Bill Moore is a stamp collector, but his search didn’t need to extend beyond his own mailbox.   You see, Bill knows a little secret:  pre-sorted stamps and regular stamps have a slight difference.   Pre-sort stamps aren’t checked as rigorously as the postage stamps you or I buy at the post office, so they are missing one security measure.   Standard postage stamps glow under ultraviolet light, but pre-sort stamps don’t.   That is, most pre-sort stamps don’t.  Moore, after scanning his mail every day with a blacklight, has found one lone example of a pre-sort stamp that got a dose of UV-paint.  A combination of issues, from the naked-eye invisibility of the paint to the assurance from the post office that the ink won’t wash or rub off, means that the printing presses that are used to produce stamps aren’t always cleaned completely between jobs.    Sometimes, full sheets get through the machine and collect a dose of the UV paint, while in other cases the result is spotty, with some stamps in a sheet getting phosphorescence while others are skipped.  The pre-sort stamps are produced in such enormous numbers, they’re hardly a rare commodity to collect, but Mr. Moore’s UV-glow stamp is certainly one for him to hold on to.

Collectors of all kinds should take a lesson from Mr. Moore:  ultraviolet light can tell you a whole lot about your collection.   Phosphorescence is a strange property, in which a certain chemical or molecule glows energetically under ultraviolet light.  The effect is striking, because we don’t see the UV light itself, so it appears that the phosphorescent object is illuminated from within.   To tell the truth, you’re probably phosphoring right now:  laundry detergents and toothpaste are two excellent culprits for making a person glow.  Ultraviolet light is a cheap and easily detectable way of revealing an object’s chemical composition, which makes it a very handy tool to collectors of all kinds.

Most glassware people know that vaseline glass glows quite energetically under a blacklight.  Sellers sometimes set up a blacklight to create a dazzling display of their vaseline wares, but it isn’t just for show.   There are quite a few imitators, and sometimes difficult-to-distinguish  relatives like carnival glass, so using a blacklight to check for vaselineware’s authenticity can prove the item’s value.   Incidentally, vaseline glass glows because of faint uranium content, which isn’t exactly dangerous, but means you probably shouldn’t eat off it — another characteristic worth testing with ultraviolet light.  Not all uranium-containing objects glow, though, so don’t trust UV light with identifying Fiestaware.  The construction and glass of the vaseline objects enhance the glow, giving them their otherworldly appearance.

Authenticating antiques goes beyond finding genuine vaseline glass.  Because much of our modern products phosphoresce due to the chemicals used in their creation, it can help in identifying fakes or reproductions.   Natural pigments so not glow nearly as much or as readily, which means most true antiques, those exceeding a century or more, will have far less of a preternatural glow when exposed to black light.     Even if the item is not a pure reproduction or complete forgery, items that have been ‘touched up’ with modern paints, re-glued with modern glues, or stripped with modern solvents are likely to glow under ultraviolet light.   That glow isn’t a complete guarantee of damage, though, as a story from art expert Fred Ross explains.   The painting at the right had been professionally cleaned, but just the face and hands.   One art appraiser interpreted this as evidence of modern alteration — they assumed the face and hands had been repainted later.  Ross, understandably, took the painting to a more experienced appraiser who recognized the difference between a fake and preservation.   Even though the UV light’s results still require interpretation, it can magnify telltales that would otherwise be far more difficult to detect.

So, you want to know where to get one of these ultraviolet light sources?  Aside from your local glowing-poster-headshop, even stores like Wal-Mart often have a small selection of blacklights amongst their normal lightbulbs.   Pet stores also carry them as a color-enhancer for tropical fish or lizards.   These kinds of blacklights will most likely require power from the mains, which makes them less portable than others.   For a portable version, return to your pet store:  small, pocket-sized UV lights are marketed as ‘pet urine detectors’, and usually cost under $20.  If you require something even smaller, companies produce blacklight pens, which resemble a laser pointer and are usually marketed as security devices, for writing secret messages or detecting fluorescent marks in currency.  Remember, blacklights are relatively low-powered, and any fluorescence they detect can be washed out by normal indoor lighting.   If you plan to carry one with when hitting the flea markets or antique shoppes, be prepared to find a dark corner or cover your head with your coat — both which could look quite suspicious to a seller, so check with the seller before heading someplace dark with their wares.   Just explain how important it is to check out the object for the sort of problem a blacklight will detect: it could be the difference between buying junk or a gem.

Vaseline glass is a type of yellow/green glass that is made by adding uranium dioxide to the glass mixture. Because of this special ingredient, it’s easy to identify true vaseline glass - when a blacklight is shined onto a piece of vaseline glass, it will glow a bright fluorescent green.

Vaseline glass was made in the United States beginning in around 1840 up until World War II. At that point the government prohibited the use of uranium dioxide in vaseline glass, and the ban lasted until 1959. To this day there are companies that produce vaseline glass, however because uranium dioxide is difficult to obtain, production is limited and the glass tends to be expensive.

To learn more about vaseline glass, please visit the website of Vaseline Glass Collectors Inc. http://www.vaselineglass.org/ where you’ll find plenty of photos of beautiful art glass, lists of manufacturers that made vaseline glass and some of their top products and links to other glass sites. The site also has several pictures of how pieces look with the blacklight shined on them, which is interesting. The group has a helpful newsletter that’s published 6 times a year as well as an annual meeting where members can get together to share information and discuss their favorite hobby.