as I must have told you before, my mother-in-law is a great cook and she uses really lots & lots of onions. (the yellow kind, not the red kind) And I've asked her to save the peels/skins for me, and she gladly does so. (so sweet) Last time I dyed with them was last May, three months ago, and I was eager to do a new bath. I've mordanted silk, linen, silk yarn, cotton crochet lace & vintage + handmade cotton crochet doilies, with alum. Boiled the onion skins/peels, then sank the fibers when ready. I didn't leave overnight, and rinced after a good couple of hours. It did bleed a bunch this time. And believe me or not, but onion skins/peels dye is the one that stain my bath tube the most ! And my nails too.
really, how can you resist getting such a hue with something that anyone can find in the kitchen ?