Bread crust baking up too hard usually comes from not enough steam in the oven, or from an oven temperature set higher than it should be; a loaf that has already baked can have its crust softened noticeably by brushing on a little water and warming it in a low oven for a few minutes.
Why does the crust bake up so hard?
Bread crust forms as moisture on the dough's surface evaporates and the starches and proteins there firm up; without enough moisture in the oven, that hardening happens much faster and in a thicker layer. That is exactly why bakery ovens blast steam in the first few minutes — home ovens usually fall short on that steam.
An oven set too hot has a similar effect, since high heat lets the crust harden too fast before the inside has fully baked. Dough kneaded with too much flour, on the dry side, can also bake up with a thicker, harder crust.
How do you soften a crust that has already baked hard?
A hard-crusted loaf can be brushed with a little water by hand or with a pastry brush, then warmed in a low oven at around one hundred fifty degrees for five to ten minutes — the steam released noticeably softens the crust. Sealing the bread in a bag lets its own moisture soften the crust somewhat, though that can also strip away the crust's crispness entirely.
For sliced bread, the simplest fix is wrapping the slices in a damp paper towel and warming them in the microwave for a few seconds; this softens the inside while easing up on the crust's hardness too.
What can you do before baking?
Pouring hot water into a separate tray at the bottom of the oven alongside the bread, or spraying the oven walls with water a few times, is a simple way to mimic a bakery oven's steam at home. Keeping the oven temperature within the recipe's range, and kneading the dough to a balanced consistency — neither too dry nor too wet — also keeps the crust thickness in check.
Not opening the oven door during the first fifteen minutes of baking keeps the steam inside from escaping early — steam lost too soon lets the crust start hardening earlier and thicker.
Does the type of flour affect crust hardness?
Dough made with high-protein bread flour builds a stronger gluten network, which can add to how firm both the crumb and the crust turn out; dough with whole wheat flour mixed in tends to bake up with a somewhat crispier but thinner crust, since the bran fragments partly break up that gluten network. Dough enriched with a little oil or milk generally bakes to a softer crust than a plain water-and-flour loaf.
Slicing bread the moment it comes out of the oven traps steam that has not had a chance to escape yet; letting the loaf cool on a wire rack for at least half an hour, ideally a full hour, helps the crumb settle and keeps the crust from losing moisture too fast and turning harder than intended.