrees to the original direction in
order to eliminate linear grain structure. For the very best slab with the
least chance of warping or curving from clay memory, flip it over and cross
roll in both directions on both sides. It's worth the time, and it's very
easy to do once you have it sandwiched between two layers of canvas.
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Catherine on fri 1 dec 06
Now you tell me! I am constructing a sort of box roughly 12" x 24".=0D
This "mesa island" has 4" to 6" high walls/cliffs that undulate irregular=
ly =0D
around the perimeter. The top and bottom slabs will have=0D
reinforcing members inside this box-like structure. The reinforcing =0D
members will vary on the upper edges to give the surface/top slab a more=0D
landscape-like appearance.=0D
=0D
About the slabs........ a certain thickness is needed for integrity. =0D
Next time, I should start with maybe a slab roller 1/2" thickness, reduci=
ng =0D
slightly with each change of position to achieve the necessary 3/8"? =0D
Otherwise, there will be no pressure on the slab.=0D
=0D
BTW, the "mesa box" is the beginning of the project, not the terminal eve=
nt.=0D
=0D
Catherine in warm again Yuma, AZ=0D
=0D
-------Original Message-------snip..........=0D
=0D
From: Vince Pitelka=0D
Subject: Re: Rolled slabs and drying warp=0D
=0D
Carty Ellis wrote:=0D
">I seem to remember reading that rolled slabs should be rolled twice ,=0D
second time at 90 degrees from the first roll to reduce tendencey of sla=
b
to=0D
> behave like a wood plank and warp on drying and firing. Or is twice
through=0D
the machine - once forward and once backwards enough? (recent
experience=0D
> indicates to me that the 90 degree is best - and just checking to see i=
f I=0D
> added some inadvertant variable to the process - why one project came=0D
> apart > with warping and one didn't)."=0D
=0D
Carty -=0D
The objective is to cross-roll at 90 degrees to the original direction in=
=0D
order to eliminate linear grain structure. For the very best slab with t=
he=0D
least chance of warping or curving from clay memory, flip it over and cro=
ss=0D
roll in both directions on both sides. It's worth the time, and it's ver=
y=0D
easy to do once you have it sandwiched between two layers of canvas.=0D
- Vince
Vince Pitelka on fri 1 dec 06
Catherine wrote:
"About the slabs........ a certain thickness is needed for integrity.
Next time, I should start with maybe a slab roller 1/2" thickness, reducing
slightly with each change of position to achieve the necessary 3/8"?
Otherwise, there will be no pressure on the slab."
Catherine -
You do not have to thin the slab at all while cross rolling it to eliminate
grain structure. After you have rolled the slab to thickness with your slab
roller, re-roll it by hand at 90 degrees to the orginal direction while the
slab is still stuck to the canvas. If canvas is stuck to the slab, you can
hand-roll it very agressively and it will not get any thinner, especially if
there is canvas on both sides. In order to get thinner, the slab must
expand in length and/or width, and it cannot do that when it is stuck to the
canvas. The pressure of the rolling pin will still move the platelates
around, and you will be eliminating the linear grain structure.
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
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