How much salt makes a brine appears to vary according to whose recipe you look at. The well known Alton Brown brine recipe:
For the brine:
- 1 cup kosher salt
- 1/2 cup light brown sugar
- 1 gallon vegetable stock
- 1 tablespoon black peppercorns
- 1/2 tablespoon allspice berries
- 1/2 tablespoon candied ginger
- 1 gallon iced water
This works out to a half cup per gallon of liquid. If you use veggie base to make the veggie stock, there is added salt there.
The link Jenny provided mentions the significant differences in types of salt. For example, if Alix's cookbook quotes 1/2 cup per gallon using table salt, that would be roughly equal to a cup of Diamond Crystal Kosher salt per gallon. So maybye Alix's and Jennyema's recipes are closer than you would think at first.