The Mystery of the Dark Fax

I left a really old fax in my hot car and it turned black. What happened?

You must be a real pack rat! It had to have been a thermal paper fax. Back in the olden days of the 1980s and early 1990s, most fax machines still used thermal paper. It was slick and shiny and came on long rolls. You can still buy it but it’s hard to find and pricey.

Thermal paper is coated with a colorless dye, and the chemicals in it react to heat by turning black. It sounds like you’ve had your own little science experiment right there in your car.

Thermal printers were, at the time, cheaper to construct and used few moving parts. Also, users didn’t have to buy ink because it was already embedded in the paper! The print heads would heat the paper, forming letter-shaped images. Some of the fun side effects of having an office fax in the early days included losing faxes behind desks because of their curly nature, as well as hearing your boss curse when a “junk fax” came through, wasting expensive paper. Eventually, thermal-printing fax machines gave way to inkjet machines, which used the more accessible and less costly standard 8 1/2-by-11-inch office paper.

Take heart: Even though it dates you to be toting around thermal paper faxes, at least you don’t remember the days of schoolteachers passing out purple-lettered mimeographed copies and watching students, en masse, pick them up to smell their inky goodness. Oh, wait … you do? Sorry!

Do you have a question about faxing? Send me your fax question.