The Method of Silver-soldering.
—In hard-soldering with silver solder, first file or scrape the parts bright, and cover them and the solder with the borax paste. Heat gently at first so as to harden the borax; then continue to heat by blowpipe until a red heat is reached, at which the solder will run. The secret is to blow continuously until the solder runs, and not to stop half-way.
For soldering a silver watch case, an ordinary easy-running silver solder, which melts at a lower heat than silver, will do. But to make sure, shred the solder into very thin strips, and apply plenty of borax to them as well as to the joint to be united. Use the blowpipe gently at first so as to bake the borax, then heat the case all over almost to the melting point of the solder, and direct the flame to the part to be soldered until the solder runs and glistens. Cease blowing instantly, and plunge the case into a solution of sulphuric acid 1 part and water 10 parts, to whiten it; then wash in hot water and dry in sawdust. Be careful to remove all steel springs before soldering the case.
Soldering Small Work with Paillons.
—These are small squares, say, 1⁄8 in., of sheet silver solder, made by using the snips as in [Fig. 61], and prepared by well covering with the borax paste. Each paillon is placed in position with the tip of the brush, this job requiring a little practice. The solder should be clean, and if not, should be made so by passing through the fire and pickling. The work with the paillons in position should be slowly heated by blowing the gas jet on a part of the job farthest away from the solder; the borax will dry, and should the solder have moved, replace it with a suitable tool or the point of the wet camel-hair brush. The heat must not be applied too suddenly at first, otherwise the borax will boil up and push off the pieces of solder. The heat may be increased when the bubbling has ceased. Do not hold the work too far away, or it will get dirty in the smoke of the flame, or yet too near, else the gas will not be used to advantage. As the work begins to get hot, slowly work the flame towards the joint until the solder melts and runs into the joint. Give it now a little extra heat to get the solder thoroughly down into the crevices, and then let the work cool down. When nearly cold twist off the iron binding wire and put the job into the pickle. Leave the work in the pickle about ten minutes, when all the borax will be dissolved.
Fig. 59.—Section through
Pipes prepared for Silver-soldering
Fig. 60.—Pipes prepared for
Silver-soldering
