 A more robust requirement on the subject matter of a patent is that the invention defined in the claim for patent protection must be new or novel. There are several categories or events, all defined by statute, that can anticipate and invalidate a claim of a patent (35 U.S.C. §101 (1988)). In general, the novelty requirement invalidates patent claims if the invention was publicly known before the patent applicant invented it. For example, someone could not obtain a patent on the production of stained glass by mixing potash and sand, heating the mixture to 3000 Fahrenheit, and then adding different metallic oxide powders to produce different colors, even if the inventor in this case independently came up with this process.  