This section is from the book "Soldering For Workshop, Farm And Home", by John Bonert. Also available from Amazon: Soldering For Workshop, Farm And Home - Information On Soft And Hard Soldering - Projects For The Workshop Explained And Illustrated.
Tinning can be done with a solder pot and ladle. The solder is melted in a solder pot to a moderate temperature. This temperature is best tested with a thin pine stick or a piece of paper folded several times to stiffen it enough so it can be dipped below the surface of the molten solder. One very important safety measure when testing the solder for heat is never to dip a ladle, paper or stick into the solder unless it is perfectly dry. The least moisture dipped under the surface of the molten solder will make steam immediately and cause an explosion which will spatter solder into the air. The violence of such an explosion is governed by the amount of moisture introduced. The more the moisture the more the solder will spatter about. A hot solder pot may be left in the rain without any danger as the drops will hit the surface and either evaporate at once or lie on the surface and sizzle. But as soon as the water gets below the surface it makes steam and causes this spattering. A cold ladle dipped into the solder will also cause this spattering. The ladle should be heated before dipping it into the solder. When testing the solder with paper the end that is held in the hand should be folded over so that there is no passage through the paper. If this is not done some solder may pass through the folds of the paper and burn the hand. The stick or paper is dipped into the solder and withdrawn quickly. If the paper is slightly brown after dipping, the solder is hot enough. If it is charred black it is too hot and if the solder is very hot the paper will burst into flame. The objects to be tinned are cleaned and fluxed and then they are slowly dipped into the hot solder. When they are withdrawn the surface will be perfectly tinned if the cleaning was properly done. This method is used by plumbers for tinning brass ferrules and nipples which are to be joined to lead pipe by wiping. Brass is easily tinned in this way but as brass is a composition of copper and zinc, if the solder is too hot some of the zinc may be released and the surface will not tin. The hot solder will turn the cleaned surface black and the cleaning will have to be done over again. Under the subject "Soldering Coppers" will be found a drawing of a small solder pot attachment for an electric copper. The soldering tip is removed and the pot attachment is screwed into its place. This is used where a large number of twisted ends of wire called "pig tails" are to be soldered by dipping. Tinning by pouring is done by holding the work over the solder pot and with a ladle pouring the hot solder over the surface allowing the solder to run back into the pot.