So, I'm starting some real dyeing at the moment, but I thought I'd share my sort of ridiculous first attempt. Basically, I filled a pot with water, vinegar, and nails, boiled them, left it for a day, then dunked some fabric in there for half an hour, and rinsed. As far as I can tell, because iron is a mordant the dye should be fast, but I guess we'll have to see!
The different colours you're seeing: the bottom is original colour (it's an old sheet), the middle one was in the iron bath for only 15 minutes, and the top one was in for 30 minutes. I like how suttle of a peach colour it turned out, but I'm looking for some more dramatic colours this week, with tea, beets, black beans, onion skins, avocado skins, and red cabbage.