Lampwork Etc.

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-   -   Can Glass be Re-Worked after being Annealed? (http://www.lampworketc.com/forums/showthread.php?t=312269)

stafford.glassworks 2019-09-29 8:09am

Can Glass be Re-Worked after being Annealed?
 
I have a little pendant that I finished 2 days ago which I annealed but I forgot to melt the punty marks off I was just so ready to get it in the kiln before it cracked. Hopefully I don't ruin it by donig this but I've put it in the kiln to wam up and am going to attempt to just melt a little bit of the punty off that's stuck to the bottom from where I broke it off. I'll let you know how it goes but I haven't read anywhere about re-melting glass after it's already been annealed. It'll be interesting to see how it turns out. I tried to do this on another one but i made the rookie mistake of trying to remelt it when it was cold and it cracked. Hopefully this will make a difference.

playingwithfirebeads 2019-09-29 9:51am

With boro - yes as long as its heated in kiln first.

Alaska 2019-10-09 3:44pm

Agree with the post.

With boro, place the piece in a cold kiln and ramp up to your annealing temperature. Remove and in some cases it may be necessary to slowly bring the piece back to working temperature in the flame.

Use this technique and it has worked every time.

When finished, place back into the hot kiln and anneal, etc.

menty666 2019-11-03 5:51pm

If you happen to have a Little Torch, there's a third party, extra long tip you can buy for it for doing in-kiln repairs. Good for when you need to hit one tiny spot and that's it.

Nighthawk 2020-10-28 4:27pm

Heat first or tiny air bubbles will expand and ruin your day :)

indigolove11 2021-12-15 6:12am

My question is at what rate should I heat up a Boro pendant in the kiln before I attempt to fix it on the torch? Does it have to be a slow process up to 1050 or so or can I ramp up full speed without it exploding inside my kiln?? Anyone have any suggestions or experience “fixing” a Boro piece this way?? Thanks in advance—

rcktscientist 2021-12-15 8:17am

The warm up cycle should be the exact reverse of your annealing cycle.
So, fast ramp up to around 950, maybe 920 to be safe (950 is strain point of boro)
Then, slow ramp up to 1050 (through the annealing range)
Finally, pull out of kiln and warm up in a bushy, cool flame until glowing.
After that, treat it as a freshly made pendant and modify to your heart's content followed by proper annealing.

I just did this last night with a 1.5" diameter round pendant, about 1/2" thick.
Never had an issue with this approach since it's science-based. Bandhu Dunham has a great section on annealing in one of his books. Helps to fully understand what the glass is experiencing.

Good luck!

indigolove11 2021-12-16 7:28am

What would you determine was a slow ramp up?
 
Ok that’s good to know and I kinda had figured as much I just didn’t wanna try and completely ruin what I want so badly to fix. My last question is how slowly should I ramp up from 920 to 1050 like at what rate degrees per hour? Really slow like 100/hr or like 500/hr or some other amount? And I don’t typically anneal things for long I guess I don’t honestly know how long is or would be proper? I know it depends on the piece and thickness I’m sure— I’m just doing marbles and pendants at this point and not super large ones necessarily… though I do make marbles about an inch n half and even those I rarely leave them in the kiln at 1050 for more than an hour usually 45 min and then I just click the kiln off and let it cool at its own rate and I don’t mess with checking it by opening the kiln at all for a good 8 hours usually…is this enough time? I can’t say that I’ve experienced any cracked or necessarily weak pieces at all yet so maybe this is right?? I’m just rolling with what feels right at this point …. Instinctive lampworking you might say — 😂 but am always in search of advice or any tips or tricks anyone uses…. Thanks in advance!!

rcktscientist 2021-12-16 8:46am

I think a safe bet is a rate that is slow enough for the slow ramps which would be good for the fast ramps too. Did a quick check of the Dunham info and found some good data for you: (glass type and thickness, fast heat rate, soak time, slow cool rate)
0.5" marble, 107 f/min, 15 min, 18 f/min
1.0" marble, 26 f/min, 15 min, 4 f/min
1.5" marble, 11 f/min, 34 min, 2 f/min
0.5" pendant (laying on it's back on kiln floor) - treat like a 1.0" marble
*Looks like he doesn't do a slow ramp up, but I do it because of my quirky kiln.

Remember, internal stress caused by improper annealing may not show itself for some time or until some mild shock is introduced. I've heard several stories of glass pieces cracking months after being made.

Hope it helps

bigdumbslabz 2021-12-28 5:36pm

im working with no kiln due to no electric ran yet but i made a spoon and reheated after it cooled to add a horn i made it work

LarryC 2021-12-29 9:45am

Quote:

Originally Posted by bigdumbslabz (Post 5121651)
im working with no kiln due to no electric ran yet but i made a spoon and reheated after it cooled to add a horn i made it work

Doesnt mean its a good workflow to use. Glass is a cruel master and it will bite you at the worst time unless you understand its working properties and make good judgements based on them.

phentron 2022-01-18 4:33am

I have re-heated & worked boro objects up to 12mm (1/2") thick without first using a kiln. Start with a cold flame (low oxygen) and hold the object far out in the flame (past the visible flame) - this may take several minutes. When you think it is evenly heated through its thickness, SLOWLY bring the object to the hot part of the flame. Now work the object normally.
If your object is 18mm (3/4") thick, it will take 5+ minutes to heat - if I had a kiln, I would use it.
Also, if the item is valuable and can not be replaced, I would use my kiln.

Peter


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