_Material:_ 1. Borax: bought in lumps, wrapped in tin foil, or
pulverized.
[Illustration]
2. Borax slate: a square piece of slate with a small depression in one
side. Any piece of clean slate will do. This is used to grind the lump
borax, or to mix the pulverized borax to a pasty condition on.
3. Solder: silver solder, sometimes called hard solder. It can be
bought by the sheet in large or small quantities. Bunsen burner, or
either one of the following: blowpipe and foot bellows with gas flame,
a blacksmiths' fire with coke or charcoal.
_Directions:_ The parts of the metals to be joined should, first of
all, be scraped or filed bright. This prepares them best for the
solder. Take a lump of borax, grind it up and mix with a little
water, on the slate, until it is like a paste. Take a sheet of silver
solder, cut a number of slits lengthwise down the sheet and then
cut them crosswise. You will have a number of pieces about 1/16 in.
square. These bits are dropped into the borax solution until they are
completely covered with the paste. With a camels' hair brush, wash the
edges of the metal to be joined, with the solution of the borax. Tie
the pieces together with an iron binding wire, taking care to have the
edges to be joined close together and in the proper position. If you
don't, the solder will not fill up all the openings and cracks, and
parts will be left unsoldered. Now, wash all around the joint with the
borax solution. Place bits of solder at intervals along the joint,
fairly close. Warm the work gently in the flame. This drives off the
water in the borax solution. When the borax is quite dry in the joint
direct a stronger flame over the whole work. Heat it gradually, but
be careful that no part of the metal, except that around the joint,
becomes red-hot, and that both sides of the joint get red-hot at the
same time. If you don't guard this, the solder will climb to the hotter
side and leave the other, and the edges will not unite. Cool it off in
water and file the joint perfectly smooth.