PLATED QUARTZ CRYSTAL UNITS 



241 



the stylus. The rounded stylus also results in a more uniform distribution 

 of the material. The material is applied to the end of the stylus by spread- 

 ing a small amount of the paste on a glass plate from which it is transferred 

 to the stylus and then deposited on the crystal. The material on the glass 

 plate should be wiped off and replaced quite often due to settling and drying 

 out of the mixture, in order to insure uniformly good spots. Generally 

 speaking, anywhere from two to six spots at the most should be possible 

 from one loading of the transfer plate depending upon the speed of the 

 operator. 



Regarding the character of the crystal surface, aside from cleanUness, and 

 its effect on the ultimate strength of adhesion of the silver spot, experience 



ppiyi.ig aliVCf SpjLS. 



so far with all the various cuts of plates does not indicate that this is a 

 factor. Spots have been found to adhere to poUshed surfaces as well as 

 ground and etched surfaces with about the same degree of strength. 



13.412 Firing oj Silver Spots 



Following the appUcation of the paste to the plates it is desirable to pre- 

 dry the spots in order to remove the low volatile constituents of the vehicle 

 prior to firing at high temperature. This may be done in a ventilated oven 

 or over a hot plate at approximately 300°F for about 15 minutes. The 

 plates are then placed in a furnace and heated up to between 975 to 1010°F 

 and held at that temperature for a sufficient length of time to obtain good 

 fusion of the spot to the plate. Ordinarily this reaction takes only a few 

 minutes after the plate has reached the proper temperature. After firing, 

 the plates are allowed to cool in the furnace to the point where they can be 



