Page 60 - Barbecue Chicken Made Easy

When salt is added to a solution, like a piece of chicken which is about 75% water, the salt diffuses or spreads out and seeks equilibrium. Osmosis is when the water moves into salty places through semi-permeable membranes in an attempt to achieve equilibrium.
The problem with wet brining poultry is that it can make the skin soggy and harder to crisp. That's why wet brining works best on boneless, skinless breasts—food that cooks so quickly that the absorbed moisture doesn’t have time to drip out. Chicken thighs, on the other hand, are moist enough from fat that they really don’t need wet brines. If you do decide to wet-brine, the brine should contain 5 to 10% salt by weight. Here's a simple formula.
Add one cup of hot water to a two-cup measuring cup. Then pour
in salt, any salt, until the water line reaches 1 1⁄2 cups. That will be
about 1/2 pound of salt by weight. Stir to dissolve then dump the
solution into 1 gallon of cold water. This recipe results in a 6.4%
brine regardless of the grain size of the salt.
How do we know? Because a unit of salt by weight delivers the same salinity regardless of the grain size. A unit of salt by volume delivers different salinity because large grains have more air between them. In this recipe, the water infiltrates the voids between the grains of salt, compensating for the lower density.
Making brines is also easy with metric weight measurements, which are simple to scale up or down. Since 1 liter water = 1000 grams:
6% brine = 1 liter water with 60 grams any salt 5% brine = 1 liter water with 50 grams any salt 4% brine = 1 liter water with 40 grams any salt