Here's some interesting info from FW and a second source;
Why go to all the trouble of making your own coloring concoctions when you can get reliable, ready-made stains at the corner paint store? First of all, using a dye instead of a stain allows you to color the wood without adding a cloudy layer of pigment that can conceal the grain and cover up the wood's natural beauty. Unlike paint or stain, a dye consists of a liquid medium-usually water or alcohol-in which pigment particles are dissolved, not merely suspended. Thus, the pigment can't settle out. And since these dissolved pigments are less opaque than suspended particles, a dye solution is more transparent than a stain.
The palette of color-creating substances compatible with yarn and fabric is vast, yet relatively few of these materials have been adapted to the wood-dyeing craft. One of the most useful and well-known of these dyestuffs is brewed from the hulls of walnut shells by so simple a means as a pot simmered on the kitchen stove or by extracting the dyestuff with ammonia. This venerable brou de noix, which Jon Arno wrote about in FWW #59, produces very handsome rich-brown colors when applied to wood. FW #66
Have you ever noticed black blotches, dotting back roads through the countryside? Or stained your hands, peeling away the bright green hulls of black walnuts? Then you're aware of their powerful pigment.
Personally, I've yet to discover a good way to remove black walnut stains. Time seems to work best, as the black blemishes walnuts leave behind are unfazed by soap and water and other traditional cleaning methods.
Black walnuts can create quite a mess if they're left to lay in your yard or driveway. If left to lay, the evidence they leave behind takes a while to fade.
On the other hand, they can be quite useful when used to create a natural homemade wood stain. All the qualities that make black walnuts such a nuisance to landowners, make them ideal for staining wood. Plus, utilizing the hulls to make a stain is a great way to reduce waste if you're collecting walnuts to preserve and eat.
Farm and Dairy August 28, 2018