Abstract: The present invention relates to a process for the reduction and control of the concentration of hexafluorosilicate ions formed during the polishing of glass articles in a polishing bath containing sulfuric acid and hydrofluoric acid, wherein potassium fluoride, potassium sulfate, sodium fluoride, sodium sulfate or aluminium sulfate is added to the polishing bath or the sulfuric acid washing bath in a quantity such that a drop in the concentration of fluoride ions below the optimum operating range is avoided.

Abstract: A method is described for reducing the lead and/or barium emission of articles of crystal glass containing lead and/or barium, particularly so-called lead crystal and baryte glasses, on contact with a liquid phase, particularly aqueous, aqueous-acidic, alcoholic and aqueous-alcoholic liquids such as acetic acid solutions, wine, whiskey, liqueurs and the like, with the crystal glass objects being treated, if applicable before and/or after acid polishing, with 5 to 45% by weight of an alkali hydroxide solution at a temperature of 20.degree. to 60.degree. C.

Abstract: The method according to the invention of polishing glass in a polishing bath containing sulfuric acid and hydrofluoric acid permits long polishing times and thus reduced alternating treatments in polishing bath and washing bath at high polishing speed due to the fact that the polishing bath contains at least one acid which is stronger than the hydrofluoric acid, in particular acids whose dissociation constants are higher than that of the second dissociation stage of the sulfuric acid; preferably, oxalic acid is used. In order that the sulfuric acid concentration can be increased--in particular for glasses containing alkaline earth--0.1 to 5 g sodium chloride and/or potassium chloride per liter of polishing bath are added to the polishing bath during an 8-hour shift, either all at once or in portions.

Abstract: The invention relates to a polishing method for pressed glass or ground glass articles. As is conventional, polishing is effected in a bath containing sulfuric acid and hydrofluoric acid. Rinsing with a sulfuric acid and/or water washing bath intervenes and follows the polishing process. According to the method of the invention, the sodium and/or potassium ions resulting from the dissolution of glass constituents are removed from the polishing bath by the following means:(a) by adding fluorosilicic acid to the polishing bath, precipitating the corresponding silicofluorides and filtering off the solid matter,(b) by electrolysis in a mercury cell with the formation of sodium- and/or potassium amalgam,(c) by electrolysis in a cell having a cation semi-permeable membrane or(d) with the aid of cation exchangers.