sed. Where there is no gas supply, the
most satisfactory is perhaps an oil stove. It is now possible to get
an odorless oil stove which gives a hot smokeless flame which is very
satisfactory. In the winter, if a coal stove is used to heat the shop,
the stove may also be used for heating the sealing compound, but it
will be more difficult to keep the temperature low enough to prevent
burning the compound.

(b) Pot or Kettle. An iron kettle is suitable for use in heating
compound. Special kettles, some of which are non-metallic, are on the
market, and may be obtained from the jobbers.

(c) An iron ladle should be obtained for dipping up compound, and for
pouring compound when sealing a battery. Figure 81 shows a convenient
form of ladle which has a pouring hole in the bottom. A taper pin,
which is raised by the extra handle allows a very fine stream of
compound to be poured.

The exact size of the ladle is not important, but one which is too
heavy to be held in one hand should not be used.

(d) Several old coffee pots are convenient, and save much time in
sealing batteries.

Sealing compound is a combination of heavy residues produced by the
fractional distillation of petroleum. It is not all alike-that
accepted for factory use and distribution to Service Stations must
usually conform to rigid specifications laid down by the testing
laboratories governing exact degrees of brittleness, elongation,
strength and melting point. For these qualities it is dependent upon
certain volatile oils which may be driven off from the compound if the
temperature of the molten mass is raised above the comparatively low
points where some of these oils begin to volatilize off as gaseous
vapor or smoke.

Compound from which certain of these valuable constituent oils have
been driven off or "burned out" through overheating is recognized
through too great BRITTLENESS and SHRINKAGE on cooling, causing
"CRACKED COMPOUND" with all of its attending difficulties.

[Fig. 81 Pouring ladle]

Do not put too much cold compound in the kettle to begin with. It is
not advisable to carry much more molten compound in the kettle at any
time than can easily be dipped out-cold compound may be added during
the day as needed. When there is considerable cold compound in the
kettle, and the heating flame is applied, the lower bottom part of
the mass next to the surface of the iron is brought to a melting point
first-heat must be conveyed from this alrea