Lynn Korbel on fri 3 oct 97
Greetings!!
I recently threw some pots with saucers to contain plants. In the first
couple i forgot to put in the drainage hole and put it in while turning the
pots. In the others i put the holes in during the throwing process. Before
firing there were no indications of cracks--after firing all the drainage
holes have a tiny crack or two radiating from the drainage hole. My question
is why, and when is the best time to put the drainage hole in--or perhaps it
doesn't matter as all mine did crack anyway. I have some concern as i have
done some bonsai pots, put the holes in during the throwing process, and
cringe at the possibility of the cracks recurring. Is there a trick to
preventing cracks around drainage holes??? TIA
Best Wishes,
Lynn Korbel
on the Mississippi coast, where for the first time since last fall i have
dispensed with the canned air and have opened the windows to let in the
glorious fall ambiance :-)))
Brad Sondahl on sat 4 oct 97
Clearly clay is least likely to develop stress cracks at holes when it
is wetter, rather than drier. However the way you make the holes is
more likely the cause, than WHEN you make them. I've added holes to
bone dry planters successfully, but done it slowly. The tool I use
(inkpen point reversed, illustrated on my potterytips page, address
below) slices a hole without pressing outward. A drill bit, or just
poking a hole with a stick will exert outward pressure). I think there
are commercial holecutters that work on the same principle as mine...
--
Brad Sondahl
bsondahl@camasnet.com
http://www.camasnet.com/~asondahl/potterytips.html
PO Box 96, Nezperce ID 83543
"When it comes to dabbling, I'm just a dilettante..."
Cindy Morley on sat 4 oct 97
One thing my instructor showed me to do when I wanted planters was to not
completely cut out the hole. Basiclly just make perferated marks the size
and place where you want your hole and then after the bisque, just tap out
the hole. Make sure the perferations go all the way through the pot, and
put them relativly close together. I have never had any trouble with
cracking since then, but I have had to do a little smoothing of the hole
after I tap the center out. Hope this helps.
Cindy Morley
Fayetteville, Arkansas
On Fri, 3 Oct 1997, Lynn Korbel wrote:
> ----------------------------Original message----------------------------
> Greetings!!
> I recently threw some pots with saucers to contain plants. In the first
> couple i forgot to put in the drainage hole and put it in while turning the
> pots. In the others i put the holes in during the throwing process. Before
> firing there were no indications of cracks--after firing all the drainage
> holes have a tiny crack or two radiating from the drainage hole. My question
> is why, and when is the best time to put the drainage hole in--or perhaps it
> doesn't matter as all mine did crack anyway. I have some concern as i have
> done some bonsai pots, put the holes in during the throwing process, and
> cringe at the possibility of the cracks recurring. Is there a trick to
> preventing cracks around drainage holes??? TIA
> Best Wishes,
> Lynn Korbel
> on the Mississippi coast, where for the first time since last fall i have
> dispensed with the canned air and have opened the windows to let in the
> glorious fall ambiance :-)))
>
Cindy on sat 4 oct 97
Lynn,
When I make planters, I cut the drainage holes with a needle tool as I trim
the bottoms, and I've never experienced the cracking problems you describe.
I'm always careful to keep the bottoms of uniform thickness--maybe that
would help? Hope you find the way to fix your problems.
Cindy in Custer, SD
after firing all the drainage
> holes have a tiny crack or two radiating from the drainage hole. My
question
> is why, and when is the best time to put the drainage hole in--or perhaps
it
> doesn't matter as all mine did crack anyway.
Vince Pitelka on sat 4 oct 97
>doesn't matter as all mine did crack anyway. I have some concern as i have
>done some bonsai pots, put the holes in during the throwing process, and
>cringe at the possibility of the cracks recurring. Is there a trick to
>preventing cracks around drainage holes??? TIA
Lynn -
In the past I have done about eleven gazillion planters with separate
plates. I never had any problem with cracks around the drainage hole. Be
sure that you are compressing the bottoms of your planters very well. To
make the drain hole, I always used a piece of metal tubing of the desired
diameter, ground to a sharp edge on the end, to push through the bottom
right after throwing and before running the cutoff wire under the pot. If
you are using a fine-grained, gritless clay, that will increase the tendency
to crack. This has been discussed many times, but make absolutely sure you
are compressing the bottoms well, removing every trace of water from the
inside bottom of the pot when you are done throwing, and remove all water
from around the pot before you pull your cutoff wire under the pot. If you
do all these things, you should not have any problem with cracking around
the drain hole. Hope this helps.
- Vince
Vince Pitelka - vpitelka@DeKalb.net
Home 615/597-5376, work 615/597-6801, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
ray carlton on sun 5 oct 97
hi lynne i wonder if you should be looking at another clay body that has a
little better drying characteristics or add some fine grog to the original.
i don't think that timing when the holes go in is where it's at
At 10:30 03/10/97 EDT, you wrote:
>----------------------------Original message----------------------------
>Greetings!!
>I recently threw some pots with saucers to contain plants. In the first
>couple i forgot to put in the drainage hole and put it in while turning the
>pots. In the others ,,snip,,,pened the windows to let in the
>glorious fall ambiance :-)))
>
>
raycarlt@valylink.net.au
Ray Carlton
17 Reefton Drive
McMahons Creek Victoria Australia 3799
0359668443
David Hewitt on tue 7 oct 97
I would agree with Brad that the way you make the holes is more likely
to be the cause than when you make them, but I always do it at the
leather hard stage - unless by chance I have missed one and I have to
put it in later. I have found that this can be done by starting with a
very small pin hole and working up in size with different drill sizes.
Not, however, recommended. I make a range of oil burners which are
pierced with approx 1/4 inch holes and so I have pierced many hundreds
of holes and do not get any cracking. I could not find a commercial hole
cutter the size I wanted so use the plastic caps that are supplied with
ladies eye liner pencils. Cut the open end of the cap at an angle and
drill a hole a right angles through near the closed end. Put a nail
through this hole and tape it in. This makes a nice short piercing tool
and permits fast hole piercing.
In message , Brad Sondahl writes
>----------------------------Original message----------------------------
>Clearly clay is least likely to develop stress cracks at holes when it
>is wetter, rather than drier. However the way you make the holes is
>more likely the cause, than WHEN you make them. I've added holes to
>bone dry planters successfully, but done it slowly. The tool I use
>(inkpen point reversed, illustrated on my potterytips page, address
>below) slices a hole without pressing outward. A drill bit, or just
>poking a hole with a stick will exert outward pressure). I think there
>are commercial holecutters that work on the same principle as mine...
>--
>Brad Sondahl
>bsondahl@camasnet.com
>http://www.camasnet.com/~asondahl/potterytips.html
>PO Box 96, Nezperce ID 83543
>"When it comes to dabbling, I'm just a dilettante..."
>
--
David Hewitt
David Hewitt Pottery ,
7 Fairfield Road, Caerleon, Newport,
South Wales, NP6 1DQ, UK. Tel:- +44 (0) 1633 420647
URL http://digitalfire.com/education/people/hewitt.htm
Suzanne Storer on wed 8 oct 97
I solved cracking in my large platters by doing a variation of what Bill
Lizonbee (sp?) at Laguna Clay recommended. I add 5% pyrax, 5% wollastonite
and 5% red brick grog (my additon) to my slightly coarse cone 5 red clay
body that's not designed for making large pieces. Altering the clay body is
the only thing that worked after a year of flutzing around. It's relatively
easy with a pug mill.
Suzanne-in-Utah where snow's due tonight at 6000 ft. elevation.
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