UV cross-contamination when shipping notes

I always suspected this was a “feature” when multiple notes are sent in one sleeve, but today I got definitive proof.

I ordered three notes from a guy on eBay. All three are uncirculated and all three are perfect when viewed under normal circumstances.

However when I did the UV photographs I got a nasty shock. 

A Cambodia 500 Riels note had gold UV activity on it, which is not normal for that note.

See here:

The reason this stood out to me was because I knew that a Colombia 200 Pesos Oro note that came with this one, has gold UV activity. Sure enough when I photographed the two notes together, the source of the contamination is found:

You can see especially on the left, how the Cambodia note picked up UV ink from the Colombian. I brushed that with my finger and it didn't budge, so I resigned myself to having a contaminated note.

But…on a whim I got a microfibre cloth and wiped the obvious gold areas with that cloth. Amazingly, it removes the contaminant but does nothing bad to the note. Here is what is looks like now. This is with a quick wipe, not all the areas have been carefully done:

What this means is that there can be cross-contamination of notes if they are shipped in the same sleeve, which most people do.

From now on I will ask sellers to put high value or rare notes in their own sleeves. 

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I do find it a bit surprising that the UV active ink would transfer so easily! I wonder at the print quality of some of these banknotes where ink can migrate so easily…

Hibernia

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I do find it a bit surprising that the UV active ink would transfer so easily! I wonder at the print quality of some of these banknotes where ink can migrate so easily…

Yes, it is surprising & disappointing. I get batches of notes shipped to me all the time together, like you have described. It makes one wonder how much does it effect each note. I have also shipped notes in batches but usually they're Bank of Canada notes & I don't think they would have that problem (especially polymer). At least, I hope not!

The carrier resins for the UV pigments seems to be relatively brittle, maybe a batch with not the best mix of oligo- and monomers.

I have some tests planned. It seems to be a common occurrence with notes in my collection but I concede that a lot of those are from the 1980s and 1990s.

I have not seen it on Irish or Finnish notes from the 1980s and 1990s.