786 Transactions of the American Institute. 



to these five boilers ; but we consider them as very good specimens 

 of boilers. 



Adjourned. 



February 9, 1872. 



Prof. S. D. Tillman in the chair; Robert Weir, Esq., Secretary. 



The meeting was opened by the reading of the following paper by 

 Mr. "W. E. Partridge, who also exhibited samples to illustrate the sub- 

 ject treated of. 



Protecting Plates or Design Plates as Applied to Enameled 



Glass. 



For want of a better name, this paper might be announced as upon 

 " Stencil Plates, their connection with Stained Glass work, etc. ;" but 

 the plates which I shall exhibit to you this evening are not, in any 

 sense of the word, stencil plates. The technical name, though little 

 used, is " formulas." The only resemblance which they have to sten- 

 cils is in being cut from thin sheets of metal. "Webster defines a 

 stencil thus : " A thin plate of metal, leather or other material used 

 in painting, marking, etc. The pattern is cut out of the plate, which 

 is thin, laid flat on the surface to be marked, and the color brushed 

 over it." Now the pattern in these plates is not cut out, and the color 

 is never brushed over them. To nearly perpetrate a bull, one may say 

 that the plate is cut out and the pattern remains, which is exactly the 

 case. In no case is the color ever brushed over the plate. 



In the ornamentation of glass by enameling, the first thing to be 

 done is to clean the glass perfectly ; and so thoroughly is this done, 

 that when the glass is ready for the color it approximates to what a 

 chemist would call clean. The colors used in glass work are minerals, 

 oxides of the metals, and other substances capable of bearing a great 

 •degree of heat. 



Indeed, in the majority of cases, the color does not appear until the 

 glass has been heated to redness. The colors are mixed with various 

 proportions of flint glass and other materials termed fluxes. These 

 are then ground exceedingly fine. They are then mixed with gums 

 or oils, so that they can be readily applied to the surface of the glass. 

 The next operation is termed " laying the ground," which consists in 

 giving the glass a perfectly even coating of the enamel over its whole 

 surface. This is done by applying the colors technically called 

 "enamels" to the glass by means of broad soft brushes; and then, 



