Drawn to its outside size
For temperature control around a starter jar
Brod & Taylor Sourdough HomeA small heating-and-cooling chamber for a jar, rather than a full dough bowl.
41 to 122°F, heats and cools8 × 10 in outside
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Mold on sourdough starter: when to throw it out
Throw the starter out if you see fuzzy spots (white, green, blue or black) or pink or orange streaks or patches, or if it gives off a smell that is not the usual sour or alcohol smell. Do not try to scrape it off. A grey liquid or a dry skin is not mold and can be dealt with. A thin white film is harder to judge by eye; if you are not sure it is harmless, start again.
Throw out: fuzz of any colour, pink or orange streaks, a smell that is not the usual sour or alcohol smell. Fine: grey or dark liquid (hooch), a dried crust, a sour or alcohol smell. Unsure: a thin white film with no fuzz. It may be kahm yeast, a surface yeast, but you cannot be certain by eye; when in doubt, start again.
Mold or not?
A smell can mean spoiled too: King Arthur's sourdough FAQ says to throw out a starter whose smell is not the usual clean, sour one, an alcohol smell being fine. When in doubt, start again: a new starter takes a week or two, and a spoonful from a friend's is faster still. See how to make one.
| What you see | What it is | What to do |
|---|---|---|
| Raised fuzzy spots, any colour | Mold | Throw out, start again |
| Pink, orange or red streaks or patches | Bacterial contamination | Throw out, start again |
| Grey, brown or black liquid on top | Hooch | Pour off or stir in, feed |
| Hard, dry skin | Dried starter | Remove it, feed from the middle |
| Thin white film, flat or wrinkled | Possibly kahm yeast; you cannot be certain by eye | When in doubt, throw out and start again |
Preventing mold
Move the starter to a clean jar every week or two, wipe the rim after feeding, and keep the lid loose rather than off. Regular feeding keeps the starter acidic, which is what protects it. A clear jar makes problems easy to spot.
Keep a backup
A spoonful of dried starter in a jar is insurance against mold or an accident. See drying and freezing a starter.
Questions bakers ask
Can I scrape mold off my starter?
No. Mold threads can reach beyond what you see. Throw it out and start again.
What does pink in a starter mean?
Pink or orange colour is a sign of unwanted bacteria. Throw the starter out.
Equipment for this job
Keep what you own when it does the job. These are the other exact models we profile.
Drawn to its outside size
OXO Good Grips 11 lb Stainless Steel Food Scale
For seeing the display past a wide bowl
OXO Good Grips 11 lb Stainless Steel Food ScaleA pull-out display helps keep the reading visible under larger containers.
11 lb (5.0 kg), reads in 1 g steps