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Author: Subject: Repairing cracked glassware
ave369
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[*] posted on 26-9-2015 at 07:05
Repairing cracked glassware


Today I've got a big problem: my favourite retort developed a small, web-shaped crack in the side. It's not yet severe enough to let water through, but if I leave it alone, it will become that severe.

How to I patch up the retort? Don't want to buy a new one, this needs a trek to Moscow, which is several times more expensive than the retort. Will a krazy glue patch do?




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Pyro
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[*] posted on 26-9-2015 at 12:59


try visiting a glassblower. I did that with a cracked pressure equalizing funnel and he fixed it up in 2 minutes.




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[*] posted on 26-9-2015 at 13:11


Heat ! Heat !

Pyro is right : it needs somebody who understands how glass works.




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[*] posted on 26-9-2015 at 13:40


Depends on the piece. Major repairs may require annealing in a furnace. A star crack might only require heating the area with an Oxypropane torch, until it fuses.

Glassblowers may have become a rare breed. Dunno. Plenty of Bong Makers around though.

Bong Makers have more-or-less the right equipment.

https://www.youtube.com/results?search_query=scientific+glas...

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[*] posted on 26-9-2015 at 14:08


Good glassblower. The one I used said he couldn't anneal a star crack in vacuum flask. Probably doesn't like to do simple stuff. I had another glassblower who repaired a crack in my 22L flask. I no longer need such a large piece and I sold it too cheaply along with the heating mantle.



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[*] posted on 26-9-2015 at 16:14


You can pick up a handheld butane torch for pretty cheap. That should be hot enough to melt a small area of glass to allow it to fuse back together.
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[*] posted on 26-9-2015 at 17:56


Quote: Originally posted by Upsilon  
You can pick up a handheld butane torch for pretty cheap. That should be hot enough to melt a small area of glass to allow it to fuse back together.


Without a proper oven to anneal the glass in the retort will be very fragile.




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[*] posted on 26-9-2015 at 18:03


Ave knows about thermal expansion. A retort might not be fixed by local melting, without annealing, in terms of its function, as might flask. So if the question is annealing, in the glassblowing book in the sciencemadness library, I remember one may gradually heat all over with propane torch to build up a layer of soot. But that is likely to be unhelpful, it is only for general interest and to advertise the book.

You live in some woods in Russia? An insulated enclosure might be helpful, you have wood or charcoal, I just don't want advise you to ruin it beyond any repair. Russian intuition is supposed to be powerful.




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ave369
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[*] posted on 26-9-2015 at 23:33


Russian brick oven is also very powerful. It's a workable low-tech replacement for an annealing furnace. Normally I use it for baking pies, but with double or triple load of firewood, it will work as an annealing furnace. I also have a propane-butane torch, it's what I use instead of a Bunsen burner.

But I've found a riskless method: covering the retort with a layer of cement (BaSO4 + MgO + waterglass + finely ground rockwool). Right now I'm trying to choose: use the riskless method, enclosing the retort in a ring of cement, or risk using the burner and oven.

UPD: tried to weld the cracks. Maybe the burner is too weak, maybe the glass is of wrong type, but, although the cracked side dented a bit under the flame, the cracks show no signs of shrinkage, I think, they even enlarged. No, I'm going to use cement.

[Edited on 27-9-2015 by ave369]




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ave369
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[*] posted on 27-9-2015 at 11:30


Addendum 2: on the Russian chemical forum, people advice me to treat the crack tips with HYDROFLUORIC ACID. This, as they claim, will stop the crack propagation on heating by preferential dissolving of the strained glass.

Naturally, I'm frackin' afraid of HYDROFLUORIC ACID. What do you think? Will it work? And should I stock up on lead, copper and gas masks to make The Demon?

(I have some fluoride in stock, waiting until it's absolutely needed. So I can make The Demon if I want to. But do I want to?)

[Edited on 27-9-2015 by ave369]




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[*] posted on 27-9-2015 at 11:52


It would be safer/quicker/more effective to get new glass than to make HF to repair it.



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[*] posted on 29-9-2015 at 16:11


New stuff might be difficult to obtain in Russia. Me, I'm in the US. Supplies are cheap and plentiful via e-bay, etc.. I send the supplier a little money, and a few days later, my stuff arrives, even when it comes all the way from China.
Guys in Europe seem to pay twice as much.

I'm generally a little surprised by the scientific obstacles faced by chemists in other parts of the world. Prices are usually high, and many restrictions on availablility may exist.

A nearby, trustworthy glassblower, would be a blessing. Oxy-propane or Compressed air+propane yields a much hotter flame than propane alone, and such combinations are utilized by the local bong makers and jewelers. A regular Oxyacetylene rig, with propane, and a propane tip, will do the job nicely.

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ave369
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[*] posted on 30-9-2015 at 13:04


Common new stuff is readily available by mail order. This way I can obtain test tubes, flasks and beakers, and many of the safer chemicals, up the wazoo. But a retort... Moscow is the only place where it can be bought, it is technically possible to order it to be delivered to another town, but extremely inconvenient.

As for glassblowers... Technically I can try to look for one in the regional center. But it'll be very hard, since they usually do not advertise themselves in easily available media. The town where I live is very small, economically depressed and lost in the forests, there is exactly one hireable craftsman who welds metal, and none who can weld glass. I think he has a propane adapter for his oxyacetylene rig, but I think he will be surprised when he sees the retort. Surprised and suspicious. I don't want any rumors about secret meth labs in my house.

I think the best decision for now is patching up the retort with a layer of cement, temporarily. And then waiting for the next occasion to visit Moscow.


[Edited on 30-9-2015 by ave369]




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