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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.
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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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[*] 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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Fyndium
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[*] posted on 12-1-2021 at 13:33


How prone is boro to break by water?

I use hot water bath at 90c to run a reaction, after I pump out the water and replace it to cool rxn to rt. Im afraid to use very cold water in fear of cracking my vessel. Tap goes down to 10c. Is this too much?
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[*] posted on 13-1-2021 at 02:55


DURAN is not a company, it is a glass type. The name of the company is "DWK Life Science". Also companies like Lenz, Witeg, Rottberg use DURAN type of glass and it is supposed that DWK Life Science makes supervision how DURAN brand is used. He does it with some success. I believe that Witeg is very good brand also (on its own).
"Schott DURAN" is a label usually I associate with an old glassware. If the supplier is not reliable that flasks with this marking could be even second-hand. Not sure about this but pretty sure that new flasks have "DWK Life Science" logo (or Witeg/Lenz/Rottberg which is the same quality range).

I think that 360C aluminium outside and cold water inside is too much. I use heatgun but the air stream is a different story. I raise the temperature of an air stream up to (internal + ~200C).

I use a lot of DURAN glass in my homelab, mostly second-hand but there are some quite new flasks. Most faults I've got due to mechanical stress (over clamping, dropping something inside - especially with beakers and test tubes). I've got only 2 thermal shock cracks - 1st when I put a beaker directly on a gas flame and second, when I tried to unfreeze a tap of a separatory funnel with a hot air (but in the second case it was not from DURAN glass, just produced by Lenz).
Considering the price of a new DURAN flask I would recommend to buy a second-hand DURAN or even Simax flask and second-hand heating mantle (with a good thermal control) as a more reliable combo.

Udate: some of genuine DURAN glassware is batch-numbered and has a quality certificate which you can download entering the "retrace code number" which is written on your flask. That way you can find the date of manufacturing and see that some tests where actually performed by the manufacturer.


[Edited on 13-1-2021 by teodor]
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[*] posted on 13-1-2021 at 06:21


I always do a mini "annealing" process for my own piece of mind when I get new glassware. Typically I'll stick new glassware that will be exposed to high temperatures in an oven or furnace overnight at 250-300 degrees Centigrade then in the morning allow to cool to RT. I know the temps aren't high enough to actually anneal the glass, but it makes me feel better about using the glassware.
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[*] posted on 13-1-2021 at 07:06


Quote: Originally posted by LuckyWinner  
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?


I've seen a paper where they tested this back in the 1940s for a number of borosilicate brands.

They heated the flask full of oil to a set temperature and plunged it into cold water.

All the major brands they tested withstood 160C and most had good safety margin but this was variable.

They authors also claimed a consistent additional resistance for flasks in absolutely pristine condition.
They said that a flask subjected to ordinary prudent handling will be appreciably less resistant to thermal shock than one which has been treated with exceptional care to avoid ANY impacts of even the most minor nature.
They hypothesized that tiny, even microscopic surface defects make the glass more vulnerable.

I believe the difference in shock resistance was some 40-50 degrees.

If this is in fact accurate then there might be some benefit to reserving a few specific flasks for high thermal stress situations and treating them with extreme care and using them only when they're really needed.

I have little experience with heating blocks, but I know that Optitherm metal liners aren't rated for very high temperatures.

I suspect that when they get too hot the expansion of the metal makes for a poorer fit to the flask and the heat transfer characteristics may suffer more than you'd think, at least with a round flask.

Hard surfaced mantles like Thermowell mantles have worked well for me, but these have a non-,metallic inner surface which probably doesn't expand as much at high temperatures.






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[*] posted on 13-1-2021 at 13:05


10C to 90C is 80C temp change.

That should be fine for 3.3 or lower expansion glass.

Good glass should go from boiling water to ice water without cracking.
That is 60C less than the thermal shock resistance value.

Keeping in mind that a condenser normally has cold water running through it and is often used with stuff above the boiling point of water.
Xylene comes to mind.
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[*] posted on 13-1-2021 at 14:55


I have heard the 160C limit more than once. I try to avoid any shocks whatsoever, and in this instance I slowly introduce the cold water, and the temperature difference slowly closes in, and the actual bath temp rises quickly to adapt the hot flask. This makes process straightforward as I can have the permanent installation of the 3neck flask with stirrers, condensers and other equipment installed, and I just adjust the height of the bath with jack and pump stuff in and out of bath and flask. Last time I suctioned the lower layer directly into a sep funnel and then removed the upper layer into another flask directly with gas washer, tubing and hand pump.
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[*] posted on 14-1-2021 at 04:39


Maybe a mixture of micro cracks and thermal shock?
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