ENHANCING SILVER TARNISH-RESISTANCE

An alkanethiol, alkyl thioglycollate, dialkyl sulfide or dialkyl disulfide may be used to surface treat of an alloy of silver containing an amount of germanium that is effective to reduce firestain and/or tarnishing. The treatment has been found to further reduce tarnishing of the alloy such that a sample can be supported close above a 20% solution of ammonium polysulphide for at least 30 minutes while retaining a generally untarnished appearance. The treatment may be carried out at the end of manufacturing a shaped article to give rise to an article that will preserve its untarnished appearance both during transit to a point of sale but during subsequent display for an extended period. The invention therefore also includes a method for manufacturing a tarnish-resistant silver article, which comprises the steps of forming a shaped article of an alloy of silver containing an amount of germanium that is effective to reduce firestain and/or tarnishing, surface treating the article with an alkanethiol, alkyl thioglycollate, dialkyl sulphide or dialkyl disulphide; and introducing the article into packaging. Also disclosed for use in treating an alloy of silver as aforesaid is a water-based composition comprising a treatment agent selected from an alkanethiol, alkyl thioglycollate, dialkyl sulfide or dialkyl disulfide and a mixture of an anionic surfactant and an amphoteric or nonionic surfactant in a concentration that is effective to solubilise the treatment agent.