In order to give tinplate a crystalline surface, polishing it by hammering and then heat over a coal fire, so that the tin will melt without oxidation, then remove same, and water is poured over the side which has been exposed to the fire, from a vessel so arranged that a broad stream can be focused on the surface. As it cools the tin crystallizes, but a poor appearance is presented by the surface and it is necessary, therefore, to give it further treatment with acid. Place the sheet in a compound of 2 parts hydrochloric acid, 1 part nitric acid, and 3 parts water. This will cause the dissolution of the tin upon the surface in a little while, then take the sheet out. wash it in caustic potash lye in order to enhance the metallic lustre, and rinse in water, dry at a moderate heat and then coat with transparent copal lacquer. If it is desired, the direction of crystallization may be determined by the surface manipulations; for instance, draw designs on the back of the heated and cooled plate, with a hot soldering iron and the tin will melt through the plate and the reaction of the design on the side can be made, owing to the action of the acid changing the direction of the crystallization. If tinned sheet-iron is heated over the flame of a spirit lamp the tin will fuse all around and a round spot will be formed, whose circumference will vary according to the time the sheet is held over the flame. When the flame is removed the place of its application will be recognized as a center of stellated crystallization. Pure tin is best for this purpose. The moire is, as a rule, obtained by the exposure of tin which is carefully cleaned, to the action of sulphuric acid, nitric acid or hydro-chloric acid, the surface covered with moire being finally freed, as much as possible, from the oxides produced during the continuance of the operation.