Float Glass is cracking

[Stacey]

Hi All,
I'm trying to make pocket vases using float glass. 1/8 inch on the bottom layer and 1/4 on the top. They measure 6x12 with a 1/2 inch fiber blanket in between to form the pocket. I've used 14 guage copper wire to use as hangers. My firing cycle is as follows. 250dph to 750. Hold 10 min. 9999 to 1500 hold 10 minutes. 9999 to 1030 hold 30 minutes. 20 dph to 960 hold 30 minutes. 100 dph to 750. Then 200dph to room temp. 3 out of four cracked around the copper the 4th cracked across the middle. Please help me. I'm on a deadline. Thanks Stacey

[Barbara Cashman]

Stacey, is there a reason you are not using 1/4" on the bottom also? The glass *may* not be compatible. Otherwise, your schedule seems ok. Bert will probably chime in and give you more info. - Barbara

[Colin & Helen]

Hello Stacey.

My moneys on compatibly....I use a lot of 2 and 6 mm float if I fuse 3 sheets of 2mm fused together then add extra 2mm as decoration ..no problems at all......if I fuse the 2mm decoration onto a single 6mm sheet . .........you can be sure it will crack............ so why not fuse two sheets 1/8 for the top and use just a single sheet of the same glass for the base

Colin

[Tony Smith]

A good rule of thumb for float is that if it isn't from the same sheet, or at least from the same case, then you may have a compatibility problem. Not all float glass is compatible.

Tony

[Jerry Barnett]

I do not use float, but would not go from 750 to 1500 as fast as possible with 1/2" fiber blanket shielding part of the bottom glass. Jerry

[Bert Weiss]

Hi All,
I'm trying to make pocket vases using float glass. 1/8 inch on the bottom layer and 1/4 on the top. They measure 6x12 with a 1/2 inch fiber blanket in between to form the pocket. I've used 14 guage copper wire to use as hangers. My firing cycle is as follows. 250dph to 750. Hold 10 min. 9999 to 1500 hold 10 minutes. 9999 to 1030 hold 30 minutes. 20 dph to 960 hold 30 minutes. 100 dph to 750. Then 200dph to room temp. 3 out of four cracked around the copper the 4th cracked across the middle. Please help me. I'm on a deadline. Thanks Stacey

Stacey

Aside from the obvious possible incompatibility issue, my guess is that the copper is too heavy a guage especially with 2 different thicknesses around it. I think you have a better shot using the same thickness on both sides. That solves compatibility and expansion around the copper issues. If both sides being the same glass doesn't solve it I would use a thinner guage of copper.

[Brian and Jenny Blanthorn]

Hi All,
I'm trying to make pocket vases using float glass. 1/8 inch on the bottom layer and 1/4 on the top. They measure 6x12 with a 1/2 inch fiber blanket in between to form the pocket. I've used 14 guage copper wire to use as hangers. My firing cycle is as follows. 250dph to 750. Hold 10 min. 9999 to 1500 hold 10 minutes. 9999 to 1030 hold 30 minutes. 20 dph to 960 hold 30 minutes. 100 dph to 750. Then 200dph to room temp. 3 out of four cracked around the copper the 4th cracked across the middle. Please help me. I'm on a deadline. Thanks Stacey

Stacey

Aside from the obvious possible incompatibility issue, my guess is that the copper is too heavy a guage especially with 2 different thicknesses around it. I think you have a better shot using the same thickness on both sides. That solves compatibility and expansion around the copper issues. If both sides being the same glass doesn't solve it I would use a thinner guage of copper.

It is one of the great joys in life 2 solve problems with a deadline approching

But it is when I get my best Cheetin Technology developments

Consider multy strand copper wire

[Judy Schnabel]

Stacey,

I fire quite a bit of float myself and use the 1030 temperature for my annealing point.

Is there a reason why you are holding for 30 minutes at 960?

Inquiring minds want to know.

Judy

[Lynne Chappell]

I had nothing but trouble with pocket vases. Lost at least half. And I wasn't using any wire imbedded in them. There could have been some compatibility issues as I was using regular Spectrum stained glass, but the cracking happened with different glasses and I've never had that much trouble with regular Spectrum for other applications. It is the insulating nature of the fiber in the pocket. The bottom glass doesn't get nearly as much heat except on the exposed edges so its tricky. I guess you have to go really slow and anneal very carefully. I just quit making them.