So I was tooling around online and saw this headline. Naturally, it begged for some clarification, like where was this published, was it a joke, and just how invisible are these pens?
Fortunately, it didn't take much digging to get some answers. Turns out that this ran in the Columbus Dispatch in Columbus, Ohio about four years ago, and it wasn't a joke. Shoppers really were having a hard time finding invisible ink pens.
See, it started out with copper theft. That's a problem in both the UK and US that involves people stealing electrical cables and other items that contain copper so they can sell them to scrap metal dealers.
In Columbus, it seems, thieves were stealing entire air conditioners because they contained copper.
City officials responded by recommending that residents mark the insides of their air conditioning units with invisible ink. That way, if someone tried to sell the copper inside to any reputable scrap yard, the scrappers would check for the markings and know that it was stolen property.
The invisible ink pens they recommended use ink that only shows when exposed to ultra-violet light. People weren't sure where to buy the pens, so the newspaper kindly suggested some options.
Invisible ink pens aren't all that hard to find, it seems (you can find them at Amazon, too). The headline, of course, ended up being more fun than the story.
But, at least now I know a trick for protecting against copper theft. And, I even learned to make cheap UV ink pens with some hot water and a neon highlighter.