first break in a long time

[jkglassworks]

well, I've been fusing along for a while now, no problems, I was just about to say I think I might be getting the hang of this! BUT, alas, little cracks have infiltrated my latest piece

it is about 4" x 8". All BE glass.
I first fused the two base layers together.
I don't have that schedule in front of me, as I did in the kiln at my daughters school.

It came out fine. no cracks or breaks.
there were a few little air bubbles in there though. probably due to the layering of those two glasses, and the confetti and streamers being face down on top of the spring green.

Next I layered the design element on top and used this schedule:

300 300 10 min
300 1350 15 min
AFAP 900 1 hour
100 800 15 min
Off

when I took it out of the kiln I could swear that there were no cracks. I suppose I didn't look at it THAT closely, but I really don't remember seeing them.

Today I took it down off the windowsill where it was leaning for a day or so (could that have been when it happened?) and I noticed a few cracks:

this one runs across the back

and the stuff on the front is cracked as a result

and around the blue feet parts there are little cracks on either end.

So, do you think that there is an issue with too many colors? could it be the fault of air bubbles in the base layer? How would you change the firing schedule?

Thanks in advance for your help!
Joanne

[jkglassworks]

these are the little cracks around the feet

[Marty]

You're not annealing nearly long enough. Tack fusing is very demanding- you've got different thicknesses of glass that need to cool at the same rate and the easiest way to achieve that is to slow down. I know BE says to start at 900 but starting at 960 won't kill you. Take 4 or 5 hours to get to 700 and hold there for 30 to 60 minutes. Then turn the kiln off and don't peek or vent until you're close to room temp.
That beetle is cool- try it again (or heat it up gently and see if you can heal those cracks).

[Laurie Spray]

Way too fast. Personally I would anneal for 2 hours then 50/hr to 800, hold 60 and off. Such a fun piece too! I would refuse it although to heal the cracks you will lose the wonderful effect you got from the tac fuse.

[jkglassworks]

thanks for the help.
I will just keep this one for my own personal collection. But I plan to do two more, so your words of wisdom will help me out with those.
thanks again, I really appreciate the help I get here.
what would we do without the internet?
Joanne

[Morganica]

Rule of thumb: Take the maximum thickness of the piece, multiply it by 2 or 3. (For example if you've got three layers with your beetle, 9mm X 2=18mm, 9mm x 3=27mm) Look up the annealing schedule for that thickness, and follow it.

Whether you use 2 or 3 depends on how distinct the decoration is from the base, and how sharp the join angles--the more distinct and sharply angled, the higher the multiplication factor. You've got separate pieces of glass insulating the base, cooling and contracting away from each other, and that adds stress to the piece.

[Vonon]

What a great bug! Love it. Is your signature fired on?

[jkglassworks]

why yes it is!
I do stained glass as well, and I have started to fire it onto a piece when doing a larger panel as well. the most permanent way to sign glass!

[jkglassworks]

back to the beetles...if you will humor me for a minute more

I made two more (the lfet and middle) the right is the original broken one.

Using the previous suggestions, I plan to tack fuse the left two with a schedule of:
300 300 10min
300 1350 1 hour
AFAP 960 2 hours
50 700 1 hour

Do you think there would be any difference in the behavior of the iridescent piece and the green one? Should I not do them together?

Thanks!

[Laurie Spray]

hold at 300 does nothing
I personally would not hold at 1350 because it is in the devit range…..but I guess it worked for you last time?
is the base glass already fused as I see no bubble squeeze?

[jkglassworks]

yes, the base is already fused.
so I will get rid of the 300 hold.
looking at my previous schedule, I only held at 1350 for 15 minutes. Good thing I checked!

Since I am not doing a bubble squeeze can I just go straight to 1350? Should I hold it at all? stick with the 15 minutes?? I did not have any devit on my original piece. just the cracks (and btw, it is now completely broken in two)

Even though I have been fusing for a while I am still not confident in my scheduling capabilities, so I thank you all for your help! and hope to someday be able to dispense help too

[Laurie Spray]

I would not hold more at 1350 than you have to…..

[jkglassworks]

ok. I am going with this
300 1350 10
afap 960 2 hours
50 700 1 hour

and I am only doing the middle iridescent base one. I need to full fuse a body part on the other one first....

[Stephen Richard]

What is th soak at 371C going to do?
In my view - nothing. It is below the strain point, so no further annealing can be done. The aim to me is to steadily cool the glass to room temperature. The. Soak does not do that.

[jkglassworks]

well, I am happy to report, that there were no issues with my schedule.
I actually turned the kiln off last night before I went to bed at the point when it was about 750 and let it come down naturally. The kiln is is the sunroom and when it is done it has 14 very loud beeps in a row which I thought would probably wake me up two hours later (wanted to avoid that!)

thanks for all the help. now to do the other two!

[DonMcClennen]

I disagree with your statement that there are no issues with your schedule...when cooling, AFAP to 960 is entering the top portion of the anneal zone too fast. AFAP to 1000F then 80 to 960 is a safer approach! This extra ramp may save you in the future.

[Laurie Spray]

I fire 9999 to anneal all the time and I never have issues…..I think it depends on your kiln and how fast it cools. mine is very insulated and cools slowly.

[Jerrwel]

Firing Schedules for Glass, Graham Stone's book available from Warmglass http://www.warmglass.org/books/books/126-fsg will help you create the right schedule for each project you create; no researching, no wondering, no worrying, no dithering. OK, maybe it's not a panacea but it's close.

Page 33, Uneven Heating and Thermal Mass, addresses the process issues you introduce in your beetles and suggests how to find the 'correct' schedule from the book. The 5/8-inch schedule is probably what I would use given all your different colors, shapes, and contact points. I've found recently that small contact points like the beetles' feet created my worst cracking situations so I'd be more cautious than even the 1/2-inch schedule. The schedule is estimated to take 18 hours; another great aspect of the book is the estimated time for each schedule.

How do we know a project is properly annealed and without hidden stress that may literally cause our work to explode in the future? We don't; therefore, we should be using a standard process be it manufacturers' schedules or Stone's book to assure ourselves (if not our clients) to as great a degree as possible that we are producing safe/stable products.

[jkglassworks]

thanks Jerry
that sounds like a book worth taking a look at!
Joanne

still no cracks.....