Ping

[Susan Moore]

Tack fused some Spectrum transparent - a 5 inch square of a bunch of bits 1/2 inch diameter and smaller, 2 - 3 layers thick - in a hotbox. I held the temp at 950 degrees and 750 degrees for 10 minutes each on the way down to anneal. Let it cool overnight and the next morning I'm walking by and hear a little "ping". Hmmmm...a few more little pings over the next couple minutes. No cracks or fractures.

I have fused the little bits with BE and no problem at all. Fuse, slump, no pings.

What's with the Spectrum ping thing?

Susan

[Jerry]

Susan,
I won't get into the Spectrum vs. Bullseye thing; we've been there too many times. About your project, if you believe it's coming apart because of cooling too fast, the easy answer is to cool more slowly! My rule is to anneal one hour for every 1/4" of glass. That's conservative, I know, but I don't ever hear a Ping.

One other point, since you raised the temperature question; the drop in temperature from annealing (960 for Spectrum) to 760 needs to be slow if you are working a large piece. Typically, for a combed platter with added rim and base sheet, I'll anneal at 960 for 3 hours and then drop from 960 to 700 at 75 degrees per hour. The theory is that annealing occurs somewhere in that range, and if you pass through it slowly enough, you'll be just fine.

Hope that helps
Jerry

[Tony Serviente]

Whenever I hear glass make noise on it's own, there has always been something to see. Either a crack in a flat piece, or a check in the folds of a slumped piece. Wondering if a crack may be masked by running along the edge of a colored piece.

[Susan Moore]

I think there must be a fracture somewhere and I just don't see it. I fused a similar piece a couple weeks ago and I know I took it out way too soon - still 500 degrees (I'm a newbie - I didn't know!) and I heard a bunch of pings - still didn't see any fractures. I refired and left if to cool down to room temp and it is fine now.

I normally just make jewelry and only Bullseye, but I had this Spectrum around and just wanted to make some small bowls so basically I followed the same MO as I do with BE.

Since I'm just using a hotbox it is tough to keep an exact temperature and that is probably my problem. I'm going to slump this piece and cool it slower as suggested.

Thx for your help.

Susan

[Tony Serviente]

If you slump it, and it does have a hidden fracture, it probably won't be hidden when you open the kiln. They have a tendency to run when you reheat. I've fused thick with both SP and BE and only time I have pings, is when annealing is insufficient or I've taken it out too hot. Good luck Susan.

[Susan Moore]

Oh I'm glad you told me that - I should maybe expect a split or two in my little bowl - it's cooking right now. Learning curve. Thx again.