I've been working with the 'Artisan bread in five minutes a day' master recipe, tweaking and adjusting and I've gotten just about everything the way I like it: thin, crackly crust, lovely open cell crumb, and slight tang in flavor. The only problem is that I get little to no oven spring.

Here are my modifications:

Hunk of dough held back from last batch (dissolved in some of the warm water)

3/4 tablespoon yeast

1 1/2 tablespoons coarse (kosher) salt

3 cups lukewarm water

2-3 cups white flour

seven days ago - I baked my usual two loaves of NKB which turned out to have a sour taste. I commenced a new batch - everything the same and after the suaul 20 hours of doing what it does - the dough has a sour smell - I used a new bag of flouor same brand - everything else is the wame. Anyone has any idea please - I miss my lovely smelling bread

Gerry