Phonetics and countries aside, a moire /mwär/ is a pattern of irregular lines produced by the superposition at a slight angle (or offset spacing) of two sets of closely spaced lines. Moire patterns or moire grids are commonly used on banknotes as anti-scanning (counterfeiting) devices, how effective moires are in helping the layperson identify counterfeits or preventing counterfeiters from producing fake notes is topic for another day. At any rate, this all started with an effort to obtain better quality images of my banknotes I thought "hey why not try scanning them, brilliant!", as I was browsing through the first scans and thinking "these don't look as good as I had hoped." the subject of moires and security features popped into my head. Hmmm. Well, ok, lets dive a little deeper.

("I'm not going to get to involved here so I'm just going to stick with one note and one particular area of the note to hopefully get a better grasp of what a moire pattern is/does." I said to myself, knowing full well it was a lie.)

But I will stick with one note and one area for this journal entry. The guinea pig for my moire investigation is the 2013 50 Hryven (Pick 121d) banknote from Ukraine, and the area I'll be looking at is in the upper left corner, on the front of the note, comprising of a light purple rectangle with the words НАЦіОАΛЬНИЙ ЬАИК УКРАЇНА (NATIONAL BANK OF UKRAINE) inscribed within the area along with the signature of the Governor of the NBU.  When first glimpsing this note from a distance (again focusing on the area mentioned above) a faint pattern can be discerned, it looks grid like but is hard to identify (for me). Upon closer inspection I begin to notice a repeating diamond pattern created by gaps between the lines in the (moire) grid. Ok, what else? 

(Picture of the obverse of the note.)

(Picture of moire grid, "diamond" pattern evident from a distance.)

(Picture of gaping between lines of moire grid, creating a "diamond" pattern.)

By now I've probably inspected this note a dozen times with and without my loupe. I'm thinking "well is that it?", nope. I take a step back from the note itself and start going through images I had previously taken, enlarging them, rotating, etc. While doing this I notice a repeating "square" pattern in the same moire grid. How the heck did I miss that! It was so painfully evident in the images that I'm embarrassed to say that I didn't see it. From a distance, it was not evident to me (still isn't), using my loupe it is visible but doesn't jump out at you, especially when I was fixated on the gaping and offset line patterns. I'm thinking it's just one of those things where some people will see "diamonds" and some will see "squares". It's basically a 3D puzzle to me at this point.

(Moire grid appearing as "squares".)

One more surprise left, after further inspection of the images I had taken another pattern became evident to me. This effect is a little harder to see and I haven't been able to notice this with the naked eye or loupe, only through photography so far, but the lines in the moire grid merge at a distance and form a square "maze like" pattern in the field. (Sorry about the pics, best I could do at the moment.)

(Moire grid lines merge to form larger "maze like" patterns)

Finally, what does the moire grid look like when scanned? After all this is the main purpose of the moire on a banknote, to prevent counterfeiting in the form of scanning and printing notes. Well, the moire grid disappears as it should (as I believe was intended), although the line breaks are still evident. To me it's a bit anticlimactic, at least for that particular moire on this note.

(Scan of note in PMG holder.)

To me, a moire (in this instance) is a cool feature but to call it an anti-counterfeiting is a bit of a stretch. If the moire, when scanned revealed a hidden message like "NOT LEGAL TENDER" or "DON"T F***ING ACCEPT THIS NOTE" I think that would be more effective and hilarious. One other thought, I've tried searching PMG for an article related to this. I've tried several different word and phrase combinations but am not finding anything related to this. So PMG if you're reading this HOOK A BROTHER UP and release an article about this in the near future, I'd be curious to see what you have to say about this. On a side note there are several articles out there about moires and moire fringes or patterns, all worth reading if you get a chance.