[3dem] glow discharge "fireball"

[Debakshi Mullick]

Hello Jason,

We have seen this on our Emitech glow-discharge and were baffled. Also, our
grids looked kind of 'fried'. I say 'kind of' because we could not see the
carbon support film being obliterated every time, but, only on a few
occasions. In order to avoid it, we placed an insulator below this
grid-holder (either a silicone pad or a glass slide covered with Parafilm.
That took care of the pretty-pink fireball and all grids survived!

I hope that helps.

Cheers,
Debakshi

-Dr. Debakshi Mullick
Senior Cryo-EM Support Scientist
464 Bearsden Rd,
Glasgow G61 1QH




On Wed, 4 Feb 2026, 21:20 Jason Kaelber via 3dem, <3dem at ncmir.ucsd.edu>
wrote:

> Dear 3DEM,
> When glow discharging with our Pelco easiGlow (e.g. at 15 mA, 0.39 mBar
> room air for 25 seconds) on the aircraft aluminum grid blocks, sometimes a
> ball of plasma will be observed above one grid, or one ball each among
> several randomly-placed grids in the block. The ball is light pink and may
> manifest at any time during the discharge, typically enduring until the end
> of the cycle but perhaps flickering in and out of existence. Below I
> enclose a photograph of the phenomenon:
> Have any of you observed this? Do you know the cause or solution? It
> doesn't happen when we glow discharge on glass slides—but on the other
> hand, we we using the aluminum blocks for a couple years without issue
> before ever seeing this, and ordering a brand-new block doesn't help.
>
> Thank you in advance for your helpful replies,
> Jason Kaelber
>
> --
> J T Kaelber, PhD
> Director, Rutgers CryoEM & Nanoimaging Facility
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