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guy
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Beakers cracking
I have had my beakers for about a year now. They have been used for heating a lot during that time. Now my beakers are slowing cracking AT ROOM
TEMPERATURE. Is this normal?
edit: i got it from UGT
[Edited on 5/16/2007 by guy]
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Ozone
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Are you sure that no one else was fooling with your glass?
I've never had glassware spontaneously self-destruct under ambient conditions...Unless...there was a polymer coating added by me which contracted on
cooling straining the glass. I suppose that fluctuations in the ambient temperature could be the "straw that broke the camel's back"?
That one's a bitch. I'd check for "gremlins".
Cheers,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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guy
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Before that I had been heating it on an open flame. But it cracked looong after if it had cooled. I think I heated it yesterday. As I was scraping
off the crystals it cracked.
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The_Davster
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Another vote for Gremlins
I prefer open flame, as my heating equipment either stinks(hotplate), or I do not trust that it is not full of asbestos, so I am very friendly with my
alcohol burner. Never had an incident with a crack despite using naked flame on aqueous solutions in UGT flasks for hours at a time. Thats gotta be
a steep gradient.
[Edited on 16-5-2007 by The_Davster]
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UnintentionalChaos
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Rack up another tally for gremlins. The only glassware I've ever cracked (other than dropping it, which is a sadly common occurence....stir-rods don't
have a fighting chance) was several hundred grams of KNO3 and about 200ml of water in a cheapo beaker over a gas stove. The temperature gradient was
so steep that there were pockets of molten KNO3 at the bottom shielded from the water by their temperature which was boiling off all the water that
tried to seep down. This was a while back and I wasn't paying attention to the beaker until it was too late. A large segment of the beaker slowly
cracked out around the largest pocket of molten KNO3, but I was fast enough to save all the contents. I still have the beaker. Except for an oval
chunk missing, its structurally sound. I use it for gravity filtration of nontoxic, flushable stuff into the sink. No need to worry about the liquid
level hitting the bottom of the funnel since it all flows out and down the drain.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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leu
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Borosilicate glass will crack at ambient temperatures for many reasons, one of which is that using an open flame heats part of the glass to the
annealing point thus inducing stresses within the glass which cause fracture upon cooling  Even if the glass is heated with more gentle methods such as an infra red lamp, a draft of cold air can fracture the glass for similar
reasons when it's cooled to room temperature  One can expect a certain amount
of glass breakage during laboratory work, it's to be expected 
Chemistry is our Covalent Bond
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evil_lurker
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Might be a good time to stick the rest of your glassware in a self cleaning oven and run it thru a cycle and wait till its completely cooled before
taking it out.... hopefully that should re-anneal it.
Not all chemicals are bad. Without chemicals such as hydrogen and oxygen, for example, there would be no way to make water, a vital ingredient in
beer.
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Pyridinium
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When I stopped heating glassware with a naked flame, I stopped having problems with cracking 
A small focus of heat on the glass sets up stresses that can persist after the heat is removed. Of course you could alleviate this problem by having
an annealing oven and re-annealing your glass after use 
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Ozone
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I am curious, guy, what brand of glass are you using?
Cheers,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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MadHatter
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Bomex
That's the only type of glass that's cracked on me for any heat-related reason. I can't
say that about Pyrex/Kimax/Simax/Schott-Duran.
From opening of NCIS New Orleans - It goes a BOOM ! BOOM ! BOOM ! MUHAHAHAHAHAHAHA !
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Ozone
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That's where I was going.
Bomex is the plaything of the gremlins! (I have had the bottom just *fall* out with this stuff)
I have never had this happen with any of the brands you have cited (I don't know about Simax), MadHatter, unless there was an external stress
applied--A heavy buchner on a relatively thin-walled vacuum flask (which is a major boo-boo when hot and under vacuum), for example.
Schott-Duran is the "shit",
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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evil_lurker
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Hahah, mason jars have more resistance to thermal stress than Bomex!
Not all chemicals are bad. Without chemicals such as hydrogen and oxygen, for example, there would be no way to make water, a vital ingredient in
beer.
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guy
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What's the type of glass they sell at UGT?
And what is the "gremlin" joke here?
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evil_lurker
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UGT sells pyrex equivalent glassware (some is actually made from pyrex glass).
Gremlins are small mischevious fictional creatures aviation personel assigned blame for unexplained and/or unexpected mechanical failures of aircraft.
[Edited on 17-5-2007 by evil_lurker]
Not all chemicals are bad. Without chemicals such as hydrogen and oxygen, for example, there would be no way to make water, a vital ingredient in
beer.
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Magpie
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I have Kontes RBFs and Pyrex/Kimax beakers and Erlenmeyer flasks. I have only lost one piece to cracking. This was a 1000 mL Pyrex beaker in which I
was evaporating a calcium acetate slurry on a stirrer-hotplate. I wasn't watching it closely enough and it got too dry. I blame myself, not the
glass.
[Edited on by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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guy
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So no heating on open flames?
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Pyridinium
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| Quote: | Originally posted by guy
So no heating on open flames? |
Correct. It's one of those things you "might" get away with, might not. Why chance it? While others have had good luck with Kimax and Pyrex, I've
managed to break these using naked flames.
I use Bomex all the time. Just use wire gauze or some other way to diffuse the flame. Better yet heat with a water bath or heating mantle.
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undead_alchemist
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For those of you who don't know, Bomex is owned by Kimble. So at the same time, you don't know if your Kimax brand glass is coming from Kimble's US
plants, or from the Kimble-Bomex plant in China.
http://gerresheimer.com/index.php?id=194&L=1
http://gerresheimer.com/index.php?id=193&L=1
[Edited on 19-5-2007 by undead_alchemist]
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DerAlte
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Have never had such a problem, but I always use a sandbath for temps >100 C and a water bath for those below. A water bath even works with
commercial glass jars provided there is no temp shock. I also use Corelle by Corning for evaporations, although I have a nice porcelain dish. It is
basically a glass, I beleive. Great stuff. Even looks professional if undecorated.
All glasses have internal strain. If you scratch it you provide a stress relief line and it cracks there preferentially as all glaziers and glass
blowers know. Perhaps you had a scratch.
I have destroyed many flint glass test tubes but only one borosilicate (Kimex, Pyrex) and that was due to drying a powder with liquid on top. A red
hot tube can't stand being suddenly cooled!
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chemkid
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I just recently cracked a 400mL bomex beaker on the stove heating sodium bicarbonate. I use my glassware a ton and sometimes i am working on rough
surfaces etc. so my glassware is taking a lot of wear and tear. Which would be more recomendable for a replacement - pyrex (another buck more
expensive) or bomex again?
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UnintentionalChaos
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Its all about luck. I'd splurge on the pyrex. They are generally much better made, have thicker walls, and fewer occurences of bubbles (if any). I've
trashed a few bomex items, but all of the pyrex and chemglass has given me no issues.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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guy
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So if I want to fuse something like sodium bisulfate, what should I use?
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Ozone
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It seems to me that crystallization or heating to dryness is key. Perhaps the crystallization leads to a contraction whilst intimately adhered to the
glass (which strains and can crack it, with least provocation)?
Either way, I have crystallized in Pyrex with no ill effects.
Cheers,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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chemkid
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Ok I will go with the pyrex
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prole
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Heating non-Pyrex glass
I purchased some 4L amber glass bottles for solvent storage, and they arrived smelling like an essential oil wharehouse, which is fitting because that
is where they came from. Soap and water, and acetone do not remove this smell. 10% ammonia does so very effectively. It takes several days for the
smell of ammonia to dissipate after an ammonia rinse, and of course I need it clean and dry before then. The reference from which I got the ammonia
idea says to bake in an oven after rinsing, and they are for sure talking about Pyrex and other heat tolerant glasses. My bottle is not Pyrex. So my
question is this: can I drive off the smell of ammonia in an oven at 150F without cracking my bottle? I am guessing it will crack ( I see a few
bubbles in the glass), but if slowly heated and slowly cooled, would it possibly remain intact?
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