and then
pour in the muriatic acid. The acid will at once act on the zinc.
The fumes should be allowed to escape into the outer air. When
chemical action ceases, the liquid remaining is called reduced
acid.

PLUMBERS' SOILS AND PASTE

It is necessary when soldering or wiping a joint to cover the parts
of pipe adjoining the portion that is to be soldered or wiped so
that the solder will not stick to it. There are a number of
preparations for this. The one used by the best mechanics today is
paste, made as follows:

8 teaspoons of flour.
1 teaspoon of salt.
1 teaspoon of sugar.
Mix with water and boil down to a thick paste.

The advantages of paste as a soil are many:

_First_, it is made of materials easily obtained.

_Second_, solder will not stick to it.

_Third_, if pipe is thoroughly cleaned, the paste will not rub
off easily.

_Fourth_, poor workmanship cannot be covered up.

_Fifth_, when the work is completed, a wet cloth will wipe it
off and leave the work clean.

Another soil used is _lampblack_ and _glue_. A quantity of glue is
melted and then lampblack is added. This needs to be heated and
water added each time it is used. This soil is put on pipes with a
short stubby brush. The work when completed with the silvery joint
and jet black borders appears to the uninitiated very artistic and
neat, but when the black soil is worn away the uneven edges of the
joint appear, disclosing the reason for using a black soil that
covers all defects. The mechanic of today who takes pride in his
ability for good workmanship will not cover his work with black
soil.

It can readily be seen that the use of lampblack soil encourages
poor workmanship, while the use of paste forces, to a certain
extent, good workmanship on the part of the mechanic.

Before soil or paste is applied, the pipe needs to be cleansed.
Grease and dirt accumulate on the pipe. The methods employed to
remove all foreign matter are simply to scrape the surface with
fine sand or emery paper; sand and water will also answer for this
purpose. This cleans the surface and allows the soil or paste to
stick to the pipe.

MAKING DIFFERENT SOLDER JOINTS

The tools used in making the different solder joints as described
and illustrated in this chapter are shown in Fig. 14.

CUP JOINT.--The materials necessary for the work (Fig. 15): 12
inches of 1/2-inch AA lead pipe, paste, rosin, 1/2 an