There is often talk on the forum  about the hydration of doughs, and the advantages and disadvantages of higher or lower hydration.
Hydration refers to the proportion of water in a dough relative to the amount of flour. It is usually expressed in terms of percentage of total flour weight. To calculate hydration add up the weight of all of the liquids in the dough (including water in the starter), and divide by the total weight of flour in the recipe (including that in the starter). Multiply by 100 to get a percentage.
My standard loaves are about 70% hydration. More than that starts to get pretty tricky to handle. Bill swears by doughs at about 64%.
Although it is a question that I suspect many will already know the answer to, I thought that it would be interesting to make my basic recipe with different proportions of water.
To determine the effect on oven spring, loaf crumb and texture of varying hydration in a standard white sourdough recipe.
As in previous weeks I used the Pane Francese recipe  using my starter at 100% hydration. I made 4 half recipes (ie using 250g flour).
In loaf #1 I used 150g water
(Total water = 150 + 45 (in starter) = 195g
Total Flour = 250 + 45 (in starter) = 295g
Hydration = 195/295 x 100= 66%)
Loaf #2 = 160g water = 69%
Loaf #3 = 170g water = 73%
Loaf #4 = 180g water = 76%
(NB I did the recipe from memory, and forgot the small proportion of wholemeal flour - so the loaves this week were purely white)
This week I refreshed my starter twice at 12 hour intervals. On Friday morning I mixed the dough (three quick kneads at 10 minute intervals), then put it in the fridge. Friday evening I took the doughs out of the fridge and let them prove for about 4 hours at room temperature. They were probably a little underdone at this stage (relatively few bubbles on slashing), but I was going to bed, so shaped them, wrapped them in towels, and left them on the balconey outside my bedroom overnight (9 hours).
Baked the next morning. Single slash down the centre to minimise differences between the loaves.
Results (click on thumbnails for larger pictures)
The four loaves (left to right #1 to #4)
Loaf #2 (69% hydration)
Loaf #3 (73% hydration)
Loaf #4 (76% hydration)
There were some clear effects of dough hydration on loaf structure and crumb.
The lower hydration loaves opened up much more with slashing. (I attempted to minimise differences in slashing depth by setting my Stanley knife to make a 0.5cm deep cut. Bill has recently demonstrated the differences that slashing can make ). They had more obvious and more vertical spring. The two higher hydration loaves were flatter in profile.
There was also a more open crumb to the loaves the higher the proportion of water in the dough.
Interestingly the loaves this week had the best blistering of their crust that I have generated to date (see loaf 3 above). This was most evident in loaves 3 and 4. (I didn’t spray the loaves. They were loaded onto the stone, and a glass of cold water was chucked onto a hot oven tray below them just before closing the door.)
So what hydration should you use? Carol Field quotes an Italian baker who boldy stated ‘the wetter the dough the better the bread’ (I am paraphrasing). There are advantages and disadvantages of increasing the proportion of water in a dough. The dough becomes harder to handle and the shape of the resulting loaf is often harder to control, however the crumb does seem to be more open. I haven’t looked at a wide range of hydrations here - the range that I have covered are already at the ‘moist’ end of the spectrum. It would be interesting to look at doughs with 50%, 60% or 80% hydration. Another day perhaps…