To darken mahogany, enclose the finished articles in an air-tight box, on the floor of which are placed a number of shallow dishes containing liquid ammonia .880 per cent. The fumes, which may play around for hours, have such a penetrating power that a thin shaving of the wood might be taken off without disturbing the colour; this treatment does not raise the grain. Stains may also be applied with a brush. Dissolve loz. of bichromate of potash in lpt. of water; two or three applications of this may be given, and, when the stain is dry, the colour may be enriched by wiping over with red oil, obtained by steeping 2oz. of alkanet root in 1/2pt. raw linseed oil. Common washing soda, carbonate of soda, or water in which lime has been slaked, will give different shades. A French method is to rub the surface with dilute nitric acid, which, when dry, may be brushed over with a solution of 1 1/2oz. dragon's blood and .', oz. carbonate of soda, dissolved in lpt. of methylated spirit.