PROCEEDINGS 



OF THE 



PHILOSOPHICAL SOCIETY OF GLASGOW. 



AFBIIi 18, 186 0. 



Dr. Anderson, the President, in the Chair. 



On a New Process of Ornamenting Glass. By Mr. James Napieb, 

 Chemist. 

 So early as 1670 it was observed, that when the mineral fluor spar 

 and sulphuric acid were mixed in a glass vessel, the glass was corroded, 

 and also that the fumes given off by this mixture produced the same 

 effect ; but it was not till a century after that the cause of this action 

 upon glass was explained by Scheele, who referred it to the disengage- 

 ment of an acid from the fluor spar, which he termed fluoric acid ; and 

 it was not till forty years after Scheele, that the true composition of 

 that acid was known. It was then found to be a compound of the 

 two elements, hydrogen and fluorine, and consequently was named 

 hydrofluoric acid. The peculiar difliculty attending the investigation 

 of this compound is its strong afiinity for almost all articles used in 

 these operations. It can only be kept in vessels of gold, silver, plati- 

 num, lead, or gutta percha. Its attraction for silica, with which it 

 forms a soluble compound, renders glass quite soluble in this acid. 



When the nature and properties of hydrofluoric acid were known, 

 the idea of etching upon glass with it was a natural one, and many 

 attempts were made to bring this application into use for printing from. 

 The mode of etching upon glass was similar to that of etching upon 

 metals, namely, by covering the surface of the glass with some unctuous 

 or resinous matter, capable of resisting altogether, or for a time, the 

 action of the acid. The pattern or figure required was then made upon 

 this resist, and with a suitable instrument the resinous coating was cut 

 through to the glass. On this being done the glass was submitted to 

 the acid fumes, given off by mixing ground fluor spar and sulphuric 

 acid together in a leaden vessel, and exposing to a gentle heat for a 

 short time. Those parts of the glass exposed by means of the graver 

 were acted upon by the acid fumes ; and after removing the whole 

 resinous coating from the glass, the figure or pattern was found etched 

 into the glass. 



Vol. IV.— No. 10. 2 y 



