Remember those books with swirly, patterned plates on the front and rear covers? Here's an awesome short film about the Cockerell Bindery, which produced marbled paper in a surprisingly handmade process. It's beautiful, retro, and super-British. If you just want to see the color marbling process itself, zoom ahead to 3:00 and watch the colors being applied.

This is one of those things I never thought to wonder about, but seeing it happen, I'm astonished at the craftsmanship involved. Humans are amazing. Enjoy:

If you're interested in creating marbled paper, here's a tutorial covering various methods.

(Via Kottke.)