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So I have a tiny hairline crack after bisque and I was going to try the spooze recipe I found here to fix it. 

1/3 parts dry clay powdered....any body...preferably the one you are using with no grog
1/3 parts heavy karo syrup
1/3 parts white distilled vinegar
drop of hydrogen peroxide

 

Should I be using dry powdered clay that has already been bisqued or does it matter? And I just bisque again after I apply it, correct?  I have some of the Amaco bisque fix  - and it works - but it fires so white, afraid it might not match

 

Thanks in advance! 

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So the spooze did not work.  :(  It worked on one really slight crack but there was a bigger one that it just didn't fill all the way.  I did it twice   I'm going to try the Amaco bisque fix now.  I'm a little worried because I have to fire to cone 6 now and the fixed crack will touch the lid - does anyone know if it will fuse it together? Is there something I can do?  Maybe sprinkle some powdered fired clay on top of where it touches? I'd hate to fire it not touching and then have it not fit. 

 

Thanks in advance.

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alumina is what will keep them separated.  never tried spooze.  maybe it will work.  most cracks that need filling should be overfilled just enough to allow the moisture in the correcting medium to dry out and shrink as it is fired.

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alumina is what will keep them separated.  never tried spooze.  maybe it will work.  most cracks that need filling should be overfilled just enough to allow the moisture in the correcting medium to dry out and shrink as it is fired.

 

Thanks for the response. I did over fill with the spooze.and it did work on the really thin crack but there was one that was pretty significant.  I filled it with bisque repair today will try firing it tomorrow.   I'm calling Amaco in the morning just to make sure I'm doing this properly. I can't make this thing again!

 

Never heard of alumina so I probably don't have any, Do you think kiln wash would work? It's a very tiny spot

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I'm updating this in case anyone else runs across the same problem.

 

So I called Amaco and they suggested another coat of bisque fix and then firing to cone 04 again with a piece of paper in between the lid and bottom.  I was worried about the color difference so I asked if a coat the spooze over the bisque fix might work and they said yes.   So it's in the kiln now.  Fingers crossed! Will update later.

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Try adding paper to the spooze mixture and blending... aka paper clay.

Also make absolutely sure your patch is totally dry before refiring.

Many folk here have had great success with spooze

Paper would burn out so why that was advised as a separating commodity surprises me.

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2 hours ago, Babs said:

Try adding paper to the spooze mixture and blending... aka paper clay.

Also make absolutely sure your patch is totally dry before refiring.

Many folk here have had great success with spooze

Paper would burn out so why that was advised as a separating commodity surprises me.

I just filled in the cracks with epoxy and kept it for myself and made her a new one. If it happens again - God forbid - I'll try adding paper.

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Pizzuti that Amaco stuff works.  Provided you have thin cracks.  Big cracks don’t work. I know someone who used it successfully in a wood kiln.  But thin cracks. 

A thin crack grows into a bigger one from bisque to glaze fire.  Worse still the cracks are so thin you only discover them after glaze fire.  

I am totally with Babs.  Why so many cracks.  That will be key.  

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11 hours ago, Babs said:

Worked out why it cracked?

can also add a bit of grog.

 

I really don't know. I spoke with someone at Seattle pottery who was very helpful, shocker I know :)! She said this clay was notorious for cracking. I think I just added too much water too many times, porcelain is so fussy. I haven't fired the new one yet but I made it differently. I made it all at once then dried it and I'm carving the top layer.  I also fired the first two in a pretty empty kiln which is apparently another mistake.

I did have another piece that I partially blew up in the kiln, I caught it and took it out, wet it down and put it back together with vinegar and clay, then fired it and it made it with no cracks, not porcelain though.

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10 hours ago, preeta said:

Pizzuti that Amaco stuff works.  Provided you have thin cracks.  Big cracks don’t work. I know someone who used it successfully in a wood kiln.  But thin cracks. 

A thin crack grows into a bigger one from bisque to glaze fire.  Worse still the cracks are so thin you only discover them after glaze fire.  

I am totally with Babs.  Why so many cracks.  That will be key.  

My cracks were too big I think. I don't know, it worked on a few but there were others that popped up. It's good practice anyway :)

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9 hours ago, pizzuti_ said:

My cracks were too big I think. I don't know, it worked on a few but there were others that popped up. It's good practice anyway :)

Right I'd change one thing at a time.

It you're carving that could be where the cracking starts.   For a variety of reasons..

You caught a pot midf iring????

Never used porcelain so someone familiar with its nuances can answer maybe.

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On March 29, 2017 at 12:19 PM, pizzuti_ said:

So I have a tiny hairline crack after bisque 

 

Thanks in advance! 

Tiny crack in porcelain; then later you state a larger crack in porcelain after bisq.

1. If on the bottom of the bowl: possible compression issue during throwing.

2. More likely blowing through the quartz inversion temp(563C) too fast during bisq fire.

3. Porcelain formulated without enough plasticizers, resulting in rapid dehydration. ( short clay)

which door would you like? 1-2-3 repairing cracks should not be the norm, but rather the exception.

T

 

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37 minutes ago, Babs said:

Right I'd change one thing at a time.

It you're carving that could be where the cracking starts.   For a variety of reasons..

You caught a pot midf iring????

Never used porcelain so someone familiar with its nuances can answer maybe.

I'm not doing any heavy duty carving, just details.

I had a piece in the kiln, vented, it was at 300, I had to run to the store so I turned off the kiln and shut the lid, came back opened the lid, it was in pieces.  So I wet it all down, put it back together with vinegar and clay and it fired fine a week or so later. It was not porcelain, just a white clay that fires to cone 6.

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Spooze can work well with hairlines in non-critical positions, and depending on the final use intended for the ware---but generally speaking-if it cracks, ditch it. There is no easier, softer way, as they say. Porcelain is prone to cracking-I've found one just has to accept a certain degree of "loss" due to fissures and fractures.  (I actually exploit it to work with my style, but that is not an approach suitable for most functional pieces.) Re: the piece you put back together-it may very well spontaneously shatter in the future, and personally I would not sell or give it to anyone. 

 

Edited by LeeU

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32 minutes ago, glazenerd said:

Tiny crack in porcelain; then later you state a larger crack in porcelain after bisq.

1. If on the bottom of the bowl: possible compression issue during throwing.

2. More likely blowing through the quartz inversion temp(563C) too fast during bisq fire.

3. Porcelain formulated without enough plasticizers, resulting in rapid dehydration. ( short clay)

which door would you like? 1-2-3 repairing cracks should not be the norm, but rather the exception.

T

 

The largest crack was on the bottom of the box. It's an animal box, oval really, with a lid.  I did not throw it. I fired very slowly, always do. This porcelain is the dove from seattle pottery, I have used it for years, never had cracking but I also never did my own firing. I also think that it was gas fired all the times before, I am using electric, not sure if that makes a difference, it fires better in gas, much nicer finish.

Edited by pizzuti_
.

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4 minutes ago, LeeU said:

Spooze can work well with hairlines in non-critical positions, and depending on the final use intended for the ware---but generally speaking-if it cracks, ditch it. There is no easier, softer way, as they say. Porcelain is prone to cracking-I've found one just has to accept a certain degree of "loss" due to fissures and fractures.  (I actually exploit it to work with my style, but that is not an approach suitable for most functional pieces.) Re: the piece you put back together-it may very well spontaneously shatter in the future, and personally I would not sell or give it to anyone. 

 

I know, I spent so much time on him it was hard to accept :) I'm keeping him for myself . He mocks me every day lol

The piece I put back together isn't porcelain, and it's very stable.

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Aaah pizzuti- you are learning to fire.  You’ve come to the right place . Lots of helpful souls on this board.

Do you candle? What temperature do you candle at before you start ramping up the kiln?

how dry is your ware?

btw my thoughts on pugging came about from trying to figure out cracks on the bottom of a big flat bowl I had taken every throwing precaution with.  

 

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10 hours ago, preeta said:

Aaah pizzuti- you are learning to fire.  You’ve come to the right place . Lots of helpful souls on this board.

Do you candle? What temperature do you candle at before you start ramping up the kiln?

how dry is your ware?

btw my thoughts on pugging came about from trying to figure out cracks on the bottom of a big flat bowl I had taken every throwing precaution with.  

 

That I am.... I've just started candling pieces, 200 degrees. I didn't have a full kiln and I don't think the piece dried evenly before either. We'll see how this time goes.

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On 7/12/2018 at 5:56 PM, pizzuti_ said:

The largest crack was on the bottom of the box. It's an animal box, oval really, with a lid.  I did not throw it. I fired very slowly, always do. This porcelain is the dove from seattle pottery, I have used it for years, never had cracking but I also never did my own firing. I also think that it was gas fired all the times before, I am using electric, not sure if that makes a difference, it fires better in gas, much nicer finish.

I have used that Dove porcelain.  Seattle Pottery would probably tell you it is not really intended as a hand-building clay.  You have to dry it really, really slowly before firing, and there is a good chance it will still crack.

Now when I use porcelain I use their CKK6, which is far less temperamental.

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3 hours ago, Gabby said:

I have used that Dove porcelain.  Seattle Pottery would probably tell you it is not really intended as a hand-building clay.  You have to dry it really, really slowly before firing, and there is a good chance it will still crack.

Now when I use porcelain I use their CKK6, which is far less temperamental.

They never told me that, but I never asked. :)  Is the CKK6 cone 6?

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This is what I use...adapted from Peggy Heer's  . 

 1:4 toilet paper to clay?  Soak toilet paper overnight, squeeze dry, add to dry clay, the same body as you are repairing..  Then add vinegar and a few drops of sodium silicate and mix with blender. I have repaired students' work with this as well as a sculpture of my own.\

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