Lots of my research in natural dyes involves reading the books of sir Edward Bancroft, who promoted the use of the oak bark from the black oak as one of the finest, and most light fast yellow dyes of the time.
Oak bark is a substantial dye that does not need any mordant (because it has a high tannin content), but using alum will brighten the shade.
A higher Ph (Ph8) will darken the shade.
Use at 50-100% WOF for medium depth of shade.
Always soak bark and roots overnight before heating. Use a dye bag when dyeing wool or the bits will get stuck in the fibers. Heat slowly to below a boil, boiling may dull colours. No mordant needed but alum will intensify the dye results.
Finely cut chips packed in a reusable pouch of 100 gr (3.5 oz)