Tuesday, July 19, 2011


Why does glass have to be so dang fragile?
The handle knocked against the side of the sink while I was washing it.

Is there any way to repair glass? (So that it's water tight, and won't explode?) Would heating it with a propane torch do it, or would that just cause it to explode? *sigh*

I loved that pitcher. It had a lip that didn't dribble, and was the perfect size for frozen juice.

Update: Hmmm found the following on a forum:
I have a slightly unorthodox one for you.

Get a blowtorch. Melt the glass at the crack. However, to avoid shattering it completely, you'll have to heat the entire thing up first - a LOT. Put it in a cold oven and load the oven up with bricks around it to hold heat. Bring the oven up to 500 degrees and keep it there for a good hour to ensure all the bricks are GOOD and HOT.

Then open the oven and, wearing 2 or 3 heavy mitts, grab the glass and using the blowtorch, melt the crack with high intense heat just on that spot. Work quickly so it doesn't cool down too fast.

Then put it back in the oven, leave the oven on 500 for another 20 minutes, then turn off the oven and LEAVE IT CLOSED overnight.

I have no idea at ALL if this will actually work - but from what I remember about glass blowing (my whole 4 hours of it), this might just do the trick. The blowtorch will work - it's the whole heating and cooling bit I'm worried about...

I have bricks and an oven, and I can borrow the blowtorch. (I think I'll leave it in the oven while I torch the side, though... as long as heating from only one side is fine. Of course, I'm not sure I'd be able to get the right angle inside anyway.) I'm not sure this is the right project for the heatwave though... perhaps I'll wait for a cooler day.

Comments? Suggestions? Warnings?


Nicoya said...

You work at a university. Go down to the chemistry department, find a glass blower and give it to them to fix.

noricum said...

You're up late!

Do you think the chemistry department does anything more complicated than bending glass tubes?

Rhiannon said...

I advise against this, however if you decide to try please get a mask or something to cover your face and wear lots of long layers to protect your skin. Burns from hot glass are no joke.

Sara said...

I have faith that you can manage it...just be careful!

Bethany said...

Based on my scanty knowledge of glassworking from a few lampwork bead classes, I'd be concerned. I mean, I know glass CAN be re-heated slowly to work again, but I also know that it has to be done carefully because it explodes very easily. I also know that the kilns used to heat/cool glass get much hotter than 500 degrees. (I think the one we were using last night was around the 900 degree range, and that was as it was in the cool-down phase.)

There's also the fact that the part you melt with the propane will be much, MUCH hotter than 500 degrees, and glass doesn't like it when two parts of the glass are at different temperatures. Unhappy glass usually means exploding glass.

I'll try to remember to ask the instructor at my class tonight, but unless you've read testimonials from people who have done this successfully I'd strongly advice against it. If it were just risking the complete loss of the pitcher it would be one thing, but this sounds like a good way to have 500 degree glass shards flying all over your apartment and into your face.

Note that even if it doesn't explode at the time you repair it, if the pitcher heats or cools too fast or unevenly it could also break unexpectedly at a later date, like while you're holding it putting water in it.

How about looking for a food-safe glue? Brief Googling suggests that Gorilla Glue may be food-safe when cured.

Bethany said...

For example: the instructor told us that if you run out of propane while you're working on a bead, if you don't have a kiln or another torch already lit to move it directly to, you need to give up on it and start a new bead.

I decided to try it anyway, of course. As soon as the half-done bead was no longer molten I stuck it in the vermiculite that insulates it and keeps it from cooling too fast. I got a new cylinder, set it up, and started re-heating the bead... and the parts for the bead that didn't shatter then, shattered later when I took the remains off the mandrel.

Just really likes exploding, glass does.

noricum said...

I kind of suspect the reason I keep breaking pitchers is that they haven't been properly tempered. I break *so* many of them. :P I wish I had a way to temper them.

I will definitely do more googling before trying to burn myself. ;) Perhaps I'll also e-mail my glass-blowing friend. (Sadly, he lives in Boston, so I can't just get him to do it for me.)

Bethany said...

So I asked my instructor about this tonight and her response was, "It would be a miracle if that ended well." (She also had a distinctly alarmed expression when I described the plan.)

Besides the fact that you'd need to get the glass much hotter than an oven can go to keep it from exploding when it was heated with the propane (closer to 1000 degrees than to 500) she pointed out that when heating cool glass, you always heat it very, VERY slowly -- over the course of hours, much slower than a home oven heats.

So the plus side, it will probably explode in the oven before it gets a chance to explode in your face. :-)

Seriously, though, I think the only way this would work would be if you had a proper kiln to heat it in, and if you knew what kind of glass it was so you'd know how hot it needed to be and how long it needed to take to get there.

I understand the DIY impulse but like I said on my FB... usually when someone tells me not to do something I joke, "Or what? It explodes?" But the joke doesn't work with molten glass because that probably IS exactly what happens.

So I really very strongly urge you not to try it. I don't think it's safe, and it's almost certainly going to end with the destruction of the pitcher. I'm sure you can find a food-safe epoxy to seal it up with that won't risk a 500 degree glass pitcher exploding in your face!

noricum said...

*sigh* okay mom. ;) Thanks for asking your instructor! (I was planning on inching the temperature up slower, but since it won't get hot enough anyway, scratch that.)

You don't think the crack will spread even if it is epoxied?

Bethany said...

Sorry. :-) I think would be a really risky thing to do, though.

Hmm, I hadn't thought about the crack spreading if you glued it. I'm not sure. On the other hand, at least it wouldn't be exploded...

noricum said...

A floor full of cranberry juice would rank above a face full of hot glass, but not by a lot. ;)