Why did my pieces fully fuse rather than contour?

[Anne Marie Flaherty]

Hi there, I had previously used this below schedule to contour a bunch of 6 x 3 pieces and they worked perfectly, and then I did the same schedule for another load and all the pieces completely fused. On my third load I adjusted the schedule to the following and it still completely fused-any thoughts on how to get my pieces to contour? Thank you!
1st and 2nd schedule:
SEGMENT Rate Temp Hold
1. HEATING 1 300 1150 35
2. HEATING ll 200 1370 30
3. Heat to Forming Stage 400 1470 20
4. Anneal 1: 9999 950 60
5. Anneal II: 150 800 10
6. Cool Down 300 100 0

3rd schedule:
SEGMENT Rate Temp Hold
1. HEATING 1 300 1150 35
2. HEATING ll 200 1370 30
3. Heat to Forming Stage 400 1470 15
4. Anneal 1: 9999 950 60
5. Anneal II: 150 800 10
6. Cool Down 300 100 0

[DonMcClennen]

1470 is a full fuse schedule in most kilns.....If by the word "contour" you mean slump then you are 300F too high!

[Anne Marie Flaherty]

Thank you Don-

I don't mean slump, I just wanted some relief in the project rather than fully fused. I will try again with a temp around 1150 degrees.

[Morganica]

SEGMENT Rate Temp Hold
1. HEATING 1 300 1150 35
2. HEATING ll 200 1370 30
3. Heat to Forming Stage 400 1470 15
4. Anneal 1: 9999 950 60
5. Anneal II: 150 800 10
6. Cool Down 300 100 0

Not quite clear on why you need three segments/holds to get to your top temperature, but more than likely if you check the kiln after segment 2 you'll be much closer to a "contour" fuse (new term for me, too). I tackfuse (i.e., fuse so that the pieces retain all/most/some of their shape in the final piece) at somewhere between 1325 and 1390 most of the time in my main kiln. Your mileage may vary.

One thing, though: How much contour are you looking for? If the pieces retain their shape so that they soften but look more glued together than fused, you'll need to revisit your annealing schedule. The more distinct the components, the longer the anneal required.

[Anne Marie Flaherty]

Thank you Cynthia,

I just followed what S76 suggested and it worked the first time. Contour is between a tack and a full fuse. When you say visit your annealing process what part do you think I should adjust? I'm new at all this, I just understand why it changed from cycle to cycle?
Thanks

Anne Marie

[JestersBaubles]

1470 is not s96's contour fuse. That's a full fuse. check your info again.

Dana

[Morganica]

Thank you Cynthia,

I just followed what S76 suggested and it worked the first time. Contour is between a tack and a full fuse. When you say visit your annealing process what part do you think I should adjust? I'm new at all this, I just understand why it changed from cycle to cycle?
Thanks

Anne Marie

I'm a little confused--who is S76?

If you're talking about pieces that mostly have melted into the base glass and are only very slightly raised above the surface with a total height of no more than 8mm, you're probably OK with the annealing schedule you have. I tend to call those fuses, because a lot of them have some small degree of "contour." If I'm referring to something that's absolutely flat across the top surface I'll call it a full, flat fuse. Semantics, though.

If there's an obvious joint between two components, you need more annealing time. Glass shrinks and contracts a bit as it cools, and if the components are distinct enough, they'll try to shrink away from each other. That causes stress in the glass which can lead to cracking. You slow down annealing so that the components have time to settle against each other without inducing stress.

On the change in results from cycle to cycle, not entirely sure. Sometimes it's as simple as the colors of glass you're using. Black, for example, is a very "soft" glass, meaning that it moves and gets gooey at relatively low temperatures compared to, say, white glass. If your initial projects were done with harder glasses, switching to soft glasses would definitely give you a different surface.

It could also be that your kiln is having issues. Hard to tell.

[Judd]

Anne Marie,
(My daughter is Ana Marie - nice name.)
S76 - what is that? Are you talking about a glass with a COE of 76, like float/ window glass? Even if you are, the 1300s should be enough for warping, tack fusing, etc. for float glass, and getting close to a full fuse for 90 or 96 COE glass.
Good luck.

[linn keller]

anne marie,
by any chance do you mean s96 for spectrum 96? i'm thinking that since you mention an anneal of 950 and that it's from their website, that's what you mean.
in my kiln, that 30 min. hold at 1370 has the glass softening and going to 1470 at only 400/hr would mean a lot of headwork on the glass and flat as a pancake after 15 or 20 min. at 1470. since processing glass to any stage is a blend of time AND heat, if you take a long time to get to a fusing (or contour or any other stage), it should take less time at your peak temp or maybe be "done" without having to go that high.
bullseye glass has a great set of educational "technique" sheets that i think might give you some ideas about mixing heat and time. tech note #4 (i think) is glass and temp. if you go to their website you can read it and the others (free access) and even though the temps will be a little dif. with spectrum, the info is the same.
hope this helps
linn