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tile cracks

updated mon 20 jul 98

 

Kim Marie on thu 16 jul 98

Wondering if i'm right about what i did wrong.

I have the book Handmade Tiles by frank G. (can't remember the correct
spelling of his last name and book is in my studio) I'm starting to
experiment with the process. I sliced some slabs from a fresh bag of my
standard 112 clay, put the slabs wrapped in plastic, between 2 pieces of
drywall so they would set up slowly. They were wonderfully leather hard when
I cut them to size and bevelled the edges. I then left the plastic off an
set them on a piece of the drywall. It only took about 3 hours for all of
them to develop cracks in the middle.

I was thinking that the transition of being in plastic to being exposed to
open air was too much for the guys. However, the cracks were 's' cracks
which, from what I've read, usually signifies a lack of compression. If this
is the case I figure it's because of I just sliced it from a block of clay
(I don't have a slab roller)

Any ideas or suggestions?

kim

Earl Brunner on thu 16 jul 98

I have also tried to make slabs by slicing, straight from the bag and have had
similar cracking problems. When working with large groups of children and
little equipment it seemed like a good idea, we had disastrous results. I
would also be curious about anyone's thoughts on this. Earl Brunner

the Gallagher's on thu 16 jul 98

> it's because of I just sliced it from a block of clay
(I don't have a slab roller)

Any ideas or suggestions?

kim

You can cut from your block of clay and then roll out with a kitchen rolling
pin, placing the clay between two wood pieces the thickness you desire.
Keeping the rolling pin on the wood, roll, then turn the slab and roll again,
compressing the clay. This should help.

Michelle
in Oregon

Chris Giorgetti on fri 17 jul 98

Earl .... I'll agree with Michelle in Oregon. Cutting slabs from the clay
block, rolling with a rolling pin between 2 sticks to desired tile thickness=
is
the only way I've ever made my tiles. I use a simple wooden kitchen rolling=
pin
available anywhere. Never had a cracking problem. I do lots of terra cotta
tiles, and dry them between pieces of sheetrock, flipping the sheetrock over
from time to time. No cracks, warped corners or other weirdness. I take =
wet
tiles (6=22x6=22 on a piece of canvas) to the fairs so kids can imprint =
their hand
or anything else in it. The =22sheetrock sandwich=22 goes home with me =
each day
for drying, etc. This is big with parents (and pet owners).

Chris Giorgetti
Lotsa Pots=21
Oakley, CA


-----Original Message-----
From: Earl Brunner =5BSMTP:BRUNNEREC=40aol.com=5D
Sent: Thursday, July 16, 1998 7:12 PM
To: CLAYART=40LSV.UKY.EDU
Subject: Re: tile cracks

----------------------------Original message----------------------------
I have also tried to make slabs by slicing, straight from the bag and have =
had
similar cracking problems. When working with large groups of children and
little equipment it seemed like a good idea, we had disastrous results. I
would also be curious about anyone's thoughts on this. Earl Brunner

amy parker on fri 17 jul 98

At 10:11 PM 7/16/98 EDT, you wrote:
>----------------------------Original message----------------------------
>I have also tried to make slabs by slicing, straight from the bag and have had
>similar cracking problems. When working with large groups of children and
>little equipment it seemed like a good idea, we had disastrous results. I
>would also be curious about anyone's thoughts on this. Earl Brunner
>

I too sliced clay for school projects, but found it necessary to level it
off with a rolling pin, since I didn't slice very evenly, and we had no
cracks, so it probably is a compression thing.
amy parker Lithonia, GA
amyp@sd-software.com

Laurel Carey on fri 17 jul 98

Earl Brunner wrote:
>
> ----------------------------Original message----------------------------
> I have also tried to make slabs by slicing, straight from the bag and have had
> similar cracking problems. When working with large groups of children and
> little equipment it seemed like a good idea, we had disastrous results. I
> would also be curious about anyone's thoughts on this. Earl Brunner

i had some bagged clay that froze and thawed - i saw it had broken apart
along spiralling lines. i presume this is from the spiral motion in the
pugmill, and thus you get "s" cracks just as with thrown items that have
not been compressed and/or dried too fast.

laurel

Andrew Lubow on fri 17 jul 98

You're right about slicing them as being the cause of your cracking. Roll
out a slab of clay with a rolling pin and two would strips as height gauges.

I prefer to build a mold frame the size I want out of 1"X2". Then I cut a
piece of plywood to to fit the interior as a floating floor of the frame.
Your raw tile's thickness is determined by how thick a piece of plywood you
use. Place a piece of cut magazine paper to cover the floor of the mold.
This acts as a release agent. Put a piece of clay in it and compress the
clay using a piece of scrap plywood that lays totally over the frame by
hitting it with a rubber mallet. Excess clay can be trimmed with a wire.
Push up on the floating floor and your tile pops out

MR ROBERT J MILLING on fri 17 jul 98

I have found that I have much less problems with cracking if I slow
down the drying. I put the tiles on sheet rock and tent with plastic.
I slowly dry them and slowly fire them. Helps a lot. Anne Milling

Janet or Michael Francoeur on fri 17 jul 98

I use Sandy Bottoms clay from highwater for tiles, it has some grit in it
and I slice it from the bag and roll it on to canvas with a rolling pin,
when I get it the thickness I want I transfer it to dry wall and trim to
shape then put another piece of drywall over it. Sometime at leather hard I
impress a pattern into it and again place it between the drywall till bone
dry or close to it. No cracks. The only time I've had cracking is if it is
too thin like1/8" ( I usually roll them to just less than 1/4 or one time
like a dummy I put it on the drywall and rolled just a little bit more,
which really smashed it into the drywall & they stuck and cracked terribly.
janet francoeur
----------

Richard Burkett on sat 18 jul 98

At 10:11 PM 7/16/98 EDT, you wrote:
>----------------------------Original message----------------------------
>I have also tried to make slabs by slicing, straight from the bag and have had
>similar cracking problems. When working with large groups of children and
>little equipment it seemed like a good idea, we had disastrous results. I
>would also be curious about anyone's thoughts on this. Earl Brunner
>

I too sliced clay for school projects, but found it necessary to level it
off with a rolling pin, since I didn't slice very evenly, and we had no
cracks, so it probably is a compression thing.
amy parker Lithonia, GA
amyp@sd-software.com

Timothy Dean Malm on sat 18 jul 98

I believe the cracking stems from the pugmill extruding the pug with a
twist.

On Sat, 18 Jul 1998, Amy Parker wrote:

> At 10:11 PM 7/16/98 EDT, you wrote:
> >----------------------------Original message----------------------------
> >I have also tried to make slabs by slicing, straight from the bag and
>have had
> >similar cracking problems. When working with large groups of children and
> >little equipment it seemed like a good idea, we had disastrous results. I
> >would also be curious about anyone's thoughts on this. Earl Brunner
> >
>
> I too sliced clay for school projects, but found it necessary to level it
> off with a rolling pin, since I didn't slice very evenly, and we had no
> cracks, so it probably is a compression thing.
> amy parker Lithonia, GA
> amyp@sd-software.com
>

cheryllitman@juno.com (Cheryl L Litman) on sat 18 jul 98

For me, cracking of slabs wired off straight from the bag had to do with
several factors, the clay I used, how I dried it and how I fired it. My
dark brown clay always cracked, a white and a light brown mostly didn't.

At this year's summer art camp, I started placing the pieces on some
ultra thick cardboard to dry after the kids worked on them rather than on
plywood. This past week I put both partially dried and totally wet
pieces straight into the kiln to force dry but sprinkled sand (cheap
sandbox sand from Home Depot) on the shelf under the pieces - not one
cracked as compared to last year - even the dark brown clay! The slabs
were about 8"x6". Several people on the list had mentioned using sand
under slabs to prevent cracking and it worked for me. I think that the
cracking has to do with uneven drying and parts of the slab catching on
the shelf instead of sliding. The sand allows the slab to slide a bit.

Cheryl Litman
Somerset, NJ
email: cheryllitman@juno.com

On Thu, 16 Jul 1998 22:11:54 EDT Earl Brunner writes:
>----------------------------Original
>message----------------------------
>I have also tried to make slabs by slicing, straight from the bag and
>have had
>similar cracking problems. When working with large groups of
>children and
>little equipment it seemed like a good idea, we had disastrous
>results. I
>would also be curious about anyone's thoughts on this. Earl Brunner
>

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