Levain & preferment
How much ripe starter, flour and water to take to get the target preferment weight at the chosen refresh ratio. The ratio is starter : flour : water.
—ripe starter
—flour
—water
How it works
A 1:2:2 ratio means: for 1 part starter, 2 parts flour and 2 parts water, 5 parts total. The target weight is divided by the sum of parts, and each component is taken proportionally. The hydration of such a preferment is flour-to-water; with equal flour/water it is 100%.
Before building the preferment it helps to set aside 15–20 g of ripe starter in a fridge jar — a backup in case of failure. The smaller the starter share (1:5:5), the longer the ripening.