=True Charcoal Black.=—In charcoal-burning wood is burned in great piles with restricted air supply; the greater part of the carbon contained in the wood remains behind as charcoal, which is used for fuel. The charcoal made from hard wood, such as maple or beech, is not well suited for pigments; the lighter and more porous the wood, the more pure is generally the shade of the charcoal, and the more easily it can be ground. When, therefore, charcoal is to be used as a pigment it should be made from wood of a porous nature; the wood of the lime, black-alder and spindle tree is particularly adapted for this purpose. Spent tan-bark is a very cheap, and at the same time suitable material for this purpose. It generally consists of oak bark, and has lost the greater part of the salts it contained by long contact with water; also the woody substance of the bark has suffered a change which is favourable to carbonisation. This is especially the case when the bark has been stored for some time; a considerable quantity of the humins previously mentioned has formed in it, and these are easily decomposed at a low temperature. The charcoal, however obtained, is ground to a soft powder. When it has reached the proper degree of fineness it should be repeatedly washed with water to remove the salts. When instead of pure water a very dilute acid, such as hydrochloric, is used, practically all the salts dissolve, and the residue consists of nearly pure carbon. =Vine Black.=—In wine-producing countries a good and cheap black can be made from the residues of the wine manufacture; this is the so-called vine black. Either the pressed grapes or the lees separated in the fermenting vessels may be used. _Vine Black from Wine Lees._—The lees always contain a considerable quantity of liquid, they must be thoroughly dried before they are carbonised; this is most simply done by spreading out the pasty mass in a thin layer, and exposing it to a temperature of about 100° to 120° C. In drying the volume considerably diminishes. The lees are changed into a brown mass which is easily powdered; it is packed into barrels while still warm, and can be kept for a considerable time without alteration. Fresh lees can be kept but a short time; they are quickly destroyed by a rapid fermentation.