Last night, my husband and I went to the Minnesota State Fair and stumbled upon a demonstration of a linotype machine, a semi-automated, mechanical printing system that was used by newspapers and magazines (and basically everything else) from the end of the 19th century through the 1970s. It's a completely mesmerizing piece of equipment. An operator types out a line of text and the machine responds by collecting molds that match each letter and fitting them together. Then, it fills the mold with molten metal and dumps out the freshly minted block, ready for the printer ... before automatically re-racking all the letter molds so they're ready for the next line of text.
It's incredibly cool and I could have watched it work for hours. But then my husband thought to ask about what metal they were melting and pouring into the molds. Turns out, it was lead ... and my pregnant butt was hustled out of the building. I found a great video to show you, though — a 1960 educational film meant for future linotype operators. The full thing is way longer than you actually probably want to watch, but I've set it up to start right at the beginning of a really great explanation of how the thing works. Watch it from where the video kicks in to about 6:30, and you'll get a good 3-minute demonstration. You can also see linotypes doing their thing in the trailer for a documentary that Rob posted about a few years ago.
Also, there's at least one newspaper in the United States that's still being printed this way! (Thanks, Kyle Whitmire!)
Maggie Koerth-Baker is the science editor at BoingBoing.net. She writes a monthly column for The New York Times Magazine and is the author of Before the Lights Go Out, a book about electricity, infrastructure, and the future of energy. You can find Maggie on Twitter and Facebook.