Strength

Many of these recipes specify strong flour. This means wheat flour with a relatively high percentage of the proteins that combine to form gluten. The characteristic lower height and large, uneven crumb structure cells in certain continental-style breads are achieved in part by using flours with lower and/or weaker protein, which is less elastic and so stretches out, and in places the walls between cells (the holes or bubbles) will break down to form larger ones.

If you want to move your baking up a gear, it’s worth trying to find millers or flour suppliers willing to give you advice on the appropriate flour to use to achieve particular results, or suitable for the characteristics of the type of bread you are trying to make.