The appearance of walnut may be given to white woods, by painting or sponging them with a concentrated warm solution of permanganate of potassa. The effect is different on different kinds of timber, some becoming stained very rapidly, others requiring more time for this result. The permanganate is decomposed by the woody fibre; brown peroxyd of manganese is precipitated, which is afterward removed by washing with water. The wood, when dry, may be varnished, and will be found to resemble very closely the natural dark woods.