Why your sourdough starter is not rising

1. The kitchen is too cold. By a distance the commonest cause, and the reason January starters stall.
2. It is between days four and eight. A lull here is normal and not a fault.
3. It rose and fell while you were not watching. A fast starter in a warm room can peak in three hours.
4. The feed ratio is too low. Not discarding enough starves the culture relative to its own mass.
5. The flour changed. Bleached flour and some low-protein flours slow a starter noticeably.
6. The water is chlorinated. A minor factor, and the last one to investigate.

1. The kitchen is too cold

A starter at 18C behaves like a much weaker starter at 23C. It is not broken; it is slow. In winter this single factor explains most stalls, and it is the reason recipes written by someone in a warm kitchen produce timings that do not match your jar.

The fix, for nothing: put the jar in the oven with only the light on and the door shut, on top of the fridge, or in a cupboard near a radiator. Do not buy a proofing box — see what beginners waste money on.

2. It is simply the quiet week

New starters usually bubble for two or three days, then go quiet for several more, then come back properly. The early activity is often not the organisms that will run the mature starter. If your starter is between four and eight days old and doing nothing, that is the expected behavior.

The fix: keep feeding on schedule and wait. Do not buy a replacement culture at this point; you will very likely reach the same conclusion a week later.

3. It rose and fell before you looked

A mature starter in a warm room can double in three hours and be back down by hour eight. If you feed it in the morning and check at bedtime, you may be looking at a starter that already did the thing you are waiting for.

The fix: mark the level at feeding time with a rubber band and check at intervals. If you see it above the mark at any point, it is working.

4. The feed ratio is too low

Adding a spoonful of flour to a jar that is already three-quarters full of starter is not a feed. The culture needs enough fresh flour relative to its own mass to make a visible difference.

The fix: discard down to about 50g and feed 50g of flour and 50g of water. If it is still sluggish, discard down to 25g and feed 50g of each — a bigger ratio, which strengthens a weak starter.

5. The flour changed

Starters respond to flour. Moving from whole grain to bleached white flour slows most starters, sometimes dramatically. If your starter was working and then stopped, ask whether you opened a new bag.

The fix: feed with unbleached flour, and add a spoonful of whole wheat or rye to a couple of feeds to strengthen it.

6. The water

Heavily chlorinated tap water can slow a culture. This is the last thing to investigate, not the first, because it is a smaller effect than any of the five above.

The fix: leave a jug of tap water out overnight, or use filtered water.

If none of this works

Start again with whole grain flour in a warm spot, or get a spoonful from someone with a working starter. A restart costs a cup of flour, which is less than the frustration of nursing a jar you have lost confidence in.