Spy fluid

In another thread Tripler wrote:

Back in the '80s I worked in a classified environment. During one of our security briefings we were told about a fluid that would allow a spy to read what is inside of an envelope, which would evaporate without a trace. An obvious countermeasure was suggested.

Question: Did this stuff have a ‘trade name’? Like, could a spy go into the local spy store and ask for a bottle of PaperView? Or is it just ‘old VCR head cleaning fluid’ or some other ad hoc substance?

IIRC, there was an MSDS form for VCR head cleaning solutions and it was Anhydrous Isopropanol. If you wet an envelope with it you can read the letter inside if it is not folded. It will evaporate 100% I think…

Probably some variant of this. You can observe a similar, albeit more permanent, phenomenon at work by rubbing oil on a piece of paper–the oil makes the paper semi-transparent.

All the VCR head cleaners I’ve had contained the aforementioned isopropanol. But:

  1. Most inks are soluble in alcohol. The ink on the envelope and letter would smear.

  2. The spray in Q.E.D.s link doesn’t have spec sheet that I could easily find, but it does say non-flammable, so that rules out alcohol. (Unless they are not telling the truth. There’s a lot of that in the snooping world. Hardly surprising.)

That sounds like the stuff they were talking about. They did mention an aerosol.

I always used 1,1,1-trichloroethane (for head cleaning, not spying), but I don’t know if it’s still available. Also, I suspect it’d do its solvent mojo on the ink.

Here’s the story on my “discovery”:

When I was a kid, I remember rooting around in our TV cabinet one day for a videotape during a summertime day–basically looking for a movie to watch back whe VCRs were around (like, maybe 19, 20 years ago. . .)

Anyway, I came across this VCR head cleaning kit, which had this ‘fluid’ in it. Being the smart kid I was, I opened up this little bottle wondering why someone would put a fluid into a VCR (knowing that liquids and electronics rarely worked well together). I noticed it evaporated from my fingers, presumably from my body heat. I dropped a bit onto a piece of nearby newspaper, and found I could read through it. Naturally, I instantaneously developed a multitude of situations in which to apply my newfound knowledge: report cards, progress reports, Christmas presents, etc.

I remember reading the ingredients on the side of the bottle, but that was so darn long ago the exact mixture is hazy to me. I do remember there was some sort of alcohol (isopropyl) and formaldehyde in the mix, so I was always careful. I also remember that none of the inks at the time ran–but I don’t recall if I ever tried it on ‘wet’ ink.

So, that’s my inadvertent childhood discovery turned into practical knowledge for you.

Yeah, I admit, I wanted to ‘preview’ my school progress reports before my folks actually opened them up. Who wouldn’t? :dubious:

Just based on whats written here, pentane or carbontetrachloride may do this while being too non-polar to smear the ink significantly. Trichloroethylene would be similar, but more polar so more potential for smearing.

I had some of that exact stuff once. It did what it claimed to do, allowing one to see through an envelope for half a minute or so.

Where the pruduct makers are lying is this statement:

the envelope will return to its original state, leaving absolutely no markings, discoloration, or other indications of use.

This is untrue. For while there were no visual indications that it was used, it stunk to high heaven like petroleum. And the stench never, ever, went away. Ever.

Anyone who picked up said envelope, even weeks later, would immediately smell petro.

Liquid freon will do this. Many years ago, when I worked in an automotive warehouse, we would occasionally drip some R12 out of a can into a bottle cap and then “accidentally” spill it on somebodys invoices, making them think we spilled water onto it.

The freon would turn the invoices transparent and you could see through 2 or 3 layers. It would evaporate quickly and didn’t warp the paper or smudge the inks.

Also cleared out that nasty ozone we had hanging around the warehouse.