For tinning any metal it is first necessary to clean it from dirt and sand and remove the surface which is oxidised or tarnished. This surface is removed by pickling the metals for a few hours in clean water containing a small quantity of sulphuric acid. The metals are then dipped in chloride of zinc, and afterwards laid in a bath of molten tin, out of which they are taken and held up for the surplus tin to drain off. It is doubtful whether this process is entirely satisfactory for artificial mineral waters, as the so-called tinned surface partakes more of the nature of an alloy of tin and zinc. Unless the proper appliances are at hand, it is cheaper and better to buy the coppsr pipes already tinned. It is also probable that white-metal cocks or taps would answer equally as well as those made of brass, which would have to be tinned before being ground in.