SOME CERAMIC MANUFACTURING DEVELOPMENTS 267 



marked improvement in quality and reduced the cost of parts. The 

 method of automatic pressing developed constituted a major con- 

 tribution to existing commercial methods of manufacturing small 

 porcelain parts. 



Vitreous Enameled Copper Base Number Plates 



Manufacture of parts similar to the vitreous enameled number 

 plates used on calling dials and shown in Fig. 5 was limited to producers 



Fig. 5 — Copper base number plate. 



of enameled parts of the watch dial type. Because of our unusual 

 requirements for dimensions and character location together with the 

 need for a collar and locating pins, only one source of supply could be 

 developed. With rapidly increasing schedules for calling dials and 

 because of the possibility of conditions deyond the control of the 

 supplier interfering with the continuity of supply, this situation was 

 unsatisfactory and made it advisable to undertake manufacture to 

 remove possibilities of any embarrassment from a supply standpoint. 

 As sources of supply for copper enamels were also limited, various 

 enamel compositions were investigated. It was found that the fol- 

 lowing composition would give an enamel satisfactory for color, 

 texture, gloss, fusibility, and durability when fired on copper blanks: 



