Incredible shrinking dishes...?

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jennchem's picture
Incredible shrinking dishes...?

I'm not sure if this is the plaec to ask, but I'm having some trouble weighing some glassware. This glassware has been cleaned very well and kept in a dessicator. Whenever I weigh it on our analytical balance, the mass continues to decrease. The rate of this decrease slows after a few minutes, but the mass is still in a decreasing mode. Our balance is in good working order, and this problem is not experienced with anything else measured. We think the problem might be related to static or humidity or barometric pressure, though, we're not sure. Does anyone have any ideas? I would be very grateful.

Radish's picture
Static can definitely cause a

Static can definitely cause a gradually decreasing mass. Also objects which extend beyond the area of the pan can experience a "lift" if there is sufficient airflow underneath. Still, I am surprised that you would experience these problems with such a heavy object.

jennchem's picture
Thank you. That was helpful.

Thank you. That was helpful. The dishes I'm weighing are rather well curved glass bowls, so I will try weighing them upside down to avoid any problems with lift. Thanks again!

Fraser Moss
Fraser Moss's picture
To eliminate/reduce static

To eliminate/reduce static you can try a device like a ZeroStat 3 Antistatic gun

You click it a few times against object holding static before you use it.

I have used one to remove static from eppendorf tubes before I weight out small amounts of peptide. They work well.