In order that solder employed for soldering copper may have the same color, the first step in preparation is making a saturated solution of pure sulphate of copper and the application of the same to the solder. When the solder is touched with an iron or steel wire it becomes colored with a copper film which may be augmented at pleasure by repeated dampening with the solution of copper and touching with the wire. If it is desired that the soldering should show a yellow color, 2 parts of solution of sulphate of copper should be compounded with 1 part of saturated solution of sulphate of zinc, the mixture applied to the coppered place and all rubbed with a zinc rod. Should it be desired to gild the soldered place, copper it in accordance with the above description and coat with a solution of isinglass or gum and scatter bronze powder over it. This forms a surface which can be polished when the gum is dried.
(2) When brass is soldered with soft solder, the difference in color is so marked as to direct attention to the spot mended. The following is the method of coloring soft solder: First prepare a saturated solution of sulphate of copper (bluestone) in water, and apply some of this on the end of a stock to the solder. On touching it with a steel or iron wire it becomes coppered, and by repeating the experiment the deposit of copper may be made thicker and darker. To give the solder a yellowish color, mix one part of a saturated solution of sulphate of copper, apply this to the coppered spot, and rub it with a zinc rod. The color can be still further improved by applying gilt powder and polishing.
On gold jewelry, or colored gold, the solder is first coppered as above, then a thin coat of gum or isinglass solution is applied and bronze powder dusted over it. which can be polished after the gum is dry, and made very smooth and brilliant; or the article may be electro-plated with gold, and then it will all have the same color.
On silverware the coppered spots of solder are rubbed with silvering powder, or polished with the brush and then carefully scratched with the scratch brush, then finally polished.