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Author: Subject: Spontanious Cracking on New Branded Glassware ?
LuckyWinner
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[*] posted on 6-8-2020 at 01:47
Spontanious Cracking on New Branded Glassware ?


I was simply distilling water with my new 250ml RBF from DURAN.
it was expensive and was not used before.

it was placed inside an aluminium heating block with PTFE stirrbar
on a hotplate, wrapped in several layers of aluminum foil.

heated to 200C then dropped down to 120C to get around 1 drop of distilled water every 6 seconds.

after ~25 min i heard water violently evaporating.
hotplate got turned off immediately.

the DURAN 'made in germany' flask had long hairline cracks at the bottom,
which caused the water to leak out.


-how can this be?
-imagine this would have been diethyl ether... I guess my DIY fumehood would be blown up by now?
-I searched but could not find data about this exactly.

-should you always distill water and also perform a vacuum distillation
to check if your glassware does not have any tiny cracks , that may be the cause for this?

-how to make sure your new, branded glassware does not crack?

-never fully crank up your hotplate to 380C immediately for distillations?

-always gently slide in your stirbar, never drop it directly from the neck?

[Edited on 6-8-2020 by LuckyWinner]
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B(a)P
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[*] posted on 6-8-2020 at 01:59


There is nothing wrong with your set up. You should contact the supplier for a refund.
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wg48temp9
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[*] posted on 6-8-2020 at 02:07


Maximum thermal shock resistance is 160°C. Borosilicate glass can easily handle most lab temperatures, and can handle 400°C for short-term service, typically 200-230°C for normal, standard use service. Note that "short-term" in this case means "minutes", not hours

Ref: www.aceglass.com › dpro › kb_article




i am wg48 but not on my usual pc hence the temp handle.

Thank goodness for Fleming and the fungi.
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LuckyWinner
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[*] posted on 6-8-2020 at 02:07


Quote: Originally posted by B(a)P  
There is nothing wrong with your set up. You should contact the supplier for a refund.


the supplier was indeed questionable... just picked him cause he was closeby
and I could pay in cash and pick it up.
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Belowzero
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[*] posted on 6-8-2020 at 02:25


I had this happen recently with a nearly new 2L scott duran beaker, supposedly the best glassware around.
A small crack , then 1.5L of hot solution all over the place.
Don't want to imagine if it was anything actually dangerous, just a real big mess and a lot of cleaning up :S
Reminded me to always expect the worst.

Shit happend I suppose, micro cracks , maybe during shipping , who knows.




[Edited on 6-8-2020 by Belowzero]
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LuckyWinner
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[*] posted on 6-8-2020 at 02:28


Quote: Originally posted by wg48temp9  
Maximum thermal shock resistance is 160°C. Borosilicate glass can easily handle most lab temperatures, and can handle 400°C for short-term service, typically 200-230°C for normal, standard use service. Note that "short-term" in this case means "minutes", not hours

Ref: www.aceglass.com › dpro › kb_article


thermal shock means a quick temperature change of 160C ?
that means a Borosilicate glass with boiling water can be dropped inside an ice bucket
asap without it cracking?

the normal service temperature for Borosilicate glass is 200-230°C , that means you should never crank up your hotplate over 230C ?

for example when distilling a liquid its best to set it at 200C max or should you always slowly gradually heat it up in 50C units till your BP is reached?
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LuckyWinner
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[*] posted on 6-8-2020 at 02:35


Quote: Originally posted by Belowzero  
I had this happen recently with a nearly new 2L scott duran beaker, supposedly the best glassware around.
A small crack , then 1.5L of hot solution all over the place.
Don't want to imagine if it was anything actually dangerous, just a real big mess and a lot of cleaning up :S
Reminded me to always expect the worst.

Shit happend I suppose, micro cracks , maybe during shipping , who knows.




[Edited on 6-8-2020 by Belowzero]



there are anodized aluminium trays for baking.
its basically the same material as lab heating blocks.

would you think this could be a 'safety wall' in between your flask and hotplate?
in case the flask cracks your liquid will be spilled and contained inside the baking tray.

the tray will still be hot and may cause explosions.... but I guess its better
then soaking your hotplate and fumehood with the reaction materials.

seems to be an alternative for reactions that do not use a heating block
since...
... if you already use a aluminium heating block and fill your flask max 1/2 full
your heating block should contain the liquids.
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LuckyWinner
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[*] posted on 9-8-2020 at 00:38


need to update cause I guess it was my fault cause I heated the hotplate to 360C for a long time
to get the temp up.

that was too much thermal stress on the flask which caused it to break.


lesson do not crank up the hotplate to max temp, gently heat your flasks.
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