Practical and interesting uses for your
This chapter looks at some practical and interesting
areas where you can use your black light.
Invisible ink pen and secret messages and security
A useful, fun and inexpensive tool is the
invisible ink pen. Looking similar to regular felt tip pens,
they write with ink that is invisible in daylight but fluoresces
brightly in the dark under UV light.
UV ink pens are widely available online, including
at amazon.com and eBay. Many sellers of black lights sell the
pens. You might be able to pick up some UV ink pens when you
buy your black light.
People use invisible ink pens for a wide variety of purposes
including writing secret notes to friends and, as described in
a later chapter, making glow in the dark sketches and art.
Invisible ink is often used to secretly mark
objects, including vases, painting, prints and documents for
later identification. A family might mark the bottom of valuable
heirlooms in case of theft or dispute. You might write you name
on the back of a painting. This will aiding to show it was yours
in case of loss. If the marking was written in visible in, a
thief may simply scratch it off or mark over it. With invisible
ink the same thief will have no idea the painting is marked.
An online seller or brick and mortar store
of radios parts or dolls may have a problem with customers who
return damaged goods they didn't purchase from the seller. If
the seller puts an invisible ink mark on the back of the items
before sale she can be sure that the customer is returning the
UV ink hand stamps for dance clubs, bars
You can buy UV ink and ink pads for your rubber hand stamp. These
can be used for secret marking like with UV ink pens. Clubs often
stamp the hand of patrons with invisible ink. This allows the
patron to leave and return, while allowing the club catch those
trying to sneak in without paying.
For identification purposes, Major League
Baseball put a fluorescent stamp on the ball Barry Bonds hit
for his record 73rd home run in 2001.
Judging the authenticity of drivers and
Most state drivers have markings that are invisible except under
backlight. Others cards, including credit cards, often have similar
UV fluorescent markings. Black lights are used to help identify
forgeries and counterfeits. Alterations to these licenses can
often be detected with a black light, as the added paper, glue
or other material might stand out from the rest of the license
and other untampered with licenses.
Checking the cleanliness of kitchens and
Under black light, otherwise invisible stains in sinks, tabletops,
bathroom floors and the like can fluoresce under black light.
They often fluoresce yellow.
Black lights are sometimes used to check the
cleanliness of motel and hotel rooms, public bathrooms and the
Testing if Glass Blocks UVA and UVB Light
Glass that blocks both UVA and UVB light is used for protecting
art, collectibles, clothing and other items. Sunlight, and even
artificial light, can fade paintings, prints, autographs, posters,
rugs and other items. UVA and UVB blocking glass is also used
to protect humans from damaging sun. Though not a definitive
test, you can use your black light as a quick test if glass blocks
UVA and UVB light.
Most standard glass, including for windows
and art frames, block UVB but not most UVA. Your black light
gives off only UVA, and you can assume the glass blocks UVB.
To test the glass, you need something that fluoresces very brightly
under black light, like white paper or a tennis ball. In the
dark, shine the black light at the glass with the fluorescent
item on the other side. If the item fluoresces very brightly,
the glass blocks the black light. If it doesn't, the glass appears
to block both UVB and UVA.
As your black light gives off a specific wavelength,
not the whole UVA range, this isn't a complete, laboratory test.
However, it still is a fair test. Glass that allows UVA light
through will be obvious.
Finding Scorpions in the Dark
Many scorpions fluoresce under black light
Finding rats and mice
As rat and mice urine fluoresces under black light, exterminators
and biologists trace the rodents with black light. You will often
see the pest exterminator carrying a black light. I've seen two
sitcoms where a pest exterminator used a hand held black light,
King of the Hill and King of Queens).
Examining art and collectibles: Introduction
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