Condensed Milk and Milk Powder 



79 



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 B.S 





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make an uneven seal, waste much 

 solder, and have many "leakers." This 

 is largely due to their ignorance of the 

 proper soldering temperature of the 

 coppers. An experienced sealer will 

 use from two to three pounds of 

 solder per thousand tin cans with 

 moderate-sized openings. He will seal 

 from fifteen hundred to twenty-five 

 hundred cans per day. 



Soldering Flux. — The use of 

 solder requires the application- of 

 soldering flux, to prepare the surface 

 of the tin for the solder. The flux 

 always precedes the solder. When 

 the hot solder is applied, some of the 

 flux is bound to sweat through, be- 

 tween cap and can, gaining access to 

 the interior of the can. The common 

 practice of using zinc chloride or other 

 similar acid fluxes, which are highly 

 poisonous, therefore, cannot be too 

 strongly condemned. Their presence 

 in the can may jeopardize the health 

 and life of the consumer, as well as 

 the marketable properties of the prod- 

 uct. There are other fluxes which 

 are absolutely harmless, and which, if 

 properly used, give satisfactory re- 

 sults. Dry, powdered resin, or resin 

 dissolved in alcohol or gasoline, are of 

 this class. Ammonium chloride, while 

 used in most tin shops, is not as well 

 suited 'for this purpose. 



Gas Supply. — A plentiful and 

 steady supply of gas is very essen- 

 tial. Where natural gas or gas from 

 a municipal corporation is not avail- 



