Long storage time and lack of adequate surface protection sometimes give rise to less than ideal soldering conditions. Heavier than normal oxidation of Copper surfaces on PWB's create situations whereby, the usual fluxing and soldering processes alone become ineffective in obtaining a well soldered assembly. It is on occasions such as these that more aggressive cleaning methods must be employed. In an attempt to produce solderable surfaces from these severely oxidised, unsolderable ones, printed circuit manufacturers, in their haste occasionally choose the wrong cleaning methods for their needs.