WarmGlass.com

Hello !

With the link below you can see this glass (the 4 Seasons) on the wall( Then... okay), the first- and second breaking of the glass.

Assuming that the firing was OK, what can be the reason of breaking ? The first break was alreay after half an hour after attach on the wall, the 2nd the next day.

The "screws" were only with the hand lightly turned on.

Thank you in advance for your help !

Jan de Jong (Holland)

http://jandejong-glas.nl/?page_id=486

Could it be thermal shock due to the big panels having their lower sections soaking up the sun? The break in the piece on the right is higher in the panel because it looks like it gets more exposure to the heat bringing the battle lines higher. peace, haydo.
PS - could be wrong as I have been before.

Wow, this has got to be heartbreaking! I'm so sorry.

Perhaps vandals? It appears the glass might be hung in a public place.

Other than that, I'm thinking the panels were under-annealed. Counting the owl, it looks like you've got at least five or so layers of glass there, and since the owl and top components are tack-fused, there's even more stress than if they were full-fused. The same with the second break; the background is two layers, plus the branches, plus the leaves, so at least four layers there too.

Can you post your firing schedule?

Kinda looks like an anneal problem
See the kinda s curve in the crack?
Jim

I think everyone's on the right track: This looks like both an annealing problem and an installation issue.

First, the components are standing proud of the base glass, i.e., it is a tack-fuse, and those can require surprisingly slow anneal times to prevent introduction of stress. (So knowing the schedules would be helpful).

Second, the installation itself may be introducing stress in a couple of ways:
--If you have multiple screws holding a big piece of glass, and they don't exactly, precisely conform to the contour of the glass, the screws holding the glass panel to the wall more tightly may put some stress on the panel. If the glass already has some annealing stress, that could be enough to cause cracking.
--Glass can absorb heat and expand, so if one part of the panel is in full, strong sun while another is in shade, the temperature difference could be enough to add more stress, especially if it's tightly held in place by screws. Again, if the glass has annealing stress, that could increase the chance of a crack.

Hello ! Thank you all for your answers ! Firing programm below.

I did not personally fire, as my kiln is too little. A relative with a bigger kiln did fire (and he did make more glassworks for outside and attached them.....but always in parts... and not so big !)

@ Valerie Adams: Yes, a hard lesson ! No vandals, the glass hangs on a wall (garden) of my own house .
@ Morganica: The screws were NOT tightly held the glass in place ! No idea if they did follow the contour of the glass. Another question (to learn from it !): Could be the ONLY screw in the middle above be a "troublemaker" ?

Full fuse:: 0-540 C. ,160min; 54C.-798C., 45min; 798C.-798gC.,30min; 798gr-540C.,000min; 540gC.-540C.,30min; 540C.-438C., 000min
438C.-438C., 15min: 438C.-00C.; 0min
Tack fuse: 00C.-540C.; 160min; 540C-740C, 30min; 740C-740C, 20min; 740C-540C; 000min; 540C-540C, 25min; 540C-438C, 000min; 438C-438C, 15min;
438C-00C, 0min

I hope I can repair this piece as good as possible...... or is that not possible ? Idea: Glue the glass on "Trespa" and then hang it on another wall with some morning sun ??
Perhaps do you have other possibilities ?

Jan de Jong(Holland)

Jan,
Essentially you have no anneal cool at all. 530-438 should take about two hours for this tack fusing. 438-370 about one hr. And 370-40 about one hr. (Although it will take much longer for the kiln to cool than the hour.
Others may have other ideas, but you should review Bullseye's chart on annealing thick slabs.

@ Stephen Richard: Thank you for your answer. Yes, you are right..... no annealing. But.... I did not fire myself and very surprised that my relative used this programm !

But...... is there anyone please , who can give advise about my question to try to repair this piece ??

Gluing on "Trespa"........ possible ? And then hanging the piece on a place where there is almost no sun !

Other possibilities ? You will understand that I love to hang this piece (and understand the "breaks" will always be seen, also after reparation)

Jan de Jong (Holland)

Couldn't you use a silicone glue and attach the glass to a wood panel? That way you could hang it with hardware from the back, and you may be able to just glue to glass closely enough to minimize the cracks. Or, you could refuse and still attach to a back board.

I agree with Valerie. The piece is too well conceived and cheerful to not try to save. I think the added support a panel backing brings would make me feel more confident that it could withstand the stresses of an outdoor environment.

@ @ Valerie Adams and Vonon: Thank you for your answer !
Yes, in any case I will try to repair this piece...... but I use somewhat help: 1) The first break was repaired the same day: A blank System96 (as the rest of the used glass) (partly.... so not the whole piece !) UV glued on the break. Question: Can I re-fire the piece without problems through the glue ? 2) If yes....I will refire the 2 parts with the right annealing ! 3) After firing I will glue both parts on wood and I have this plan: I make the holes in the wood a very little wider as the (thickest) round part of the scewsystem, so that this wood will give help to hang this piece and I can it give at this place more help !(question: will this be enough to use the holes for the glass ??) 4) Question: With the new annealing ... can I take the risk to hang the piece on the same place (with sun and shadow ??) See for the screwsystem: http://jandejong-glas.nl/?page_id=486
Jan de Jong (Holland)

About point 1: I did contact Bert Weiss and he suggested to fire the UV-glued piece to 200-225 C. with a 15 min. hold. Good chance the glass will be seperated !! Thank you very much Bert !!

After cleaning and removing rest of the glue I can refire the piece. I will tackfuse this piece with a (fully) Blank Spectrum96 under it.

Question: The piece becomes 3 mm thicker, which programma for tackfuse do you suggest for Spectrum96 ?? Or do you think a tackfuse is not the way to go on ?
A fullfuse would be better, but I don't like that for this piece.

Another question: Can I hang the glass after the right firing hang on the same place (sun and shadow !) ???

I appriciate any help !!!

Jan

Hello ! I did glue the glass on "Trespa". Now on the surface I still must glue the breaks and I intend to do that with epoxy glue.
Now I wonder if it is a good idea (or not !) to put some Powder on this breaks to mask them ??? Will this mask the breaks or just make them worse ?
Anybody experience with this ? Jan