=Prepared Gamboge.=—Crude gamboge cannot be used in oil painting because it never gives a uniform shade, but when the colouring matter is freed from admixtures and ground with oil, it gives a deep durable colour of great beauty. The colouring constituent of gamboge is a resin which is fairly soluble in strong alcohol, whilst the impurities are insoluble. The pure colouring matter is obtained without great expense in the following manner: Coarsely powdered gamboge is placed in a large flask with strong alcohol; the flask is well closed, placed in a warm position and repeatedly shaken; the deep yellow solution is carefully poured off from the sediment, water is then added, when the colouring matter separates in flocks. Only sufficient water should be added to precipitate all the colouring matter; test portions of the liquid should be examined from time to time, the alcohol can then be recovered by distillation and used again. The colouring matter separated from the alcoholic solution forms a hard mass on drying; it must be very finely powdered before it is ground in oil. There are many other yellow lakes which can be obtained by adding alum to an aqueous decoction of the colour-bearing material and neutralising the liquid. Such decoctions are obtained from fustic, quercitron (_Quercus tinctoria_), young fustic (_Rhus cotinus_), the root of barberry (_Berberis vulgaris_), annatto (the fruit of _Bixa orrellana_), turmeric (the root of _Curcuma longa_), etc. The yellow lakes obtained from these sources are seldom used in painting, the mineral pigments are preferred on account of their finer appearance. These colouring matters are largely used in dyeing to produce shades varying from yellow to brown, the majority are also used in calico printing. =Fustic Lake.=—Of the colouring materials mentioned above fustic produces a lake which is so handsome that it deserves larger use in painting than it has yet found. ”Old fustic” is chipped immediately before use and extracted with boiling water; whilst still hot the extract is mixed with a hot solution of alum; on cooling a fine yellow precipitate is formed, which when dry is frequently sold under the name of Dutch pink. (Genuine Dutch pink is made from a decoction of yellow berries; the majority of the pigments sold under this name are made from decoctions of mixtures of the different yellow dye wares.)