Looking for a UV Light

Phil , It kind of depends on what you want to use it for. If I was in the market for a UV light, I would get a dual wave, because various uses require one or the other. Long wave is the way to go to detect repairs made to stamps and, if you want to detect tagging, it will depend on the country and when the stamp was issued. Here are a few examples:

Short wave - US, Britain, Finland, older Canadian, Israel, older Mexico

Long wave - Russia, Norway, Canada, British definitives issued after 1992, France, Hong Kong, Taiwan, Mexico (newer issues)

As you can see, if you collect Canada, Britain or Mexico, you will need each type of light in order to detect tagging throughout the years.

I hope this helps!

I have always stayed away from philatelic-branded UV lamps, and have always advised others the same, for numerous reasons: they are way too expensive compared to the non-philatelic equivalent, they are underpowered, they aren't filtered, hard to see anything in normal room lighting... I was fortunate enough to have visited a brick-and-mortar store that had UV lamps so I could test them, and found they were woefully insufficient for what I had intended for worldwide tagging studies.

I've always used a large dual wavelength corded lamp. Granted, it's from my research days (I traded a professor 5 years of science journals for it, as neither of us had future need for what we had. It's overkill, as it was research grade.

However, you can get a near equivalent from manufacturers such as RayTech, which will do more than the philatelic UV lamps and are more powerful. Among collectors, these are often used by rock/gem collectors. You should be able to get one similar to mine for ~$100 and you won't regret it. They are about the size of a long brick, but not that heavy of course. I've used mine for over 30 years (it is research grade and originally cost $200+ back then; I can light up a full pane with it. Unfortunately, that also means they aren't battery-powered (which is fine with me) and you have to be a tad bit careful about looking at the lamp directly or reflecting off metal surfaces. It won't blind you instantly, but long-term if you aren't careful, you can get some retinal damage. This actually happened to a research buddy of mine who was using a much more high-powered lamp and allowed it to reflect off his metal vacuum chamber for hours on end.

Before I left the house, I did take some quick cellphone pics of my lamp and also some sample examples of lighting up an entire pane of stamps. I'll post them tonight when I return home.

If you aren't in a hurry to purchase a lamp, I can see if I can drop it off for you play with next time you stay over in Houston. That way you can see if it does what you want.

SWUV is the very thing that makes viewing an eclipse with the naked eye dangerous. Retinal damage from SWUV is permanent, and cumulative. You always want to make sure that the lamp is angled so that the rays reflect away from you. Even so, you will be exposed to a certain amount of stray backscatter. Phosphorescence manifests as an afterglow, so I use the lamp in the dark, close my eyes as I switch it on, then open them as I switch it off to view the afterglow. This technique guarantees minimal exposure.
On the other hand, long wave UV (black light) has always been considered perfectly safe, but recent work seems to indicate that that may not be entirely true.
One more thing. Because the foil strips on Hagner pages are SWUV-impervious, items must be removed to be lamped. That's probably true for other clear mounts as well, if they are touted as 'archival'.

So I should be looking for a lamp that has wavelengths of 254 & 365?

Yes, but those are pretty standard plus/minus 10% depending on the UV source. One big difference between research/commercial grade and consumer grade is that the former is filtered (which in research is critical because the excitation wavelength is strongly relevant). This also translates as a specifications difference...

I have noticed that the specs on consumer grade devices, especially the philatelic branded ones, are to be taken with 1000 grains of salt. They use the individual parts specs, rather than the actual device output specs. Those little lamps may claim 4W, but the actual wattage output in the UV spectrum of interest is much much less than that. My 6W research grade lamp can light up a whole pane of stamps in low light environment -- you couldn't do that with a philatelic branded lamp even in the dark.

Keep in mind, this will depend on which country you plan on checking for tagging. On some GB, especially the early phosphors, neither standard wavelength works well.

I've looked around and haven't seen any of those lamps you mentioned here but that is good to know.

Phil ,
www.ebay.com/itm/363507908029?var=632729163656&hash=item54a2c27dbd:g:X-QAAOSwh21cUrV-

UVA lamp, 315-400nm range.
US$2.67, free shipping.

So here is the top view and underneath view of my UV lamp:

It's a little larger than my foot (I figured you didn't want my foot in the pic for comparison).

There's no need to buy this brand, as it is overly expensive (remember, I traded journals for it!) and is overkill for basic philatelic purposes. The comparable RayTech is more than sufficient and should be ~$100 or less. Even that, will be more than you likely ever need for studying stamp tagging/paper.

I'll post some sample photoluminescence pics...