Hi Mark, a number of factors can play into the type of spreading you describe, so it's difficult for me to say exactly what's going on with your bread, but inadequate tension in the loaf could certainly contribute to spreading. If this is the case, you may find this blog post on shaping a boule helpful.

Other factors that might be playing into the results you're seeing: a very wet (high-hydration) dough, inadequate dough development, over-fermentation/over-proofing of the dough, and possibly a starter that could use a little more reving up before adding it to your recipe. 

Although it sounds like your starter is quite peppy when you add it to your recipe, it can be helpful to give your starter a few feedings at room temperature prior to adding it to an entirely naturally leavened bread recipe. These "revival" feedings after refrigeration increase the populations of wild yeast and friendly bacteria that are available to do the work of rising and flavoring your bread. During the feedings leading up to baking your bread you can encourage vigorous yeast activity by timing your feedings to line up with when your starter is ripe and at its peak. Allowing the starter to fall significantly between feedings can lead to sluggish yeast behavior. Since your starter is rising so rapidly, this could involve several feedings per day, so you might want to slow down the ripening process by reducing the percentage of starter you're feeding. By offering your starter a relatively larger meal that it will take longer to consume and ferment, you can slow things down so that a twice a day feeding routine will be enough to keep your starter vigorous. For example, instead of feeding with a 1:1:1 ratio (starter:water:flour, by weight), you could try something like 1:4:4: 50g starter + 200g water + 200g flour. I'm not sure if the activity level of your starter is contributing to your difficulties, but it won't hurt to give this routine a try for a few days and see if this changes your results. 

Temperature is also contributing to how rapidly your starter is rising, so if your oven with the light on is warmer than 80 degrees, you might consider allowing your starter to dwell somewhere slightly cooler. I would aim for somewhere in the low to mid-seventies. I know it sounds counter-intuitive to try to slow down the progress of your starter's ripening, and ultimately it may not be necessary, but in the long run I do think your starter may benefit from a bit more room temperature fermenation time. 

High-hydration doughs are challenging in many ways:  they can be harder to develop strenght in, are harder to shape, and are more likely to over-ferment. If you're working with a recipe that has over 70% water (the weight of the water as compared to the weight of the flour), then you might want to try a recipe that is a bit stiffer as you develop your sourdough baking skills. When working with wet doughs it can abe helpful to allow the shaped rise to occur in a proofing basket or a bowl lined with a very well-floured cloth, and to bake the dough in an appropriately sized Dutch oven, that will encourage the dough to rise up during baking, rather than spreading out. 

It's important to develop adequate dough strength so that your dough can retain it's shape and rise properly. There are lots of ways to develop dough strength, depending on the type of dough you're working with, so it's hard to give you a one size fits all answer to how to do this, but if you feel your dough is very slack when you go to shape it, this might be something to work on. 

Dough that has been allowed to rise and ferment for too long or at too warm a temperture is more likely to over-ferment, and over-fermented dough not only won't rise well, but will also suffer from deteriorating dough structure. If your dough feels very wet and rips easily when you shape it, then you may be working with over-fermented dough. Wholegrain flours tend to ferment more quickly than white flour, so if you're working with a lot of wholegrains, shortening your overall fermentation time may be helpful. You may also find this blog post on Desired Dough Temperature helpful in terms of controlling the pace of fermentation. 

I hope I haven't overwhelmed you with all this information! If you'd like to troubleshoot a little more precisely I would encourage you to call our Baker's Hotline at 855-371-2253. We're here M-F from 9am-9pm EST, and Saturday and Sunday from 9am-5pm EST. 

Barb

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