Sourdough recipes are written in baker’s percentages, and the first time you meet one it looks as if the maths has gone wrong. The flour is 100 percent, the water is 75 percent, the salt is 2 percent, and the whole thing adds up to well over a hundred. That is on purpose.
Everything is a percentage of the flour
In baker’s maths the flour weight is always 100, and every other ingredient is expressed against it. So 75 percent hydration means 75 grams of water for every 100 grams of flour. It makes recipes easy to scale, because you change the flour and everything else follows.
Hydration changes the loaf
Lower hydration, around 65 percent, gives a tighter crumb and a dough that is easy to shape. Push past 75 and the crumb opens up, but the dough gets slack and sticky and much harder to handle. Most bakers settle somewhere in between once they know what their flour will take.
Do not forget the starter
The starter is flour and water too. A 100 percent hydration starter is equal weights of each, and if the recipe ignores it the real numbers drift. Add 200 grams of that starter to 1000 grams of flour and 750 grams of water and the true hydration is 850 over 1100, about 77 percent. Enough to change how the dough behaves.
Write down what worked
The loaf you are proudest of is the one you will want to repeat, and by the next bake you will not remember the exact hydration, the proof time or how warm the kitchen was. Keep notes and a photo of every bake and the good ones stop being accidents.
BreadMath is an app for Android and iPhone that does the baker’s percentages for you, keeps your starter on a feeding schedule and holds a photo record of every loaf, with no account to make.