First, the reassuring bit

Almost every sourdough starter that goes quiet, sulky or downright smelly can be rescued. A starter is just flour and water colonised by wild yeasts and friendly bacteria, and it responds to very ordinary things: how much you feed it, what you feed it with, the water you use, and how warm it is. If yours has stalled, the answer is usually one small adjustment rather than a fresh start. Here is how to work out which one.

What "normal" actually looks like in the first fortnight

New starters rarely behave like the tidy timetables online suggest. A typical pattern in a UK kitchen goes something like this:

• Days 1–2: a stiff paste that smells of wet flour. Little happens.
• Days 2–4: a sudden burst of bubbles and a rise, followed by a collapse. This is the false rise, driven by bacteria that thrive before the yeasts get going. It is not your starter "working" yet.
• Days 4–10: often the grim stretch. It may smell of cheese, plasters or nail varnish and look flat. The yeasts are still establishing themselves.
• Week 2 onwards: reliable bubbling, a domed rise a few hours after feeding, and a pleasantly sour, yeasty smell.

Most starters are ready to bake with somewhere between 10 and 21 days. Rushing this stage is the single most common reason people give up.

It smells wrong – what the whiff is telling you

Smell is your quickest diagnostic tool.

• Nail varnish remover, pear drops or acetone: hunger. The yeasts have eaten everything and are producing alcohol. Feed it, and feed it more generously.
• Stale beer or ripe fruit: healthy and active. Bake with it, or feed and carry on.
• Cheesy, sickly or like plasters: usually too warm, or a bacterial phase that has overstayed. Move it somewhere cooler and keep feeding.
• Grey liquid on top: that is hooch, a sign of hunger rather than spoilage. Stir it back in for extra sourness, or pour it off for a milder loaf.
• Furry patches, or pink, orange or black streaks: mould. Throw it away and start again. Do not try to salvage it.

Feeding ratios: weigh, don't scoop

Volume measurements are the biggest hidden cause of a sluggish starter, because a cup of flour and a cup of water weigh wildly different amounts. Use a set of digital scales and feed by weight.

Equal parts is the standard starting point: 1 part starter, 1 part flour, 1 part water. So 30g starter, 30g flour, 30g water. Keep it small — you do not need a kilner jar the size of a biscuit tin, and a modest jam jar is plenty for a household loaf.

When things stall, change the ratio rather than the routine. In a warm kitchen, or when your starter is sluggish, move to 1:5:5 — 20g starter with 100g flour and 100g water. That gives the yeasts a fresh, unacidic buffet and often produces a dramatic recovery within 24 hours.

Flour matters too. Wholemeal and rye carry more nutrients and wild yeast than white, so a spoonful of either in an otherwise white feed acts as a booster. Organic stoneground flours tend to be livelier than heavily treated ones.

Water quality and temperature

UK tap water is treated with chlorine, and in many areas chloramine, both of which can slow a starter down. Two easy fixes:

• Draw a jug of water and leave it uncovered on the counter overnight so the chlorine dissipates.
• Use filtered water, or bottled still water if you live in a very hard water area.

Temperature of the water matters as much as its chemistry. Lukewarm is right — roughly 20–25C. Anything above about 40C will kill the yeasts, so never use hot tap water straight from the boiler.

Room temperature is the other half of the equation. The sweet spot is 24–26C. An airing cupboard is usually far too hot and will push your starter towards a cheesy, sludgy state. Better spots are the top of the fridge, a shelf beside the boiler, or a microwave with the door left ajar and a mug of warm water inside. A cool kitchen will not kill a starter, it will simply slow everything down — give it days rather than hours before judging.

Reviving a neglected jar

If your starter has been in the back of the fridge since autumn, it is almost certainly still alive. Bring it to room temperature, pour off any hooch, then feed it at 1:5:5 and repeat twice a day for two or three days. Stirring daily redistributes the yeasts and stops a skin forming on top.

For long-term storage in a small kitchen, feed once, let it sit for an hour, then refrigerate. It will keep for several weeks between feeds. A jar of dried starter flakes in the cupboard makes a useful backup if you ever need to start again.

The guiding principle is consistency. Same flour, same water, same time each day, and small adjustments one at a time. Most starters that seem hopeless are simply hungry, chilly or underfed — and all three are easily fixed.