The formula
classic: salt = water × % · equilibrium: salt = (water + meat) × %
Where it comes from
There are two ways of brining and they do not give the same result. The classic one works the salt out on the water and works by time: salt keeps moving into the meat for as long as it is in there, so going over on hours ruins the piece. The equilibrium one works the salt out on the total weight — water plus meat — at the percentage you want the meat to end up at, and there the salt stops moving once the two sides even out. That is the whole difference: with equilibrium brining, forgetting the piece in there for another day does not spoil it.
How to work it out by hand
- Pick the percentage: 5 % for a classic brine, 2 or 3 % for equilibrium
- Pick the base: water only for classic, water plus meat for equilibrium
- Multiply the base by the percentage
- For a classic brine, work out the time from the thickness of the piece
What is worth knowing
The timing rule for a classic brine is roughly one hour per centimetre of thickness at five per cent, and proportionally less if the brine is stronger. An equilibrium brine needs the opposite: at least twelve hours per centimetre for the salt to spread, and after that it makes no difference. As for the percentage, 2 % leaves meat seasoned without tasting salty, 3 % is where a home-cured ham sits, and above 6 % you are into preserving rather than cooking. Sugar is not just flavour: it holds moisture and helps browning.