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I have been experimenting with laminating super thin slices of colored clay patterns onto both sides of a white sheet of clay.  All went well until after bisque firing ... when I rinsed them in water small confetti shaped pieces popped off with enough force to travel a couple feet away. Woke me up! Glazed and fired them to Cone 7 and washed them again using a little more caution ... and a couple more zinged off.

Needless to say, none of the work is for sale ...

... my prime suspect here is very tiny air pockets since the pieces were dry enough to fire for a couple weeks just waiting indoors for a kiln load. But ... there were no visible air pockets while in process. I might need to try slip between the color and the white to fill those little gaps.

Any other ideas?

EFDF6A58-EF0B-421F-BCCF-443CDB1EB722.jpeg

Marcia Selsor likes this

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Is there one colour it's mostly happening on? I don't think it's because of air bubbles/pockets. Think it's shivering.

Edited by Min
Forgot to add what I think it is.
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Chris:

earlier this year I was experimenting with 04 porcelain frit ware. I was trimming slots and in laying different color bands. The bands would crack, with some sections falling away. So I used some 04 clear glaze, watered down with an additional 50% water and lightly coated the areas where the bands were applied. The problem ceased after that; so I wrote it down as a bonding issue due to a lack of flux. You could simply add equal parts of sodium and potassium spars to water to accomplish the same goal. You do not want or need a lot, just enough to fuse the overlaid pieces. I do however find it curious that the problem did not show up until water was used to rinse. Sudden shock/ change in expansion? 

The yellow and blue bands are 1/8" in depth. Not exactly what you are doing, but along the same principle.. 

Removed pic.. Still cannot figure out how to down size them.

Edited by glazenerd
Removed pic..could not get it to resize.

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I got a reply on my ‘Color/Colour in Clay’ Facebook page from a person who is also experimenting with this. She was using vinegar in tap water and had the same issue. She switched to plain distilled water and it went away ... she thought maybe it was ‘lime pops’. Going to try it since I am using vinegar in tap water also.

Marcia Selsor likes this

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Hi Chris, I took a course with Curt Benzle this fall and learned a ton about working with thin colored clay.  He leads a fantastic workshop. Problems with things falling apart are usually that the clay is either too wet or too dry when joining. Since you're having problems with delaminating, my guess is that it is too dry when applied, or not evenly wet and you've got wet and dry areas.  How are you wetting the clay. Which side. How are you sealing them together. One idea that might help  would be to place all the layers between two pieces of cotton sheeting and gently roll and flip them, and roll  again. And you you might start a bit thicker than you want the finished product to be and roll  it down to the final thickness.  I'd love to know if this helps. Ruth

 

D.M.Ernst likes this

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I keep all of the clay on a damp towel under plastic so they match each other all the time. This is why it was so unexpected ... my clays played very nicely together during building ... I thought my problems would come from other places. As usual, Clay is the teacher! Thanks !!

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3 hours ago, Chris Campbell said:

I got a reply on my ‘Color/Colour in Clay’ Facebook page from a person who is also experimenting with this. She was using vinegar in tap water and had the same issue. She switched to plain distilled water and it went away ... she thought maybe it was ‘lime pops’. Going to try it since I am using vinegar in tap water also.

Are you using plaster in the process somewhere? Unless you are contaminating the clay with plaster I can't see how it would be this. Jeff Zamek article on lime pops here if you haven't already read up on this.

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No plaster anywhere in my work area. Maybe it’s not lime ... I have no clue.

Never have seen a pop like this ... it shoots out from the surface with an audible pop and travels a couple feet from the force of it. Happened as soon as the pot got wet. Going to try losing the vinegar, use distilled water and see what happens next time. I do love mysteries.

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If bits are literally flying from the pot, that would imply some sort of tension between layers, wouldn't it? Rather than just casually flaking off because there was merely an insufficient bond between two layers? Like Min said above, shivering.

Can you make the problem worse? That is, are you able to attack one of the affected pieces with a sharp tool, and flake more away? What happens if you apply thermal shock to one of the affected pieces - freeze 'n' heat?

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Sputty/ Joel: 

noted that above. Why did it occur when water hit the piece?  A " safe" assumption would be the shard was already loose, and just that mild shot of temperature change finished it off. Stains change COE, but to what degree has yet to be tested. (To my knowledge)

nerd

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OK ... this new image might help better chemistry minds than mine. This is only happening under one pattern, the others are fine. From the image it looks like air bubbles but if my application process is off, why is it only off under one pattern?? I'm not saying I do it all correctly, but all the others are fine.

Most of the action is happening under the pink which is Mason #6020 ... Manganese Alumina Pink Corundum, an inorganic pigment, is a reaction product of high temperature calcination in which Aluminum (III) Oxide and Manganese (III) Oxide in varying amounts are homogeneously and ionically interdiffused to form a crystalline matrix of corundum. Its composition may include P205 as a modifier.

This needs brighter minds than mine chemistry wise.

IMG_3624.JPG

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49 minutes ago, Chris Campbell said:

Manganese Alumina Pink Corundum, an inorganic pigment, is a reaction product of high temperature calcination in which Aluminum (III) Oxide and Manganese (III) Oxide in varying amounts are homogeneously and ionically interdiffused to form a crystalline matrix of corundum. Its composition may include P205 as a modifier.

That's easy for you to say...

D.M.Ernst, RonSa and Chris Campbell like this

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So weird... Looks like a kind of blistering...  the behavior almost seems to suggest the presence of particles reactive to the water, like burnt lime (from calcium carbonate). This defect (even if not always is a defect) can occour in some clays for bricks, roof tiles and other outdoor objects. But hardly I can see this in a stain...

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5 hours ago, Sputty said:

Someone who has a clue might find some explanation in there, but that person is not me...

Here I can see no clue... Corundum is just aluminum oxide "doped" with other elements that give its color (in the case of the involved stain appears to be manganese)... sometimes corundum crystalline lattice can be tensioned and cracks because of big doping elements (i.e. chromium in ruby, and this is why it's so rare to have big rubies) but this is likely to happen only in big mono-crystals, and in this case, In my opinion, there is no explaination in the composition of the stain. Some foreign element\agent should be involved... 

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8 hours ago, Mark C. said:

looks like lime pops

whats in the water or slip for joining layers again?

About 1 tbsp  plain white Vinegar in 2 cups of water. Another potter said they had this problem and they used the vinegar water combo too.

As I try to remember process ... this was all done before Holiday madness ... I think this was strung out over days so the water application might have been oftener with time for the solution to sink into the clay .... maybe I actually had layers of vinegar??

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49 minutes ago, andros said:

Here I can see no clue... Corundum is just aluminum oxide "doped" with other elements that give its color (in the case of the involved stain appears to be manganese)... sometimes corundum crystalline lattice can be tensioned and cracks because of big doping elements (i.e. chromium in ruby, and this is why it's so rare to have big rubies) but this is likely to happen only in big mono-crystals, and in this case, In my opinion, there is no explaination in the composition of the stain.

I just knew someone would know what this physicsy/chemistry stuff is all about... image.png.6dac74fca802b5c0d9437e55941a7978.png

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Taking a brief look, I see several things that could cause or contribute. 

1. Corundum has an unique crystal structure as Andros pointed out.

2. It also has a very unique molecular mass at room temperatures; much different than " normal".which would translate  to differing COE to surrounding materials.

3. Synthetic corundum ( which stains are synthetic) can also produce pockets of mica crystals with the right conditions of flux/heat.

These might or perhaps not play a role. If I would venture a guess, I would go with door #2. Although it is a problem, one that doesn't.t fit the text books is always interesting to ponder.

andros and D.M.Ernst like this

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