John Rodgers on wed 10 sep 08
I have a lidded 5 quart ( :-) ) pot with a LOT of work into it. This
thing has been drying for a month in a warm room with dehumidifiers
running. It was perfect for bisque firing. Beautiful form, beautiful
ornate handles, a perfect fitting lid highly decorated.....and after
bisque firing right smack in the middle of the bottom is a hairline
crack that goes right through from inside to outside. I am so frustrated!!!!
Is there actually any way to effect a repair on such that will actually
hold up through a glaze firing??? I hope so. I glaze inside but not
outside on bottoms.
Anyone??
Thanks,
John Rodgers
Chelsea, AL
David Martin Hershey on thu 11 sep 08
John, let me guess: was it B-mix? ;^(
Best, DMH
David Martin Hershey
DMH Studio + Design
2629 Manhattan Ave #137
Hermosa Beach CA USA
90254-2447 310.379.6890
http://www.dmhstudio.com/
John Rodgers wrote:
> I have a lidded 5 quart ( :-) ) pot with a LOT of work into it. This
> thing has been drying for a month in a warm room with dehumidifiers
> running. It was perfect for bisque firing. Beautiful form, beautiful
> ornate handles, a perfect fitting lid highly decorated.....and after
> bisque firing right smack in the middle of the bottom is a hairline
> crack that goes right through from inside to outside. I am so
> frustrated!!!!
Antoinette Badenhorst on thu 11 sep 08
John; here is my way of fixing cracks. Some efforts work better than others. Mix up the following:
- slip from your clay, mixed up with paper; in other words paperclay from your clay body
- a shard of bisque of the same clay, grinded finely.
- Add to it sugar or some paper hardener like cmc to act like a glue
- A flux, like one of the ( lower melting) fritts or some low firing clear glaze.
I do not have measurements. I make sure that it has enough "tooth" from paper and particularly bisque powder, is sticky enough to stick and has enough glaze( flux) to help melt the area so that it can bond. It should be like a stiff paste.
Now; open the crack so that you can push clay right through the crack. You have to find the starting place of the crack and work from there. I usually use a dremel tool for this task.
Lastly I wet the cracked area to saturation ( to prevent the bisque to swallow the moist). Then I start pushing the clay mixture through the crack, making sure that I push the air out. Leave the mixture fairly thick on both sides of the crack to harden. Scrape the areas clean just before it becomes to hard to scrape off. Sugar can make it very very hard. As the clay shrink into the crack you will have to fill it up again from two sides this time. Lately I leave a thickened line on the crack and sand it off after I re bisqued it. Sometimes the crack re appear after the 2nd bisque firing. If that happens I trash the piece. Sometimes I touch it up with the crack mender. If it make it through a 2nd bisque firing, it will make it through the glaze firing. Make sure though that you fire it on something like silica sand or some other refractory material to act like little rollers under the pot.
I hope this info is useful.
--
Antoinette Badenhorst
www.clayandcanvas.com
www.studiopottery.co.uk
-------------- Original message ----------------------
From: John Rodgers
> I have a lidded 5 quart ( :-) ) pot with a LOT of work into it. This
> thing has been drying for a month in a warm room with dehumidifiers
> running. It was perfect for bisque firing. Beautiful form, beautiful
> ornate handles, a perfect fitting lid highly decorated.....and after
> bisque firing right smack in the middle of the bottom is a hairline
> crack that goes right through from inside to outside. I am so frustrated!!!!
>
> Is there actually any way to effect a repair on such that will actually
> hold up through a glaze firing??? I hope so. I glaze inside but not
> outside on bottoms.
>
> Anyone??
>
> Thanks,
>
> John Rodgers
> Chelsea, AL
William & Susan Schran User on thu 11 sep 08
On 9/10/08 10:02 PM, "John Rodgers" wrote:
> I have a lidded 5 quart ( :-) ) pot with a LOT of work into it. This
> thing has been drying for a month in a warm room with dehumidifiers
> running. It was perfect for bisque firing. Beautiful form, beautiful
> ornate handles, a perfect fitting lid highly decorated.....and after
> bisque firing right smack in the middle of the bottom is a hairline
> crack that goes right through from inside to outside. I am so frustrated!!!!
>
> Is there actually any way to effect a repair on such that will actually
> hold up through a glaze firing??? I hope so. I glaze inside but not
> outside on bottoms.
You will be even more frustrated when you spend the time attempting to
repair, glaze, load, fire and look at the bottom and find the crack has
enlarged to a big smile (I was going to write: find a big crack in it's
bottom...).
Cut your loses and trash it.
Large bottom forms - a great deal of stress on the bottom of the form -
weight of the pot and everything shrinking and moving. Certainly compression
of the bottom while making, but I think even more of an issue is "hidden"
changes in thickness. If the area for the bottom that turns up into the wall
is thicker than the center of the bottom of the pot, that can lead to a
great deal of stress that will be relieved at the thinnest area - the center
of the bottom.
Break that thing in half and check the thickness across the bottom.
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Mike Gordon on thu 11 sep 08
John, I have tried this with some success. Mix whatever glaze you are
using with some silica, and mix it into a paste, then with your finger
force it into the crack, clean up with a sponge and glaze over it.
. I never sold anything that I did this to, but it made it serviceable
for my own use.Mike Gordon
On Sep 10, 2008, at 7:02 PM, John Rodgers wrote:
> I have a lidded 5 quart ( :-) ) pot with a LOT of work into it. This
> thing has been drying for a month in a warm room with dehumidifiers
> running. It was perfect for bisque firing. Beautiful form, beautiful
> ornate handles, a perfect fitting lid highly decorated.....and after
> bisque firing right smack in the middle of the bottom is a hairline
> crack that goes right through from inside to outside. I am so
> frustrated!!!!
>
> Is there actually any way to effect a repair on such that will actually
> hold up through a glaze firing??? I hope so. I glaze inside but not
> outside on bottoms.
>
> Anyone??
>
> Thanks,
>
> John Rodgers
> Chelsea, AL
>
John Britt on thu 11 sep 08
John,
I would do what Adelaide Robineau did with her scarab vase.
Take some of your same clay that is bisque fired. (Actually she fired it
to cone 018.) And grind it up in a mortal and pestle and then add sodium
silicate to make a paste. Press that into the crack and fire.
The thinking is that you remove the physical water (hence the shrinkage)
from the clay body and the sodium silicate fuses it enough to hold.
She saved the 1000 hour scarab vase that way.
Hope it helps,
John Britt
www.johnbrittpottery.com/wks.htm
ncclayclub.blogspot.com
Lee Love on thu 11 sep 08
On Thu, Sep 11, 2008 at 7:41 PM, John Britt wrote:
> The thinking is that you remove the physical water (hence the shrinkage)
> from the clay body and the sodium silicate fuses it enough to hold.
>
> She saved the 1000 hour scarab vase that way.
Paper clay helps with shrinkage too. Instead of calcining and
grinding clay body, you could use grog or molochite, depending on the
body. That is what grog is.
--
Lee Love in Minneapolis
http://heartclay.blogspot.com/
http://mashikopots.blogspot.com/
http://claycraft.blogspot.com/
"Let the beauty we love be what we do.
There are hundreds of ways to kneel and kiss the ground." --Rumi
Eleanora Eden on fri 12 sep 08
HI John,
I read this post with great interest and would just like to emphasize the
wetting-the-pot part. Wetting the whole piece well would probably be
even better. Also think that leaving extra mender and sanding it later is
a good idea. Hey, I agree with all of it. It isn't too much trouble to save
a wonderful piece, and besides you learn something by trying it.
Eleanora
>John; here is my way of fixing cracks. Some efforts work better than others. Mix up the following:
>- slip from your clay, mixed up with paper; in other words paperclay from your clay body
>- a shard of bisque of the same clay, grinded finely.
>- Add to it sugar or some paper hardener like cmc to act like a glue
>- A flux, like one of the ( lower melting) fritts or some low firing clear glaze.
>
>I do not have measurements. I make sure that it has enough "tooth" from paper and particularly bisque powder, is sticky enough to stick and has enough glaze( flux) to help melt the area so that it can bond. It should be like a stiff paste.
>
>Now; open the crack so that you can push clay right through the crack. You have to find the starting place of the crack and work from there. I usually use a dremel tool for this task.
>
>Lastly I wet the cracked area to saturation ( to prevent the bisque to swallow the moist). Then I start pushing the clay mixture through the crack, making sure that I push the air out. Leave the mixture fairly thick on both sides of the crack to harden. Scrape the areas clean just before it becomes to hard to scrape off. Sugar can make it very very hard. As the clay shrink into the crack you will have to fill it up again from two sides this time. Lately I leave a thickened line on the crack and sand it off after I re bisqued it. Sometimes the crack re appear after the 2nd bisque firing. If that happens I trash the piece. Sometimes I touch it up with the crack mender. If it make it through a 2nd bisque firing, it will make it through the glaze firing. Make sure though that you fire it on something like silica sand or some other refractory material to act like little rollers under the pot.
>
>I hope this info is useful.
>--
>Antoinette Badenhorst
>www.clayandcanvas.com
>www.studiopottery.co.uk
>
>
> -------------- Original message ----------------------
>From: John Rodgers
>> I have a lidded 5 quart ( :-) ) pot with a LOT of work into it. This
>> thing has been drying for a month in a warm room with dehumidifiers
>> running. It was perfect for bisque firing. Beautiful form, beautiful
>> ornate handles, a perfect fitting lid highly decorated.....and after
>> bisque firing right smack in the middle of the bottom is a hairline
>> crack that goes right through from inside to outside. I am so frustrated!!!!
>>
>> Is there actually any way to effect a repair on such that will actually
>> hold up through a glaze firing??? I hope so. I glaze inside but not
>> outside on bottoms.
>>
>> Anyone??
>>
>> Thanks,
>>
>> John Rodgers
>> Chelsea, AL
--
Bellows Falls Vermont
www.eleanoraeden.com
John Rodgers on fri 12 sep 08
It was indeed!! And thereby hangs the tale. The stuff is notorious for
cracking - especially S cracks.But if you want to use it you just gotta
deal with it. And I do like ot use it.
John
David Martin Hershey wrote:
> John, let me guess: was it B-mix? ;^(
>
> Best, DMH
>
> David Martin Hershey
> DMH Studio + Design
> 2629 Manhattan Ave #137
> Hermosa Beach CA USA
> 90254-2447 310.379.6890
> http://www.dmhstudio.com/
>
> John Rodgers wrote:
>> I have a lidded 5 quart ( :-) ) pot with a LOT of work into it. This
>> thing has been drying for a month in a warm room with dehumidifiers
>> running. It was perfect for bisque firing. Beautiful form, beautiful
>> ornate handles, a perfect fitting lid highly decorated.....and after
>> bisque firing right smack in the middle of the bottom is a hairline
>> crack that goes right through from inside to outside. I am so
>> frustrated!!!!
>
>
gayle bair on fri 12 sep 08
John....
I have used B-mix ^5 almost exclusively for 9 years. I bitched about
it all the time. Since I like the way it throws and it's near
whiteness I continue using it.
A couple years ago I finally realized (think 2x4 here) & had to accept
that it needs patience.
I use hardiboard as ware boards. Anything with attachments rest in
tubs before and after assembly. No water sits in the bottom while
throwing and I am now throwing pretty dry (very little water). I
haven't had an S crack in years and now little to no cracks at joins.
I make a paper clay slip with magic water for joins that I have used
with success even on bisque.
Now that said I'm going to be getting ^5-6 porcelain as I might as
well be using that and get a real white claybody to decorate. I took a
class here last month and used several ^10 porcelains and damn.....
throwing & assembling was easier than the B-Mix. One body was horribly
short but the other was fabulous. Only problem was that I trimmed
right through 3 pieces so there's a learning curve there for me but
I'm going to give it a go!
Gayle Bair
Bainbridge Island WA
Tucson AZ
gayle@claybair.com
www.claybair.com
On Sep 12, 2008, at 12:40 PM, John Rodgers wrote:
> It was indeed!! And thereby hangs the tale. The stuff is notorious for
> cracking - especially S cracks.But if you want to use it you just
> gotta
> deal with it. And I do like ot use it.
>
> John
>
> David Martin Hershey wrote:
>> John, let me guess: was it B-mix? ;^(
>>
>> Best, DMH
>>
>> David Martin Hershey
>> DMH Studio + Design
>> 2629 Manhattan Ave #137
>> Hermosa Beach CA USA
>> 90254-2447 310.379.6890
>> http://www.dmhstudio.com/
>>
>> John Rodgers wrote:
>>> I have a lidded 5 quart ( :-) ) pot with a LOT of work into it. This
>>> thing has been drying for a month in a warm room with dehumidifiers
>>> running. It was perfect for bisque firing. Beautiful form, beautiful
>>> ornate handles, a perfect fitting lid highly decorated.....and after
>>> bisque firing right smack in the middle of the bottom is a hairline
>>> crack that goes right through from inside to outside. I am so
>>> frustrated!!!!
>>
>>
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