Tea contains tannic acid which darkens where it penetrates. Fiddle is alternate harder and softer parallel areas. The softer wood takes the tannic acid darkening MUCH more than the harder areas. Use of the tannic acid accentuates the difference in color between the harder and softer areas. It creates a great depth that is quite beautiful.
For walnut, except for very light colored walnut. I mix 50-50 household ammonia with very strong tea (maybe 5 bags per cup). After final sanding, I wipe the wet combination on the wood and let dry. The color is only on the surface so no whiskering is done afterwards. Using steel wool in the finish process takes care of this in any event.
There is a better method for light colored woods. For this you use the strong tea as before, wiping it on alone. Then you fume the wood with COMMERCIAL ammonia which is about 28%. You place the ammonia in an open container like a tuna fish tin. You do this in a wood, plastic, or cardboard enclosed container. You do NOT do this indoors as the very strong ammonia will setcha free and git ya divorced! Use a glass or plastic window to check for desired color. With maple, it might take several hours. This stronger method will turn black walnut absolutely BLACK in short order. The technique results in the best finish I have ever seen on maple.
