It cracked AGAIN! - WarmGlass.com

It cracked AGAIN!

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Havi
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It cracked AGAIN!

Postby Havi » Mon Nov 12, 2012 8:15 am

Dear friends,
This time I attach close ups of the cracked areas in this work. I'd be more than grateful if anybody could explain why it happenned.
I refired the piece ,after the first cracks - I did a very conservative schedule.

It was absolutely OK when I took is out of the kiln Friday night.
Sunday morning I saw the cracks.
I shall try 'rescue' this by sawing away the bad areas. - if it stops cracking, then see what can be done with this .

All the glass is BE, the lavender background is BE1842 light neo-lavender shift tint - color which I like a lot. I just want to know whether I should not use it at all, or what?

CRACKS 005.JPG

CRACKS 006.JPG

CRACKS 007 - Copy.JPG


Thanks in advance,
Havi
Haviva Z
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DonMcClennen
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Re: It cracked AGAIN!

Postby DonMcClennen » Mon Nov 12, 2012 12:40 pm

I would not use this. It will only continue to self destruct. These pot melts/screen melts/high fires are experimental at best. With COE shifts and other complications they are often unreliable!
"The Glassman"

Brad Walker
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Re: It cracked AGAIN!

Postby Brad Walker » Mon Nov 12, 2012 1:30 pm

Most likely, this is incompatibility caused by prolonged hold at high temps (1700F/925C). Many Bullseye and Spectrum colors will shift COE after long soaks at high temps.

Havi
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Re: It cracked AGAIN!

Postby Havi » Mon Nov 12, 2012 1:54 pm

OK guys, DEAR guys,
I am very grateful for your responses. Honestly, many many thanks!

By now, this melt is sawn and the 'sick' areas are out! I shall see how the 'healthy' part will survive.

The point is, that this method is very representative of my emotions and being , and I would really love to develop it - if the glass allows me to -

I have patience. And shall continue experimenting,
My next firing will be on my Jen Ken kiln, which is a bit bigger -
I shall go only to 1600F as top temp. I have seen it recommended somewhere. Also I shall do a very slow annealling, both at soak and at the going down process.

However, do you rule out that this is because of the specific glass BE1842?
Eventually I shall experiment with this again, but if someone has particular knowledge about this it will be very helpfull.

Thanks a lot,
Havi
Haviva Z
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Brad Walker
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Re: It cracked AGAIN!

Postby Brad Walker » Mon Nov 12, 2012 1:59 pm

Havi wrote:However, do you rule out that this is because of the specific glass BE1842?


I can't comment on that specific glass, haven't used it in a high temp firing before. But there are a number of others that can be problematical. If that's the color you want, you'll just have to test and hope for the best.

Havi
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Re: It cracked AGAIN!

Postby Havi » Mon Nov 12, 2012 2:05 pm

Brad,
Somehow I was thinking that this BE18XX series, which was basically made for casting [am I right?] will be able to survive high temps better..............
I want to test more of them and see



Thanks for your respose
Havi
Haviva Z
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"Speed comes from the Devil" - (an Arabic proverb)
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Brad Walker
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Re: It cracked AGAIN!

Postby Brad Walker » Mon Nov 12, 2012 2:10 pm

Havi wrote:Somehow I was thinking that this BE18XX series, which was basically made for casting [am I right?] will be able to survive high temps better..............
I want to test more of them and see


As far as I know, the BE18XX series are just tints, mostly versions of other colors with less colorant. That probably makes them more suitable for thicker items, but not necessarily for high temperature firing.

Jeanne
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Re: It cracked AGAIN!

Postby Jeanne » Mon Nov 12, 2012 2:16 pm

Brad Walker wrote:Most likely, this is incompatibility caused by prolonged hold at high temps (1700F/925C). Many Bullseye and Spectrum colors will shift COE after long soaks at high temps.


What would be considered a "long" soak? I have done several wire melts recently with no problems. I am soaking at 30 minutes at 1700 (all the glass is down at this point). Am I lucky?

Havi
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Re: It cracked AGAIN!

Postby Havi » Mon Nov 12, 2012 2:26 pm

Actually I had 2 experiments
The first one soaked at 1700F for about 15 minutes, and is absolutely fine.
The second one soaked for 45 minutes, and cracked..............

However,
I refired this piece to 820C degerees, [1508F]
AND annealed very conservatively, so it cracked after 24 hours, instead of 2 hours in the first attempt. Seems to me, it has to be different reason,


thanks for your imput,
Havi
Haviva Z
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"Speed comes from the Devil" - (an Arabic proverb)
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DonMcClennen
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Re: It cracked AGAIN!

Postby DonMcClennen » Mon Nov 12, 2012 5:22 pm

I'll say it again......"these melts are a crap shoot!!"
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Brad Walker
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Re: It cracked AGAIN!

Postby Brad Walker » Mon Nov 12, 2012 6:11 pm

Jeanne wrote:
Brad Walker wrote:Most likely, this is incompatibility caused by prolonged hold at high temps (1700F/925C). Many Bullseye and Spectrum colors will shift COE after long soaks at high temps.


What would be considered a "long" soak? I have done several wire melts recently with no problems. I am soaking at 30 minutes at 1700 (all the glass is down at this point). Am I lucky?


It very much depends on the glass. Sometimes I can soak for an hour or more with no problem, sometimes only a few minutes hold will give you a problem. Some colors work, some don't. Sometimes a new sheet of a color that worked before doesn't work the way the old sheet did. Anytime you push the limits of what the glass is made to do, you run the risk of running into problems and you'll have to test on your own. I'm sure that's what Don means by a "crap shoot" -- sometimes it works well, sometimes it doesn't. You just want to minimize the time spent at the higher temps to the degree possible given the look you're going after.

twin vision glass
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Re: It cracked AGAIN!

Postby twin vision glass » Tue Nov 13, 2012 1:21 am

If you wrote to Bullseye I am sure they would give you the same information that some glass shifts at high temperatures. Does not matter if you try to refire as it has already changed with the high temp of the first time. Any thing you try will not bring it back to its original I do not believe. I am so sorry to say. BUT BUT if you hold LONGER at a lower temp of 1550 for 3 hours you will not change anything but you will get some wonderful effects as well. It all depends on how you suspend your glass and what it falls through to create just what you are doing at high tempts quickly but jeoprodizing the glass . I would so very much love you Havi to let Bullseye read this thread and have their team discuss it . Would that be O.K. I think we could all learn some things from this discussion.
Les

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Re: It cracked AGAIN!

Postby twin vision glass » Tue Nov 13, 2012 1:31 am

Image
Image
This was only taken to 1500 F.and held for 1 hour but it was cast through a one inch stainless steel mesh . I took ALONG time to get to top temp and held at 1230 F. for 2 hours on the way up. I went up slow so I could hold at low top temp and it all flowed nicely through the mesh. BUT you could get the glass to flow really wonderfully by placing the glass above the shelf at different levels to get great movement like you are getting without jeoprodizing the glass.
Here is the discussion on the Bullseye site. It might help .
http://www.bullseyeglass.com/index.php? ... 6449#p6449

Morganica
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Re: It cracked AGAIN!

Postby Morganica » Tue Nov 13, 2012 3:16 am

Havi wrote:Actually I had 2 experiments
The first one soaked at 1700F for about 15 minutes, and is absolutely fine.
The second one soaked for 45 minutes, and cracked..............

However,
I refired this piece to 820C degerees, [1508F]
AND annealed very conservatively, so it cracked after 24 hours, instead of 2 hours in the first attempt. Seems to me, it has to be different reason,


thanks for your imput,
Havi

Well...if 15 minutes at 1700F appears fine and 45 minutes at the same temperature doesn't, you've got a starting point for experimentation, assuming that the glass with less heatwork doesn't have any kind of incompatibility stress. I think that's a big assumption. The fractures could very well be heading out of the orange/yellow area, meaning that the usual suspects--reds/oranges/yellows--have shifted. But the colors are so dispersed in the images you've posted that it's hard to tell. Usually you see some kind of recurring pattern of breaks (like Xs) within in a particular color, or surrounding it. It's almost as if the piece is trying to push the incompatible glass out of the composition.

I don't think the time delay (2 hours vs 24) really indicates much--you could have had residual stress in the first attempt which exacerbated the incompatibility stress, so it cracked earlier. Or the second firing was well-annealed piece so it took longer for the cracks to show up. Or the cracks in the second piece could have started much sooner and just not have been as detectable until they'd grown a bit.

The problem is, when the glass has shifted, it's shifted, and the piece is pretty much lost.
Cynthia Morgan
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orittlandau
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Re: It cracked AGAIN!

Postby orittlandau » Tue Nov 13, 2012 8:33 am

maybe the high temp (1700) was the reason for the break in this earlier work too ?and not because it was stuck to the firebrick ??



viewtopic.php?f=2&t=39575

i agree with you less!! wonderful results can be achieved by reaching only 1500 temp. High temp can effect the glass in a way we even cant fix it in additional firing.
oritt

Havi
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Re: It cracked AGAIN!

Postby Havi » Tue Nov 13, 2012 11:48 am

Thanks Cynthia for chyming in. Thanks Donn, and Thanks Brad - -
And Les, I read your link to the BE froum.

I went all the way thru 45 minutes, actually because I thought more glass will get off the S. steel , and wanted to check that.
So I had my lesson. :? :oops:

I am going to write to Ted Sawyer, or one of the other guys at the Reseach and Education at BE, hopefully I shall learn some interesting info.

However, I am planning to do another firing, in my kiln where I have a pip hole, I shall plan the programme for 1700, but watch it very carefully from 1600 [if the redness of the heat allows], and see if I can continue before actually getting to 1700. In any case I wo'nt stay at 1700 more than 10 minutes at the most.

I like very much the results of this way of firing, I would like to continue this way. there are more challenges ahead - which excite me a lot.

Thanks again,
Haviva Z
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"Speed comes from the Devil" - (an Arabic proverb)
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Dairy Queen
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Re: It cracked AGAIN!

Postby Dairy Queen » Wed Nov 14, 2012 8:53 am

Havi,

Bigger hole-
Lower Temp-
Longer hold-

I forgot to send you (I went to corning for two weeks) a photo of home made clay grid. I have done lots of melts lately at 1480 for 5 hours. Hole needs to be bigger!

Good luck,
Rose
Love and luck make a wonderful lifestyle.

Haydo
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Re: It cracked AGAIN!

Postby Haydo » Wed Nov 14, 2012 9:49 am

Like anything we do with glass, success comes from experience. This is an idea for something that just can not be lost. I have a blue coccoon which looked the part until I found a part just before exhibition. It was foolish to have a pot melt form at one inch thick, I however allowed for thickness during component melding. Slapped on silicone to the back and a thin film to the show front just to get it out there. To remedy this problem I'll cold work the piece again to a higher standard and then encase it in a very thick slab of resin. From there it can self distruct all it likes. peace, haydo
Life is like a raft, so be like a rat!...Challenging being a captain type rat though, going down with each ship and all!!

Havi
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Re: It cracked AGAIN!

Postby Havi » Wed Nov 14, 2012 11:48 am

Dear Haydo!
I need a SYSTEM of working, not one time solution to a particular problem. You are very ingenious - this is good for you, and thanks for sharing this ingenuity. However, this can't work for me. I need and will probabley do a test to learn exactly what can be done, and how, and in what temrprature [exactly] so thanks again.

Dear Rose [finally I know your name] Dairy Queen
I was thinking of you the other day, thank you for chiming in.
I was thinking again about making clay mesh. [If I can, I'll post a photo of the mesh I made but never used]
Now I was thinking of making thick "noodles" and criss crossing them to create a mesh. Talked to a ceramicist friend, and she was worried that the clay will break under the glass while doing the melt. Can you please post or pm me a photo of your mesh? Can you comment about the danger of the clay breaking under the glass?
Why does the size of the hole make a difference in the breaking of the glass?

Thanks,
Havi
Haviva Z
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Havi
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Re: It cracked AGAIN!

Postby Havi » Wed Nov 14, 2012 4:43 pm

Dear friends,
As said before, I wrote a long letter to BE's department of Research and Education.
2 major things I'd like to share with you

a. BE does not have a chart for the change of viscosity in their glass, nor do they have a table of temp.s that indicate where the glass becomes incompatible.

b. BE recommends to do a test, its details I'll post in a minute - and to check exactly what happens with the glass one wants to use -
"…. take 1.25cm chips of all of the glasses that you are planning to use and place them on a 6.35 cm wide piece of clear test glass (Tekta or 1101) such that there is at least 2.5 cm of space between each chip and the edges of the glass. Then subject the test bar to the same heatwork that your process will subject them to. Include all firings. After each firing, view the tests for strain through cross polarized light – or see if they break. It takes a little time, but is much less painful than using a bunch of glass only to have a broken piece."
I got Ted Sawyer's permission to poste this here, only I apologise that the measurments are in metrical system - as it was basically written to me, who works in metrical system.
Can someone please translate those to inch system?

Personally , I am going to do so, and test as many glasses [colors] as I want to use.

Following the discussion here, I shall also target at a lower top temprature, between 1600 to 1650 not 1700. You read above that Dairy Queen even raises the temp. as "low" as 1480 - but stays 5 hours at that temp.]

I hope more people will participate and share their experiences - of which we shall all benefiet
[and excuse my terrible spelling]

yours,
with eternal gratitude,
Havi
Haviva Z
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"Speed comes from the Devil" - (an Arabic proverb)
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