Two pieces of metal to be soldered together must be filed or scraped to a clean metallic surface if not already bright. They are brought into the position in which they are to be soldered and firmly held together. The joint is sprinkled or swabbed with flux to remove grease and prevent the formation of oxide. Holding a bar of solder in one hand and a heated soldering copper in the other, the operator brings the copper against the bar, melting a slight amount of solder which either drips on the joint or sticks to the point of the copper by which it is wiped and spread over the joint. The two parts to be joined must be heated by the copper to the fusion point of the solder in order to make the molten solder stick to them.

A stronger joint may be made by first carefully tinning the surfaces joined in soldering.

The end of a soldering copper must be kept filed to a smooth point and this point is tinned with solder by rubbing it on a stick of solder. In heating the copper for use, it should not be heated enough to melt the solder from the point.

Soldering coppers heated by the electric current from an ordinary lamp socket are very convenient, dispensing with the use of the fire-pot.

Soldering fluxes remove grease and dirt, and assist in reducing or fusing the film of oxide covering the work. The usual fluxes are rosin, sal ammoniac, zinc chloride, and borax.