Strange filmy substance underneath micro-switch ST domes

[juryduty]

In taking apart this Micro-Switch SC keyboard I found a strange dry filmy substance that had been slathered all over the membrane.

My guess is that this was placed there intentionally and is not a spill of a beverage or something like that. This is based on the fact that it appears to be "evened out" so it covers the whole membrane and has no obvious entry/exit point. This could be totally wrong, I don't know. If I had to guess what it is and why it's there I would say it's something to maintain dryness (like the powder on latex gloves) or some kind of rubber conditioner/preservative.

Anybody else got a guess or seen it before? The reason I'm asking is that I don't know if I should scrub it off before reassembling.

thanks in advance...

2017-11-11 00.12.46.jpg (3.25 MiB) Viewed 1478 times

2017-11-11 00.12.56.jpg (2.93 MiB) Viewed 1478 times

[seebart]

Hmm interesting, from what I remember there was nothing remotely like this on my Grid Compass keyboard.

keyboards-f2/honeywell-d3013-t17169.htm ... =honeywell

[Engicoder]

I have 3 or 4 ST boards and have not seen this before. Could you give us more information on the keyboard itself, date and Honeywell model number (i.e. XXXSTXX-X-X)?

[snuci]

No, nothing on my IBM Unsaver either. photos-f62/ibm-73x3832-quiet-touch-comp ... 13661.html

[griefdad]

Found something similar in a GRiDCASE 1 from 1986 (which, as far as I can tell, has nearly the same keyboard as the compass mentioned by seebart, mine has the cat. list. 71ST22-1-T)

I had assumed that it was caused either by the EL display, which had been damaged during shipment and leaked its contents into the body of the machine, or by the environment in which it had been kept (signs of moisture damage throughout the case).

Origins aside, if the substance is the same as what I ran into, I can say that if you do decide to clean it, make sure to get it all off. I thought a quick bath for each dome would be enough and realized later that the film which had not been totally removed had formed into some pretty unsightly (and now apparently green, which is a new a development) residue.