Process for preventing heavy metal migration in crystal articles
AssigneeLalique
InventorPaul Cordie
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Abstract
Crystal articles are treated at high temperature by a gas produced by the vaporization of sulfate(s) of ammonium and of aluminum or of iron. For example, a temperature of 480.degree. C. is maintained for 15 minutes to 3 hours. After the article has cooled, the initial purity of the treated surface can be restored simply by washing the treated surface with water or soapy water. The process is carried into practice by placing the treatment powder 4 at the bottom of the article 1 to be treated and closing the opening 2 of the article 1 by means of a graphite plate 5. A device 8 holds the plate 5 in the opening 2. The invention provides a means of limiting the migration of heavy metals, such as lead, for articles made from crystal.
Claims7
A process for the surface treatment of crystal articles to prevent heavy metal migration comprising contacting the surface of the crystal article with a reactive gas produced by vaporization of a metal sulfate selected from the group consisting of ammonium aluminum sulfates, mixtures of ammonium sulfate and aluminum sulfate, ammonium iron sulfates and mixtures of ammonium sulfate and iron sulfates and hydrates thereof at an elevated temperature not greater than the softening temperature of the crystal, cooling the crystal article and water washing the crystal surface to remove any residual powder.
Dependencies are inferred from the claim text.