With the busyness of fall harvesting it's a wonder I got any natural dyeing done at all. But I did and I love the results. I managed to dye 6 oz. of roving a medium blue with Japanese indigo, spun into yarn and overdyed with black oak bark. I prepared my dye bath by bringing 1 oz of dried oak bark almost to a boil, turned it off and let sit overnight. The next day I strained the bath and added alum, cream of tartar and tin using Bancrofts one pot method described in J. Lilies book.( I love this method, especially for roving). Along with the yarn I put 2 oz of white roving in the dye bath for a beautiful yellow. I simmered the bath gently for about 45 minutes. Turned off the burner until dye bath was cool. I then washed and rinsed the yarn and roving in warm water. I can spin these rovings as is or blend on my drum carder. The possibilities are endless.