To have a perfectly clean surface of the two gutta percha enlargements, remove all impurities by the way of peeling them with a sharp knife. Warm gently both knobs and the copper joint, and cover the whole length of the bare wire with compound, planing it with a warm smoothing-iron.
Draw then with the fingers one of the warmed and softened knobs carefully up to the other knob or enlargement, leaving on its way a perfect tube of gutta percha upon the wire, decreasing gradually to the thickness of the copper strand towards the other knob. Any superfluous gutta percha is removed. This scarf is finished with a warm smoothing-iron, so as to unite it to the compound on the wire strand, and a thin layer of compound is also put over the scarf in the same manner as before.
The other knob is then warmed and drawn in the same way over the tube already formed, which is at the same time heated sufficiently to make the two adhere.
Apply a layer of compound on the second scarf of gutta percha, covering it in the same manner as described for coating the bare conductor, and cover it with a small sheet of gutta percha in the same manner as described above, so as to make the finished joint to the size of the core as manufactured.
Rules to be observed in forming Joints.—The following rules must be carefully observed in forming either a temporary or permanent joint:—
1.—In laying bare the conductor, the dielectric should be warmed and then pulled off, so preventing any chance of it being damaged, which might be the case were the dielectric to be cut off.
2.—For a perfect junction, soldering is necessary.
3.—The wires before connection should be carefully cleaned, and the hands of those performing the work must be dry.
4.—Gutta percha should not be given too much heat, for it then becomes oily and will not, in that state, properly adhere.