Method of polishing glass articles in an acid bath
OwnerErich Salzleinventor
Life of this patent
Estimating the term…
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.
Claims16
A method of polishing glass articles comprising
- providing a polishing bath of acids consisting essentially of (1) 35-75% by weight of bath of sulfuric acid, (2) 1.5-12% by weight of bath of hydrofluoric acid, and (3) an amount of at least one non-oxidizing organic acid which is stronger than HF sufficient to hinder the dissociation of HF and thereby retard the formation of fluoride ions in the bath;
- contacting glass articles to be polished with said polishing bath for a time sufficient to effect polishing of said glass, whereby deposits forming during polishing are in fine form with poor adhesive capacity on the glass surface;
- avoiding the substantial presence in the bath of fluorosilicic acid which serves to remove alkali metal ions in the form of precipitates of alkali metal silico-fluorides;
- and
- repeatedly contacting glass articles with said bath over a normal working shift of about 8 hours and, upon decrease in the effectiveness of said polishing bath or the appearance of polishing flaws due to reduction of bath effectiveness, adding to the bath 0.1 to 5 g of sodium chloride and/or potassium chloride per liter of polishing bath without otherwise renewing or cleansing said bath over said shift.
Dependencies are inferred from the claim text.