Tie-dyeing, one of the quintessential summer camp arts and crafts activities, leaves the camper with a souvenir t-shirt or bandana that’s both unique to them and a wearable memory. We asked Atlas Obscura Course Instructor Aaron Sanders Head, a textiles artist who focuses on natural dyes, to share an easy guide to creating your own version of this summer camp tradition. One of the most vibrant sources for dyeing fabric is probably right on your kitchen counter: onion skins. Many food waste items generated while cooking dinner can be used…