The problem with 'salt box' is the equal distribution of cure among the other ingredients. In a small batch, 1 - 1½ lbs, you can manually and vigorously shake your mixture to produce a good mix of ingredient and evenly distribute the cure proportionately. However, in a large container of 10 - 30 lbs. of curing mixture, the different densities of ingredients settle at different rates and upset the amalgamation of cure, causing uneven curing results - too much on one part and not enough on the other, and to effectively mix it correctly involved a shaking system akin to a paint shaker or a rotating drum of large proportions, too big for 'small time' producers. My dad originally tried such systems and found the same problems with large scale dry-curing methods and larger items, such as hams, would not cure through correctly, causing uncured spots because of unequal cure distribution. He went on to explore wet-curing methods with injection and it produced a much better cure cycle with much better results (at first he tried several batches without injection and had the same results with sour bone; then found the Morton's injection Needle system and tried that. At one time I still had his injection needle, but lost it in a move (think my brother stole it, actually). Then, standardization of processing and finding the right method and doing it over and over again produced quality and consistent results.