ART OF GLASSMAKIN6. ^7 



Whether this fusion would restore the glass to its former 

 transparency, and other characteristic properties. 



I took a piece of the glass No. 1 of Mr. Ciffle (p. 59), Experiment. 

 that is, window glass devit'itied without any cement, remain- 

 ing white, perfectly opake, and of extraordinary strength 

 notwithstanding its thinness. After having reduced it to 

 powder, I put 7 gr. [108 grs] into a platiua crucible with a 

 cover, and raised the fire to l6o° Wedg. The result was a 

 mass tolerably well fused, but white, inclining slightly tol 

 greenish, and having barely some appearance of being 

 translucid on the edges ; very smooth at the surface, but 

 beneath it full of little cavities occasioned by the ebullition. 

 There was a loss of weight of 59 mill. [0*9 of a gr.] oj- a lit- 

 tle more than 8 thousandths. 



It became an interesting inquiry, to find what change a Experimeui, 



refusion would produce in plate glass, in which the mutual "1'^*^ P^^^* 



- . . glass. 



saturation of the silex and its fluxes is commonly more accu- 

 rate ; and particularly whether in this also there would be a 

 diminution of weight. Into a platina crucible 1 put 62 gr. 

 t957'6 grs] of pulverized St.Gobin plate glass, and kept it 

 for 3t hours at a heat of 48° Wedg. The result was a mass 

 completely fused, the frizzled surface of which [surface 

 ratinee], to use the term of the glass-men, indicated a 

 slight commencement of devitrification*, which had a 

 yellowish tinge, and somewhat greater hardness than the 

 interior; alterations that Mr. d'Artigues had already ob- 

 served in glass, which, being more simple in its composi- 

 tion, and more perfectly combined, resists the continued * 

 action of heat much more. The great number of blebs, 

 that had formed in the lower part, did not allow me to de- 

 termine with accuracy its specific gravity ; but there was a 

 loss of weight of 2 dec. [3 grs], or a little more than 3 

 thousandths, without any circumstance of the process "•ivino- 

 room for the slightest suspicion, that it could have been oc-? 



♦ Tkis surface, examined with a lens, exhibits an immense quan> 

 tity of small fissures, forming by their intersections prisms with un- 

 equal sides. By causing the light to pass through the two opposite 

 fractures on the sides, rudimentsuf crystallization are perceptible be- 

 neath the superior crust, which jilso indicate the first effects of de- 

 vitrification. 



F 2 ca«ioned 



