Does anyone have any thoughts on whether the diameter of the jar used for storage affects the ability or rate of doubling/expansion? For instance, if my jar is 4 inches wide but my starter after feeding is only 1 inch deep, is it more difficult for the starter to gather strength to push upward?
The volume increase will be less the smaller the diameter of the jar. Exactly how much less is difficult to assess, and will be a nonlinear function of diameter.
The optimal shape for fermentation is a sphere....probably because it minimizes heat loss. The more you deviate from this shape, the longer it takes to increase in volume. Your starter would do better in something with a smaller diameter.
It has a volume of 1 U.S. cup. In addition to being a good size for the small quantity of starter I keep on hand, it has straight sides. That makes it very easy to see how much the starter has risen after a feed. The jar's height is maybe 1.5x the diameter.
There have been times when it was kept in a wider, shorter jar of the same volume but I don't recall any notable difference in expansion rate.
Paul
I like a more narrow and taller jar, simply because it is easier to estimate the rise.
Mine is fed twice daily and is kept out of the refrigerator. My starter is kept small, 45 grams in total. It is stored in a straight sided, 6 oz juice glass. I keep a few of these glasses on hand.
Dan