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So, happened to me last night on an instructor course.

I usually carry a couple of cylume sticks in my headset bag, and doing some night flying for the first time in quite some time, I decided when we flew through dusk to crack one out of its wrapper, and bend it to activate it.

At which point the plastic was clearly sufficiently old it had got brittle. The thing snapped in half, and glowing liquid went all over my trousers, kneeboard, hands, and yoke.

I handed control to my instructor, got my handkerchief out, and wiped off my glowing hands and kneeboard, then carried on. For the rest of the flight however the odour of the stuff was quite strong and unpleasant, although the packaging assures me - non-toxic (and I did have a torch as well!).

Post flight as I went to wash it off my hands properly (and get rid of the smell!) I spotted also that the broken plastic had clearly also been sharp enough to cut my hand, although not badly and it had stopped bleeding by then.

I tested a second one later holding it over a bin in the clubhouse, and it also had no flex in it whatsoever.

I suppose my lesson from this is that whilst they've got their place, and they're useful, if they're in storage for a while, test them carefully before bending them, perhaps bend them first in the foil packaging. If the plastic seems to break rather than bend, leave them in the packaging and dispose of it when you can. Don't just simply use them.

Well there you go - not in the end a serious accident, but could have gone worse if I'd been less lucky, or reliant upon them as my main cockpit torch.

T6Harvard liked this
I made the joke about glowing testimonials in another thread...

I think there's glass inside those things, that's what breaks when you bend them. That could be what cut your hand.

If anyone wants to convert a torch to red, I have some Quality Street wrappers now after Christmas.
It being a long time since the CAA stole my qualification to fly at night, can you tell me the purpose of firing up one of these sticks in the cockpit when bimbling along in the dark?

I realise on this occasion it was a simple test from curiosity, but what's the scenario where a flyer might think to himself "I wish I had one of those glow sticks that @Genghis the Engineer always carries"?

Rob P V2.0
I find that the "6hr glowstick" is in reality a 90-120 minute glowstick, but that's as long as most night flights occur anyhow, and it's a useful addendum to the torch, clipped to my kneeboard, it lets me read the PLOG, chart, etc. fairly readily. I tend to use white or green - the red ones aren't really bright enough.

Maybe it just panders to my love of non-electronic gadgets, but it works for me. When it's not spraying glowing fluid and my blood all over the cockpit anyhow.

Rob P V2.0, riverrock liked this
P.S. I just found a couple more of those cylumes - I'd bought a pack of them a few years ago, and found an expiry date on them, which was in the middle of 2021.

You'd sort of assume that the expiry would be down to the illuminating chemicals, but perhaps here it was in fact down to the embrittlement of the plastic.

As somebody who doesn't normally look at the expiry date on a pack of bacon, it had never occurred to me before to look at the expiry date on one of these !

Well, a year and a half, but nonetheless, it's a fair point Dutch, on the other hand at about £1.30 each, perhaps it's just what it is.

I still like having them in my headset bag, and have ordered a new pack of 10, but the remainder of this pack are all going in the bin unless I happen to think of any fun science experiments I can do with them.

We recently found a box of unopened cheap cyclumes that we'd bought a year ago for my daughter's 9th birthday party (silent disco); on discovering the box my son dived in and started cracking them, only to realise that they do indeed crack and go brittle very quickly!

We used to use them when walking the dog at night - we'd stick one around his collar for when he went off the lead in the fields.