Condensed Milk and Miek Powder 



77 



era'ily by milk condensing companies, lies in the fact that these sold- 

 erless seals are all patented. In most cases the inventors or patent 

 holders are condensed milk manufacturers. They refuse to sell their 

 patents at a reasonable price to other condenseries and they charge 

 exorbitant royalties for the use of their patents by their competitors. 

 With the possible exception of the "Sanitary can," solderless seals 

 are not as reliable as solder seals. 



Soldering Devices and Machinery. — The sealing of all solder- 

 less seals is done by specially constructed sealing machines. 



Fig. 29. Soldering stove 



Courtesy of Arthur Harris & Co. 



For seals with solder there are sev- 

 eral machines on the market but most of 

 this work is as yet done by hand. For 

 this, different types of soldering coppers 

 are in use and the copper tips are heated 

 in soldering stoves or pots. Some sold- 

 ering coppers have hollow circular tips 

 with a diameter equal to that of the cap 

 used. The hollow tip is telescoped by a 

 rod which holds the cap in place and the 

 periphery of the tip fits into the groove 

 of the opening of the can, where it melts 

 the solder, completing the seal. A rapid, 

 neat and leakless seal can be made with 

 this instrument. 



Ordinary soldering coppers with a blunt point, such as are in 

 general use by the tin smith, are not very satisfactory. Unless they 

 are drawn out and filed down into a fine point, their use is not con- 

 ducive of neat work, progress is comparatively slow and leakers are 

 often numerous. When gas is available the automatic soldering 



Fig. 30. A convenient device for 

 soldering by hand 



Courtesy of The Sprague Canning 

 Machinery Co. 



