[3dem] [External] Re: glow discharge "fireball"

[Morgan, David Gene]

To everyone who is putting parafilm into a glow discharge device:

I have always been told that the inclusion of something like parafilm in a glow discharge device changes the properties of the "glow" by including some unknown amount of hydrocarbon ripped from the parafilm.  This may or may not be true, and the overall effect may be minimal.  However, it is something I have always worried about and avoided except in devices that were dedicated to making carbon films hydrophobic.

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            David Gene Morgan
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________________________________
From: 3dem <3dem-bounces at ncmir.ucsd.edu> on behalf of Debakshi Mullick via 3dem <3dem at ncmir.ucsd.edu>
Sent: Thursday, February 5, 2026 12:08 PM
To: Jason Kaelber <jason.kaelber at rutgers.edu>
Cc: 3dem at ncmir.ucsd.edu <3dem at ncmir.ucsd.edu>
Subject: [External] Re: [3dem] glow discharge "fireball"


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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<mailto: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:
[cid:ii_19c2ec013ece2b5b9f31]
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

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