A device similar to the hot box described is available commercially from
 
Better Way Wax Melters
116-11th St. S.E.
Altoona, Iowa  50009
(515) 967-4952
 
 
 
They have sizes for 15 frames and up.
 
I used it to melt a large number of brood frames I received from a beeekeeper.
It worked fine.  The frames could be scraped clean and reused.  However I felt
that new frames were worth the expense.
 
It also does a good job of melting cappings and queen excluders.
 
Good Luck