What a 20% Brine Actually Means
Almost every brining instruction you will read specifies a saturated or near-saturated brine, and most quote a figure somewhere near 20%. What that percentage actually refers to is worth pinning down, because two reasonable readings of it give different amounts of salt.
Percent of what?
Brine strength is conventionally expressed as salt as a share of the total brine mass — water plus salt — not as a share of the water alone.
So a 20% brine is not 20 g of salt per 100 g of water. It is 20 g of salt in 100 g of finished brine, which means 20 g of salt and 80 g of water. Solving that for the salt you add to a known volume of water:
salt = (C × water mass) ÷ (1 − C)
For 4 litres of water at 20%: 0.20 × 4,000 ÷ 0.80 = 1,000 g of salt. If you had read the percentage the other way you would have added 800 g and made a 16.7% brine, which is a meaningful difference in how the cheese salts.
Worked strengths
| Water | Target | Salt | Total brine | Salometer |
|---|---|---|---|---|
| 4 L | 15% | 705.88 g | 4,705.88 g | 56.8° |
| 4 L | 20% | 1,000.00 g | 5,000.00 g | 75.8° |
| 4 L | 23% | 1,194.81 g | 5,194.81 g | 87.1° |
| 10 L | 18% | 2,195.12 g | 12,195.12 g | 68.2° |
Note how the salt required accelerates as the target rises. Going from 15% to 20% adds about 294 g; going from 20% to 23% — a smaller step — adds another 195 g, because the divisor (1 − C) is shrinking. Near saturation, small increases in strength cost disproportionate amounts of salt.
The saturation ceiling
Salt does not dissolve indefinitely. At around room temperature, water saturates at roughly 26.4% salt by weight, and the brine calculator refuses targets at or above that because they are not physically achievable — the excess simply sits on the bottom of the tub.
That is also what the salometer scale is measuring. A brine hydrometer reads 0–100 degrees across 0–26.4% by weight, so 100° salometer is full saturation. A 20% brine reads 75.8°, which is why traditional recipes talk about a "75 degree brine" and mean the same thing.
Why not just saturate everything?
A fully saturated brine is not automatically better. Very strong brine draws moisture out of the cheese surface rapidly, which can produce a tough, over-salted rind while the interior is still under-salted — and on some styles it causes a slimy or slippery surface.
Most recipes sit somewhere in the high teens to low twenties for this reason. The right figure is the one the style calls for, and the calculator's job is making sure you actually hit it rather than approximating.
Things that change how much salt the cheese takes up
Brine strength is only one of four variables, and the others are easy to overlook:
- Time. The dominant one. Salt uptake continues for as long as the cheese is in the brine, and doubling the time matters more than a couple of percentage points of strength.
- Cheese size and shape. Salt moves in from the surface, so a large wheel needs far longer than a small one — and a flat disc salts faster than a tall cylinder of the same weight.
- Temperature. Cold brine works slower. Brining is usually done cool, which is both a rate decision and a safety one.
- Cheese moisture. A wetter curd takes up salt faster than a dry pressed one.
Which is why "brine for X hours per kilo" style guidance exists and why it is style-specific. Strength is the variable you can set exactly; the rest is the recipe's business.
Calcium, and the mistake of pure brine
A brine made from nothing but salt and water will leach calcium out of the cheese surface, softening and sliming it. Established brines avoid this because they have equilibrated with the cheeses that passed through them.
The usual fix for a fresh brine is a small addition of calcium chloride, and often a little acidification so the brine's pH is closer to the cheese's. Recipes vary on quantities; the principle is that the brine should not be dramatically different from the cheese it is about to sit against.
Reusing brine, and when not to
Brine is traditionally kept and reused, and it improves with use. It also accumulates whatever the cheeses brought with them.
Keep it cold, keep it covered, and skim anything that forms on the surface. Check the strength periodically — each cheese removes salt and adds water, so a working brine drifts weaker over time and needs topping up; a hydrometer or the calculator with a fresh weight measurement will tell you where it is.
Discard it if it turns ropy or slimy, develops an off smell, or if it has been sitting warm. A brine tub is a salty, cool, wet environment with organic matter in it, and while high salt is genuinely inhibitory, it is a hurdle rather than a guarantee — particularly at the lower strengths, and particularly if the brine has drifted weaker than you think. When in doubt, mixing a new one costs a bag of salt.