Dry Powdered Tannin
Powdered Tannic Acid, a commercial form of tannin, is not a true acid
but an acid-like substance called a polyphenol.
It occurs naturally in tea, coffee, oak, sumac bark and myrobalan.
Tannic Acid is a basic ingredient in the chemical staining of wood.
The tannic acid or tannin is already contained in woods like
Cherry, Oak, Walnut, and Mahogany.
Tannic acid can be applied to woods low in tannin so chemical stains
that require a tannin content will react. Potassium Dichromate,
and Ammonia, react with tannin to yield rich wood tones.
"Rust Water"(steel wool saoked in vinegar) applied to a tannin treated wood will yield rich Black tones.