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Chmistry buffs: IR invisible ink? Answered

Hey all science-type people,

I've seen invisible ink pens and things for sale that contain ink that show up in infrared, instead of ultraviolet light.  That's really appealing to me for a number of project ideas because digital cameras pick up IR exteremely well (especially with their filter removed).

The problem is I think I'm going to want a lot of it, and those dumb little pens are crazily expensive.

So any of you chemistry buffs out there have a secret formula I could make?  I'd prefer something invisible in regular light, but hey, whatever you've got. :)

Thanks in advance for your help,


I make IR ink. I also have the filters needed to see the ink. Contact me for more info


Anyone had luck with making the IR ink?

Indocyanine Green should do it.


Thanks! Good lead, but from what wikipedia says it has a half-life of like 2 minutes. Rats.
So I don't know if that'll really cut it. (Unless I'm missing something, which is entirely possible)

But that did get me hammering on wikipedia more, where I found this:

Unfortunately there are no articles for any of the IR "Fluorophores". (Plus that's also me making the assumption that they are IR-visible outside a glowstick.)

Anyone know any more info on Fluorophores? Or any tips on how to buy dihexyloxyviolanthrone from Walgreens? ;)

That's in vivo it's metabolised rapidly by the liver.


An ink that is invisible in normal light, but shows up under IR light?

Or an ink that is invisible until observed through an IR camera?

Do you have a link?


$18.50 per pen... so um, yeah, the ink is probably like $10/oz.

Ah, an ink that is invisible until observed through an IR camera.

I understand - it fluoresces in the IR. I thought you meant it fluoresced under IR light.

Have you tried googling for infra red fluorescence?

. See if you can find out what is in the pens (might find an MSDS or similar on manufacturer's web site) and buy the material(s) in bulk.

I found this. All greek to me, but it probably says something important.