Salting brine for hard cheeses
Many cheeses — gouda, parmesan, mozzarella, Swiss, brick — are salted by floating them in a strong brine. The University of Wisconsin's Center for Dairy Research recommends salt at 21–23% of the brine by weight, just under saturation (about 26%). Below 16%, salt uptake slows and the brine gives less protection against microbes; much stronger, and the rind can case-harden.
For example, a 23% brine made with 2 L of water needs 597 g of salt.
% of the brine, not % of the water
Cheese brines are quoted as a share of the whole brine — salt ÷ (water + salt). That's why this page starts on “Total brine”. The same 23% brine is 29.9% if you measure salt against the water alone, so check which one your recipe means.
Storage brine
Cheeses like feta are kept in a much weaker brine. There's no official home figure; recipes vary, and one study stored feta in whey brines of 6.5%, 8% and 9.5% salt. Enter the strength your recipe gives.
More than salt
A good brine also matches the cheese's pH (a mismatch softens the rind or slows salting), sits at about 50–55 °F (10–13 °C), and is kept clean. Brine picks up whey, fat and microbes over time, so commercial makers filter or replace it.
Sources: University of Wisconsin–Madison Center for Dairy Research, “Keys to Managing Your Salt Brine” (D. Sommer); McMahon et al., “Influence of brine concentration and temperature on composition, microstructure, and yield of feta cheese”, J Dairy Sci 2009;92:4169–79. Informational only — not professional advice.