Impurities such as grease from fingers can ruin the integrity of a solder joint. Make sure that the components are clean at every stage of the soldering process; this also applies to the solder itself. Clean surfaces are required, as otherwise the solder will not be able to flow correctly via capillary action. If a piece of silver is fresh from the supplier it may be clean enough to solder with without cleaning, but otherwise it must be scrupulously cleaned. Careful cleaning will remove the surface contaminants which would otherwise act as a barrier to the solder. Oil and grease can be removed with a solvent; any actual dirt or tarnish must be removed mechanically with emery paper or needle files. Between soldering stages, the silver must be re-cleaned. This process can be made quicker by applying a barrier to oxidation such as Argotect during heating. Before another soldering stage is completed, any oxidation of the joint will have to be removed with pickle, emery paper or needle files.
