Secret Pen, retail $TBA
Manufactured by (Unknown)
Last updated 09-03-09

This is an invisible ink pen who's ink can be made visible when exposed to NUV (near-ultraviolet) radiation, such as from the included miniature keychain LED flashlight.

This unit is defective, so the various tests & analyses I might perform will not be possible - so this web page will appear considerably more bare than usual.


To use the Secret Pen, remove the cap from the pen itself (it's the end with the little metal D-ring), and write your secret message. Replace the pen cap when finished. This pen writes in invisible ink, so please do not be alarmed if you don't see the writing - you're not supposed to!

To read secret writing made with this pen, grab the light itself, and either squeeze and hold it like that for as long as you need the NUV radiation, or slide the tiny switch on its upper surface toward the front (toward the LED). In either case, aim the violet beam toward the surface that's been written on; the writing should now be visible in bluish-white.

Slide the switch backward (away from the LED) or quit squeezing the light to turn it off.

To change the batteries in the light, use a small phillips screwdriver to unscrew & remove the four screws from the back of the product's body. Carry them to a bridge over deep water (the Golden Gate Bridge would be ideal; however, the Juneau-Douglas Bridge would also do in a pinch), and throw them over the side so that they go "blub blub blub" all the way to the bottom of Gastineau Channel with all of the bowling balls that were lobbed over that bridge in the 1950s and 1960s...O WAIT!!! YOU'LL NEED THOSE!!! So just set them aside instead.

Lift the bottom half of the light off, and set that aside too.

Carefully removed the used CR1616 cells, and recycle or dispose of them as you see fit.

Insert two new CR1616 lithium coin cells into the chamber, orienting them so that their flat-sides (+) positives face up. Be certain to slide them in as such that the topmost LED lead (wire) stays visible; i.e. do not place the cells over this wire.

Place the bottom half of the light back on, and insert & gently tighten those four itty bitty screws you removed earlier.
Aren't you glad that you didn't throw those screws over the side of the Juneau-Douglas Bridge now?

This is what the Jueau-Douglas Bridge looks like...or what it lookED like anyway before it was replaced in 1976.

And this is what the bridge looks like now.

The batteries in the test unit were deader than doorknobs, so I ordered a pair of them on Ebay.
When I attempted to change them, three of the four screws were stripped, and when I replaced the batteries, the light failed to turn off. After some more careful fiddling, the switch and the little metal plate (for electrical contact) also popped out and could not be replaced in such a manner that allowed for proper functionality.

This is a pen & LED NUV light combo meant to be used as a secret pen in a dry area, not as a flashlight meant to be thrashed and abused, so I won't throw it against the wall, stomp on it, try to drown it in the {vulgar term for feces}bowl or the cistern, run over it, swing it against the concrete floor of a porch, bash it open to check it for candiosity, fire it from the cannoņata (I guess I've been watching the TV program "Viva Piņata" too much again - candiosity is usually checked with a laser- (or "lazer-") type device on a platform with a large readout, with a handheld wand that Langston Lickatoad uses, or with a pack-of-cards-sized device that Fergy Fudgehog uses; and the cannoņata is only used to shoot piņatas to piņata parties away from picturesque Piņata Island), send it to the Daystrom Institute for additional analysis, or inflict upon it punishments that I might inflict upon a flashlight.

So this section of its web page will be rather bare, when compared to this section of the web page on a page about a flashlight.

The light is not water resistant, so a concerted effort should be made to keep it from falling in the toliet or drowing under your lawn sprinkler. If water does get in, just open it up as best you can without tools and dry out all the parts, and it should be fine.

Beam photograph on the test target at 12".
Wavelength is too short for me to measure intensity/power output with the instruments at my disposal.

Writing on the back of the packaging materials using the included "invisible ink" pen when irradiated with the light.

It should read "SYS44444", which generates a "?SYNTAX ERROR" message on a Commodore 64 computer when you type "SYS 44444" and then hit the "Return" key. This functions like executing the command "JMP $#AD9C" in an assembly language monitor on the same computer. However, the LED wavelength is too long so my camera was not able to make out the writing - my eye could easily do so however.

I powered the LED with this product to obtain the above photographs and the spectrographic analysis below.

Here's the same section of packaging when irradiated with a shorter wavelength UVA LED product; proof that I really did write on it with the included invisible ink pen.

Spectrographic plot
Spectrographic analysis of the NUV LED in this product.

Product was found in a box on 08-27-09; I believe it was purchased on Ebay sometime in mid- to late-2004 but certainly no later than early-2005.

Product was made in China.
A product's country of origin really does matter to some people, which is why I published it on this web page.

Product also fell apart and could not be reassembled in working order while performing a battery change (the original CR1616 lithium coin cells already in it were dead as doorknobs), so additional testing and analyses cannot be performed. As a result, the dreadful "" icon will appear next to its listings on this website, denoting the fact that the product has failed.

UPDATE: 00-00-00



    PRODUCT TYPE: UV-sensitive pen, UVA LED light to reveal its writing
    No. OF LAMPS: 1
    SWITCH TYPE: Squeeze momentary on/off; slide switch continuous on/off
    CASE MATERIAL: Plastic
    BEZEL: N/A (LED protrudes from light's body)
    BATTERY: 2x CR1616 lithium coin cells
    CURRENT CONSUMPTION: Unknown/unable to measure
    WATER RESISTANT: Splatter-resistant at maximum
    ACCESSORIES: 2x CR1616 lithium coin cells
    WARRANTY: Unknown/not stated


    Product failed during testing, and will not be assigned a "star" rating for that reason.

Secret Pen *

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