Cliff, Walnut hulls, that is the outer husk around the walnut nut is a very strong stain, just ask any of us older kids that used to gather and shuck walnuts. The stain is the strongest after the green hulls turn dark brown and start to rot off the nuts, the time for shucking. The hulls were gathered into a galvanized bucket and allowed to seep in water to cover, then set over a fire to boil down and concentrate. We used the stain like log wood to color traps for trapping. A number of re-enactors use the same stain to color cloth a nice "nut brown." I have used it to add color to walnut. It is basically a water based stain and thus will raise the grain of the wood you are working on. I have not tried it on maple, but my guess is that the result will be a rather light brown color. If you post a photo of your hands dyed a nice brown we will know that you have been shuckin walnuts. Ron