What you're stabilizing
Beverage and size route the methods and scale every dose. Beer takes a different path — chemical stabilizers aren't used in it.
Acidity and alcohol
Sulfite and sorbate both work harder at low pH and higher alcohol, so the right dose depends on these two numbers.
Sorbate + lactic bacteria makes a geranium-like off-smell. If malolactic might still happen, the tool won't recommend sorbate.
Chemical stabilization
If it restarts: pressure readout
sealed-vessel estimateEnter the fermentable sugar you're adding (or, for a soda, the sugar already in it). If every gram of it ferments out in a sealed bottle, this is roughly the carbonation and pressure you'd build — the difference between a fizzy surprise and broken glass.
Yeast alcohol tolerance
a soft signal, not a stopEvery way to make it stable
Chemical and physical, all the routes that apply to this beverage. Filtration and pasteurization are the only methods that are truly absolute; the chemicals are very effective inhibition, not sterilization.
How the numbers are worked out
Sulfite (the pH part). What protects a batch is the molecular SO₂, and only a fraction of your free SO₂ is in that form — the fraction collapses as pH rises. The tool uses free SO₂ = molecular × (1 + 10^(pH − 1.81)), targeting your chosen molecular level. That's why a pH 3.0 wine is safe near 13 ppm free SO₂ while a pH 3.8 wine needs around 80 — roughly six times as much. Above about pH 3.6 the free SO₂ required climbs toward the level you can taste and smell; the better fix there is to lower pH with a small acid addition before you lean on sulfite. The metabisulfite dose assumes potassium metabisulfite at 57.6% available SO₂, so grams = ppm-to-add × liters ÷ 576. Addition figures raise total SO₂ — how much ends up free depends on binding, so measure free SO₂ by titration if it matters.
Sorbate (the alcohol part). Potassium sorbate stops yeast from budding; it does not kill them and does nothing useful against an active ferment or a heavy yeast load. It also needs sulfite alongside it, because lactic bacteria metabolize sorbate into a geranium-like taint. It gets more effective as alcohol climbs, so the recommended sorbic-acid target falls from about 200 ppm under 11% to about 75 ppm above 14%. Potassium sorbate is 74.6% sorbic acid, and the dose is capped near the 250 ppm sorbic-acid sensory and legal ceiling.
Sodas and other low-alcohol drinks. Here the threat isn't a yeast you pitched but wild yeast and bacteria, and the soft-drink preservatives apply: sorbate plus sodium benzoate. Both only work in their acid form, so they fade as pH rises — benzoate is effective below about pH 4.5 (pKa 4.2) and useless near neutral. A low-pH soda or shrub can be held chemically; anything near neutral has to be made stable by heat or filtration instead.
The pressure readout. Fermenting sugar yields close to half its weight in CO₂ — the tool uses the species factor (sucrose ~0.51, dextrose ~0.45, fruit/honey ~0.49 g CO₂ per gram) — then converts to volumes at 1.96 g/L per volume and to equilibrium pressure with the standard carbonation relation at your storage temperature. A typical crown-capped glass bottle is comfortable to roughly 2.5–3 volumes and gets genuinely dangerous past about 4; champagne bottles and PET hold more. Treat the high end as glass-breaking, not a target.
Tolerance bands. Manufacturer alcohol ratings are a guide, never a hard wall. Yeast routinely creep past their numbers slowly over weeks, and a strain "at its limit" can still ferment a backsweetened bottle into a bomb given time and warmth. The band shown is a risk signal to weigh against the pressure readout above — not permission to skip stabilizing.
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