As per the title, really.
What role does higher hydration play in the creation of bread, sourdoughs or otherwise?
A higher hydration loaf will give you more rise, more air bubbles, and a much more open crumb. In addition to those three things, it's much easier on your mixer and/or hands.
Many people use a stretch and fold technique instead of kneading the dough as well.
with the proviso, up to a point. You can still get a good open crumb with doughs of lesser hydration (say in the 65% - 70% range) if the dough is handled well during the folds and when shaping.
For commercial bakers, one benefit of a higher hydration loaf is cost: the more water, the lower the per unit cost of materials to make the loaf of bread.
Water is the basis of being able to make bread in the first place. Changing the percentage of this life giving fluid has an effect on the dough and before that on the preferment or starter. From a science standpoint, more water means the biology can move around more freely and will generally be more active and efficient at consuming the food source (flour/sugars). The dough will be softer and more pliable which makes it easier to rise under the power of the co2 gas that is produced, to a point. The down side is that the proofed dough will not stand up as well when it is softer from high hydration. The up side is that if other things like gluten development and remaining sugars are right, the dough may still rise acceptably and not bake like a Frisbee.
Generally speaking, the more you become adept at baking with higher hydration dough mixes, the easier it is and the lighter the bread will be. It took me quite a while to become proficient at handling 80% hydration dough. Once you learn the trick to it, it's very doable and there is no better feeling than handling a large boule of well developed soft dough.
I suggest you begin by adding 5% water to a recipe you are comfortable with and see for yourself how it handles differently. Try to keep the primary side (Top) of the dough constant as you gently fold and shape the dough. It is possible to never have your hands in sticky dough if you handle the floured side only and fold into the sticky side. There are many good videos that show this subtle method. Once you have mastered the new hydration level, add another 5% and start over.
Sorry if I went on here. Your question was about why higher hydration but I tried to help you understand how to bake with it. Once you understand the How, the Why becomes obvious.
I always thought that what we were looking for was the % of liquids in the final loaf, after it is baked. I assumed that this was the reason why the dutch ovens were so popular.
If we end up with 52% does it make any difference if we start with 80% or 70%?
I'm confused by all the techniques on kneading and stretch/folding. Can you link a video or two?
THere's a tab at the top of the page called "Videos." Check out the Back Home Bakery videos.
No, that's a very comprehensive answer, I thank you very much.
Now I understand this subject a little better, I shall indeed increase the hydration and experiment a little with it.
When I first started learning to bake and found The Fresh Loaf, I wanted to try Ciabatta. I liked the open crumb and heard the taste was great. I struggled with handling the dough so much, I stopped making it for a while. Every time I came back to it I got a little better. The videos are a great help. There is nothing like seeing some one else manage slack dough and make it look easy.