Yet another crack...

[lmartine]

Hi,

I was making a mosaic-like fused project yesterday. Basically, I put on a 12.25 inch white BU 113 a layer of broken pieces from a previous melt (average: 1/4 inch thick); the pieces were separated by 1/16 to 1/8 inch so that I could see the white base between them. The melt was made using BU clear, white, red and marigold.

It looked pretty good this morning when I opened the kiln (70F): the soft fuse gave me just the look that I was after. I set the blank on the slumping mold, put on some devit spray and when I came back, the blank was split in two

The schedule I used was:
200 1000 20
100 1250 30
* 1400 05
* 900 120
50 800 00
100 700 00

Obviously, this is an anneal break. How do you suggest that I adapt the schedule next time?

Any suggestions on how to use the leftover pieces? Gluing then slumping is not an option, from reading everal posts on this board.

Cheers!

Lucie

[DonMcClennen]

I'd suggest your AFAP down to 900 might not be a good idea... your speeding thru part of the anneal zone. go AFAP to 1000F then down to 900 at 50F deg/hr

[DonMcClennen]

What is your slump schedule??

[Valerie Adams]

Just as a side note; devit spray (I'm guessing you're using SuperSpray?) needs to be fired to at least 1400° in order to fuse clear. I accidentally used it on some tack-fused pieces that only went to 1380° and it rendered them splotchy and dirty looking. Typically, it's used during your fuse, not your slump.

[lmartine]

Sorry for the confusion: I guess I should have mentioned that the schedule I posted was for a tack fuse. My blank cracked on the mold before I even programmed the kiln for the slumping...

I always thought that from a full or tack fuse temperature, it was AFAP to 900 as this was the (new) annealing target when using bullseye glass. I used to do AFAP to 960F. Should I go back to that temperature?

Lucie

[David Jenkins]

Still ... what Valerie said: Were you going to use the devit spray on the slump step? I guess that doesn't address the crack problem, but just wanted to know if you had a secret way of divitting during slumping.

[lmartine]

Beginner's luck I guess: I always used devit spray before slumping and everything comes out shiny.

But with stuff breaking for my last 3 loads, I guess Imy luck ran out

[JestersBaubles]

Are you sure the piece was completely cool? Could be you hit it with the devit spray and it cracked.

Long shot, but you never know...

Dana W.

[Laurie Spray]

sometimes in a pot melt you can have coe shift.......

when you pulled it out of the fuse was it totally cool?

your cool to 900 does not look like a problem to me.....

If it is a "tac fuse" with varying thickness that is probably the problem. Add more anneal for a piece like that......picture would help.

[Morganica]

I would agree with Laurie, it's probably the anneal. You're tacking 6mm (average) onto 3mm, total of 9mm thickness with only a single layer in spots. Plus, you've got red and marigold that's being tacked onto a stiff glass like white, so you need to treat the glass as if it's at least 18mm thick and possibly as if it's 27mm thick. IOW, anneal for 3/4 or even a full inch of thickness.

Marigold is one of my favorite colors, use it a LOT, but it's a fussy glass in a tack fuse. It'll get even fussier, possibly even shift a tad, in a potmelt, so I'd give it a lot of room in the anneal schedule. Right now you've got an anneal soak that would work for 12mm of glass (1/2 inch), and a downramp that's closer to what you'd use for 19mm (3/4 inch) of glass.

I'd suggest getting consistent with them--try at least the 19mm schedule, which means a 3-hour soak, then 45 dph to 800, 81 dph to 700, 270 dph to room temp. Personally, I'd be even more conservative and go for the 1-inch schedule because of the marigold/white combination, but that's just me.

If you're still getting breaks with a 1-inch annealing schedule, then you may need to resign yourself to the notorious hot color COE shift. You can test it by melting a bit of your potmelt onto a piece of clear, running a very conservative anneal and checking it through the polarizer. If you see strong halos, schedule changing isn't going to help.

(remember, btw, that your mileage may vary--this is in my kiln, with my processes)

[lmartine]

Thanks a million Cynthia! I really appreciate your response and especially, you taking the time to enlighten us, newbies!

I have another melt waiting on the sidelines to be fused in a panel. Of course, I used only red,marigold and white (I apparently love living on the edge for a newbie! ). I will follow your advice to a T, being definitely be ultra-conservative with the annealing, especially since that melt was most likely not annealed properly in the first place.

Lucie

[jim simmons]

Also, remember that this glass has to be warmed up REALLY REALLY SLOW
because it has probably not been annealed properly the first time.
Jim