An extract from General Building Repairs (4th Edition) (? 1937)
Alfred G Geeson
Virtue & Co Ltd., Thavies Inn EC1
Plumber's solder - commonly called metal - is composed of 2 parts of lead to 1 part of tin, and tinman's or soft solder 2 parts tin to 1 of lead. It is necessary to thoroughly clean the euhface of the metal by scraping, filing, or rubbing with emery cloth, before soldering is commenced. Every particle of dirt or grease must be removed, and a flux applied to the cleaned surface, to cause the solder to adhere to the metal. Spirits of salts (hydrochloric acid) is commonly used as a flux for brass, copper, and zinc. It is first 'killed' by dropping in small pieces of zinc until effervescence ceases. Resin is frequently used for the purpose instead of spirit, on account of the possibility that damage may be caused to the article by the subsequent rusting action of the acid. Tallow or resin is employed on plumber's leadwork.
The pipes are first prepared by opening the end of one slightly with a turnpin, while the end of the other is trimmed off to a bevel with a rough file, so that it fits accurately into the expanded end of the first one with a bevelled seating. A band of soil is then painted all round the pipes for a distance of about 4 in., to prevent the metal from adhering where it is not wanted when the joint is wiped, after which each end is scraped clean for 2 in. And rubbed over with tallow to prevent oxidation oc the clean surface. Both pipes are then fitted together, and fixed securely by tying them tightly to iron spikes which are driven into the wall. This supports the pipes, and prevents them from moving while the joint is made.
Meanwhile, the metal is being heated in a cast-iron pot. The heat should be tested by plunging a piece of paper into the molten metal. If the paper ignites, the metal is too hot, but if the paper is just scorched, the temperature will be correct. When the metal is ready, a ladlefull is taken in one hand and a small wooden spatula or stick in the other, and the metal is gently flicked on to the joint with the stick, a little at a time. Some will adhere to the pipes, the rest falling onto a board which has been placed underneath to catch the waste. When the joint is well covered, the metal is carefully wiped and mended round the pipe with a cloth, until the whole mass becomes heated together, more metal being added until the joint has assumed a bulbous shape. If the metail cools so quickly that it becomes too solid to work with the cloth, it is heated again by holding a hot iron or a blow-lamp against it for a few moments, and then resuming the wiping. Some little practice is required before a really satisfactory job can be made, but if proper adhesion has been secured between the metal and the lead pipe, this will be the strongest and most effective joint that can be made.
In a blown joint, the ends of the two pipes are prepared as for a wiped joint, but instead of soiling the wipe and wiping a band of metal all round, only the narrow rim of the opened-out pipe is filled with solder, this being melted with a blow-pipe or a copper bit until it flows evenly round the rim. This joint is only suitable for unimportant jobs, as it has little strength.