2. A strip of soft solder, price about three-halfpence.
3. Soldering fluid or flux. This can be made at home from a pennyworth of spirits of salt (from an oil shop). Put a little of the spirits into a separate bottle and drop a few scraps of zinc into it. When it has stopped "fizzing" it is ready for use.
4. A pennyworth of resin.
5. A piece of sheet tin.
Soldering is not nearly so difficult as people think. There is one thing really essential for its success, and that is unlimited patience in cleaning the metal surfaces to be joined together. Solder will not adhere to dirty metal. The surfaces must be thoroughly scraped and cleaned with an old knife, then filed, rubbed with emery-cloth and protected by a coating of flux. The flux required for use should be kept in a shallow dish (e.g. a meat-paste jar), to prevent it being upset; it can be put on with a small brush.
The copper bit of the soldering iron must be covered with a thin film of solder before any soldering is done; this is to ensure that it is perfectly free from dirt or dust. This process is called "tinning the bit." It is quite simple. Heat the iron to a dull red heat, not quite red hot, as the solder would otherwise be destroyed. Then quickly file the four faces of the point to remove any dirt or oxide that may have got on it and which would prevent the solder from sticking to the bit. Next dip the bit for a second or two in the soldering fluid and melt off a drop of solder on to the piece of sheet tin on which is put a little piece of resin. Turn the point of the bit round and round in the melted solder until it is completely coated. It is very important that the soldering iron should at no time be overheated, as this tinning would be burnt off; nor can it be repeated too often that the surfaces to be joined must be thoroughly cleaned; failure to do this is in most cases the cause of unsuccessful soldering.
Fig. 513
Fig. 514