I received a couple of round bottom flasks from china and they have some warps and flat spots in them. I mentioned my concerns to the supplier and
they said to test them and they would replace them if they broke.
I have a pump and hotplate but don't really know how to test these without risking destroying equipment. Any suggestions?Sulaiman - 19-1-2019 at 08:45
Can you post one or more photographs ?XeonTheMGPony - 19-1-2019 at 08:56
to test:
Dry heat it, to 200c, allow to cool
Dry heat hot to touch, add room temp distilled water
Boil water then place in cool water bath (10c apx)
Dry heat again
If it survives that it should survive the bulk of lab use.Metacelsus - 19-1-2019 at 10:33
You might also want to test pulling a vacuum on them. If you have a polarizing filter you can also look for stress points within the glass.macckone - 19-1-2019 at 11:42
modification of xeon's tests.
Heat in oven to maximum temperature (most ovens this will be somewhere near or over 200c.)
Allow to cool to room temperature.
Place the flask in a pan of boiling water (borosilicate glass should withstand 160C temp change)
Allow the flask to sit in boiling water until it is hot then place in a mix of ice and water (0C).
Next pull a full vacuum on the flask.
The last dry heat is probably redundant.XeonTheMGPony - 19-1-2019 at 14:31
Why I do the final dry heat is one to dry it, but two is to show any fissures that may have formed, so for me it is the final pass n dry befor it goes
into the shelf itsafineday - 19-1-2019 at 16:23
Awesome replies! Thank you VERY much. This will be fun and if they survive I should have more confidence in them than if they were perfects. Really,
one just has a little divot but the other is 4 grams lighter and has a fairly large sag. The supplier is always super cool about issues but they
will certainly let me keep crap if I don't catch it.
I'm not a smartphone user so posting a pic means borrowing a camera. VSEPR_VOID - 19-1-2019 at 17:48
Wrap your hot plate's top in foil to keep it clean if something breaks. Also make sure to store your electronic equipment, such as hotplates, in a low
humidity environment and keep them clean. itsafineday - 20-1-2019 at 09:03
You might also want to test pulling a vacuum on them. If you have a polarizing filter you can also look for stress points within the glass.
Is a polarizing filter like a polarized lens ? What do the stress points look like?itsafineday - 20-1-2019 at 11:48
So one of the 500ml flasks went from 170c to 32 c and went crackle but didn't fall apart. The other 500ml handled 150 c to 32c without a problem.
The ball canning jar I threw into the mix because I just had to know and it cracked and fell apart when it went from 140 to 32c . All three were
able to take going from boiling water to ice water without issue. macckone - 26-1-2019 at 22:44
To achieve the full 160C, the glass has to be pretty close to perfect.
Boiling water to ice water is only 100C and usually more than sufficient for everyday lab work.
Ball canning jars are not designed to go from boiling to ice, I am really surprised that survived.
What did you use for 32C? are you sure you don't mean 0C (32F)?itsafineday - 27-1-2019 at 05:09
I was using an infrared thermometer . I did the boiling water to ice water test first. The ice water was left on the stove as the oven heated over
30 minutes so the ice in the water melted and apparently the water warmed a bit. I was pretty shocked about the mason jar , too. Ball mason jars
kick butt. The one flask actually survived the dry heat of 140c and the 32 c water quench. I don't know how accurate one of these thermometers is
for something like an empty rbf, though.
So , to be honest, I think I was a bit unfair in the test with the oven. I was glad that I was able to piggy back the rbf with another order to
minimize the suppliers loss.
