The present invention relates to an improved tarnish remover. More particularly this invention relates to a tarnish remover/metal polish containing as essential ingredients a metal iodide such as potassium iodide, an acid, and water. The tarnish removers/metal polishes of this invention are effective, safe, and low in cost.
In the prior art many formulations have been proposed for removing tarnish and oxides from silver, copper, brass, and other metals. "Tarnish," as the term is used herein, embraces a film discoloration of the metal surface which occurs as a result of a chemical change in the metal as opposed to a mere physical soiling. An example is the formation of a sulfide or oxide film which is from all indications integral with the metal surface and similar to metal corrosion. The prior art formulations which have been proposed have been designed to either only remove the tarnish, etc., or to remove the tarnish, etc., and additionally repress the tendency of metal surfaces to re-tarnish or stain upon exposure to ordinary atmospheric conditions, thereby eliminating at least partially a periodic, time-consuming cleaning problem and to prevent a deterioration of the metal surfaces.
The prior art tarnish removers or metal polishes designed primarily to remove tarnish and stain conventionally comprise an abrasive material and a carrier such as water, a hydrocarbon solvent, or glycerine, either with or without a soap or an emulsified agent. Tarnish removers and metal polishes designed to repress tarnish and stain have included a film-forming material in the compositions such as waxes and resins so as to leave behind a thin coating, and in addition the use of anti-tarnish components such as a mercaptan or thiourea for the prevention of retarnishing. Exemplary prior art tarnish removers or metal polishes include the compositions described in U.S. Pat. No. 2,628,199 which utilize thiourea in an acidic dip-type silver and copper cleaning composition; U.S. Pat. No. 2,691,593 which discloses silver cleaning compositions in paste or liquid form containing abrasives, an emulsifying agent, a hydrocarbon carrier and, if desired, a mercaptan or thiourea; and U.S. Pat. No. 2,841,501 which discloses a silver polish containing a mild abrasive and a long chain alkyl mercaptan as an anti-tarnishing agent. The mercaptan apparently forms a thin protective film upon the silver and prevents retarnishing.
The aforesaid silver and copper cleaners and polishes are useful and have met with substantial approval. However, each has disadvantages and limitations. It has been found that certain of the acidic dip type formulations have a deleterious effect upon silverware, possibly resulting in more rapid retarnishing after the silver is again exposed to normal use and possibly causing removal of the silver surface. The compositions apparently function primarily as a cleaner and provide little or no protective coating. On the other hand, polishing compositions of the type described in U.S. Pat. No. 2,691,593, because of the hydrophobic carrier employed, are relatively difficult to wash off the silver after polishing. There is also an indication that the silver tarnishes more easily after initial cleaning. The rapid retarnishing may be a result of more exposed silver surface due to scratches on the silverware. Some polish-type formulations are believed to remove some of the metal surface when used. Additionally, a number of the prior art polishes or tarnish removers containing chemicals, such as thiourea, have toxic characteristics, some suspected to be carcinogenic, and for that reason are not well received.