Hi,
I have a load of 395/400nm that I got years ago for making an expsoure box but never got around to it, and whilst they do a good job of making stuff fluoresce, the rather bright purple can wash out the more subtle glows of things like tonic.
So on a whim and out of curiosity I bought some very cheap 1W UV LED's, listed as being 365nm. It's always a gamble but for £2.10 for 2 delivered I was curious as to whether these really were 365nm.
Well, I tested them at a much lower current (50mA, then 100mA) as they are apparently rated for 700mA. And they emit a faint white - slightly yellowish glow that I was kind of expecting for this wavelength, but the output doesn't seem to cause flourescence in any of the usual suspects: highlighter pens, marks on bank notes, UV reactive acrylics - even printer paper which will glow very bright with UV doesn't really glow.
So I'm somewhat confused - I would accept that they just aren't UV, but they're far too dim to be anything else. Using a tube blacklight - that is so wide band it makes everything glow - I shone that on the LED to check for any kind of phosphor coating that some modern LED's have - just incase they were mislabelled and were some kind of phosphor LED, but no glow, so they definately have a bare die.
They also have the kind of weird glow I have seem from other mid UVA sources.
The only thing I can think of is that the lenses they have used are blocking much of the actual UV - preventing them from actually stimulating flourescent materials - whilst letting through the faint off-spectrum glow. That or they're lower than 365nm (doubtful).
Unless 365nm just doesn't make many things glow as well as 395?
The end goal here to have something a bit less power hungry and more direcitonal than the tube blacklight - but one that doesn't really emit much visible light. I suppose the next thing to try would be an actual 365nm flashlight that are all on amazon/ebay.
Here's the kind I got:
https://www.ebay.co.uk/itm/235034903272?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=gpe_tz_5S3q&sssrc=2047675&ssuid=haCVYFDCS46&widget_ver=artemis&media=COPY