Does repeated scanning damage banknotes!

A question which I was recently asked by a bank archivist! Could the light from a scanner lead to damage in the form of eventual fading of ink or degradation of paper.

It raised several sub- queries in my mind

I would split the question into several parts:

1. Can old scanners [those using bulbs] damage notes.

2. Can modern scanners using LED light sources damage notes?

3. Would UV light damage notes.

4. How often can a banknote be exposed to an intense light source before damage is likely to occur?

I would like to know about this also. It might be possible to test this, and I already have a bundle of 100 notes that is being kept aside for testing contaminants and UV.

As I have a mains-powered UVC lamp I can expose one of those notes for a few hours and then compare the UV response under UVA and the white light scan appearance to control images which I already have.

It seems to me that UVC is the most likely wavelength that will cause damage, and it also seems to me that about two hours exposure is the upper end of what a note is expected to endure.

The other one to test is infrared at 980nm. 

Just last night I successfully photographed anti-Stokes fluorescence triggered by three LED bulbs emitting infrared at 980nm. Each bulb is 15W and they have to be quite close to the note in order to trigger the fluorescence.

The catalogue modification is awaiting approval, but have a look at 10 Apsars - Abkhazia – Numista

In fact that note might be the all round best test subject because it has phosphorescent properties also, and it would be good to see if that is hurt by long term UVC exposure.

One more item of interest: I recently bought two 100 Apsars notes from the same vendor. One was in a set of three notes (10, 25 and 100 Apsars) and the other was by itself. They are 6000 apart in terms of serial numbers. The later one has quite weak anti-Stokes fluorescence, compared to the earlier one.

We therefore have variables at the factory. So the tests would have to be using one note and comparing its pre and post exposure images.

The 10 Apsars note is cheap enough to destroy but there is no way I am playing with any of the other denominations. They are not so cheap.

I haven't found a paper on it yet, but did find an opinion of the Bank of Canada.

https://www.bankofcanadamuseum.ca/2023/07/caring-for-your-bank-notes/

And this, from the Library of Congress

https://www.loc.gov/preservation/care/light.html

Neither tells us much that we don't know already.

LED light sources are the least destructive [which we know].

We also all know that a banknote framed behind glass in a bright room will fade after some years, (or decades?)

There are people I can ask, when I get hold of them!

Every photon with the right energy can hit a pigment at the right, or better wrong time/place and alter it's bonding or structure leading to loss in vibrancy.

But I am quite sure that you would not scan one and the same note so many times that it would matter. Handling the note to scan it so many times will damage it way more likely.

But I wouldn't leave valuable notes out in direct sunlight though.

I do not believe scanning a banknote once or twice can have any impact to the note. On the other hand, if you scan them 100 of times then I cannot say the same as if that happen, it is just like leaving the banknote to expose it to the sun for a period of time.

I can show you a note and there is no way you can tell me if the note has been scan or not. At least you cannot tell from the naked eye.