This laboratory has often been faced with the problem of cleaning and polishing hard optical materials such as barium fluoride, calcium fluoride and lithium fluoride. The standard water techniques for polishing sodium chloride and potassium bromide (I) are not effective for the fluorides because of their low solubility in water. Other methods such as those used for polishing glass (2) are very time consuming. The increasing use of barium fluoride for water solution work in this laboratory made it particularly desirable to find a rapid, simple, manual method for polishing this material. It was found that by simply substituting concentrated HC1 for water during the polishing process, barium fluoride could be polished to a clarity and flatness comparable to that obtained by water polishing sodium chloride.
D. S. Erley, B. H. Blake, and A. W. Long, "Simple Technique for Polishing Barium Fluoride Windows," Appl. Spectrosc. 14, 25-26 (1960)