I have been told to "just push the hydration up" by strangers on the internet roughly once a month for seven years, usually under a photo of bread I sold out of by nine in the morning. So in March I ran the test properly, on one Saturday, with one sack of flour, and wrote every number down.
Hydration is total water over total flour, expressed as a percentage, and the word total is where most published recipes quietly lie to you, because the starter is flour and water too. . If your starter is at 100% hydration, half of its weight is flour and half is water, and both halves belong in the sum. A "75% hydration" recipe that ignores 200 g of starter is not 75% of anything.
Four doughs. Total flour fixed at 500 g each, so the only variable is water. Starter at 20% of total flour, held at 100% hydration, which means 100 g of starter carrying 50 g flour and 50 g water. Salt at 2% of total flour. Therefore:
Target Total Total Flour Water Starter Salt Dough
H flour water added added (100%) weight
65% 500 325 450 275 100 10 835 g
72% 500 360 450 310 100 10 870 g
80% 500 400 450 350 100 10 910 g
88% 500 440 450 390 100 10 950 g
Same flour throughout: sifted strong white wheat, one 25 kg sack, opened that morning. Same starter, taken at the same point of its cycle, four hours after a 1:5:5 feed at 28C, when it was climbing and not yet flat. Same bulk temperature, 26C measured in the dough. Same folds, at 30, 60 and 90 minutes. Same shaping, same 14 hour retard at 5C, all four loaves on the middle deck of the same Rofco B40 in the same bake, 250C with steam for 20 minutes, vents open at 230C for 22 more.
Autolyse 40 minutes, flour and water only, before the starter went in. Salt added at the first fold, not at the start, purely because that is how I always do it and I did not want to change my own habits mid-experiment. Bulk 4 hours 15 in a 26C box. Preshape, 25 minutes bench rest, final shape as boules, into linen-lined baskets, straight to 5C. Baked out of the fridge with no warm-up. I ran the whole thing a second time three weeks later with the loaves in swapped positions on the stone. Every measurement moved by less than 3 mm, so the deck is not the story.
Oven spring here means one thing only: height of the loaf at its tallest point on the stone the second before the door shut, against the height of the cooled loaf, both taken with a steel rule standing on the deck.
| H | Handling | Base width, mm | In, mm | Out, mm | Spring, mm | Crumb | Verdict |
|---|---|---|---|---|---|---|---|
| 65% | Stiff, almost dull to fold. Shapes in one pass. Holds a seam like it wants to | 148 | 62 | 96 | +34 | Fine, even, small round holes, tight near the base | Excellent sandwich bread. Slightly close for my taste |
| 72% | Slack for the first fold then it firms up. Shapes cleanly. Skin stays intact | 156 | 58 | 99 | +41 | Open, irregular, no wall thicker than about 2 mm, translucent | Best loaf on the table. Not close |
| 80% | Sticks to the bench, wants two shaping passes, skin tears at the seam | 178 | 51 | 84 | +33 | Big holes at the top third, dense wet band along the bottom | A worse loaf that photographs better |
| 88% | Pours. Cannot be shaped, only persuaded. Flattens in the basket within an hour | 203 | 44 | 69 | +25 | Large caverns, gummy walls, thick pale base | Failure. Edible, not saleable |
Note the confound before you point at it: the 88% dough weighed 115 g more than the 65% dough, because more water means more dough for the same flour. It went into the oven with more mass to push upward and a lower starting height, both of which should flatter it. It still sprang least. And it spread 55 mm wider at the base, which is where all that extra volume went: sideways.
72% won and it won by 7 mm over the next best, which is not a rounding error at this scale.
Two separate mistakes wearing one coat.
The first is that a hydration percentage is a number about your flour, not about your bread. Absorption varies by wheat, by protein quality, by extraction rate, by how the mill treats the grain, by what the harvest was like. The Öland flour I use for the Friday loaf says 15 g protein per 100 g on the bag and it is considerably weaker than the sack I ran this test on, which says less. Protein on a bag is not gluten strength. So when somebody says they bake at 85%, they have told you something true about their sack and nothing at all about yours. The number does not transfer, and it is passed around as though it does.
The second mistake is that we started scoring bread on a photograph. A big open irregular crumb with 4 mm walls and a hole you can see daylight through is a structural failure that happens to look like an achievement in a cross-section shot. It leaks butter. It falls apart under an egg. Its base is always denser than the top, because the gas went up and the water went down, and that pale wet band along the bottom of a very wet loaf is not "custardy crumb", it is water that never left.
I sell bread to people who eat it. Since March the shop dough has run at 73%, up one point from where it was, and that change came from measuring, not from an argument.
If you want an open crumb, the levers that actually moved it in my notes are fermentation time, dough temperature, and how much you damage the gluten during shaping. Water is the fourth lever and it is the one everybody reaches for first because it is the only one you can change by pouring.