In my experience, there’s no reason to assume that it’s because of the dough type. Both can get good oven spring and ears. Due to the way the yeasts and bacteria in a sourdough work, I find sourdough breads to be more finicky than pure yeast ones.They can get softer and flatten during the final rest, where yeast-only breads typically keep the surface tension and shape better.
I recommend you take a closer look at
- Proofing time:
Aim for slightly under instead of fully or even slightly over. Note that the margin of error is smaller for yeast breads, especially if you use the “fast” recipes with a rather high amount of yeast.
- Shaping:
A good surface tension helps the slashes to open better.
- Slashing technique:
Flat, almost horizontal cuts with a swift blade gives the coveted ears, vertical cuts just open up like a blossom unfolding.
- Humidity during the initial phase:
Don’t just spritz a bit of water in the oven and forget the “place a bowl in the oven” recommendations, that won’t give you a sufficient humidity level in the oven. You need quite a bit of thermal mass (some place a tray full of stainless steel nuts and bolts in the oven) and enough water that you should get to evaporate in one go. I usually splash a scant cup of water just off the boil right into the oven when I have just placed the loaf. (Careful, that’s a lot of steam and you can hurt yourself if you aren’t quick. Some ovens even can warp due to thermal shock, but I can live with that.) Open the oven door for a minute when the first phase is done and your oven spring has happened, usually by the time you lower the heat. Or bake in a Dutch oven.