This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
To make old oak of ash, elm, box alder, chestnut, maple, yew, and sycamore wood use a solution of copper acetate, or iron acetate. Either of these can be made by allowing a strong acid to come in contact with copper or iron. Acetic acid, or vinegar, will do for the acid. The chemical can be obtained from a local druggist if it is not desired to make the stain. By varying the strength of the solution, several shades may be obtained. A weak solution of iron acetate gives various brown hues. As the strength of the salt increases by concentration, the shades of brown darken.