Quick Diagnosis
What are you seeing on the starter?
🛒 Recommended Products
We recommend the following tools for this recipe:
Glass Jar for Starter (KneadAce)
Wide, clear jar makes monitoring activity and cleaning easier
Jar Spatula (U-Taste)
Thin spatula removes starter down to glass for cleaning and feeding
Digital Kitchen Scale
Accurate feed ratios reduce contamination risk
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Causes & Solutions
True mold (fuzzy green/black/blue growth)
commonSymptoms:
- • Fuzzy or powdery spots with distinct green, black, blue or white tufts
- • Spots appear separately from normal bubbles
- • Unpleasant musty smell, not just sour or alcoholic
Why does this happen?
Mold is an aerobic fungus that grows on surfaces when the starter is exposed to contaminants, insufficient acidity, or sits undisturbed for long periods. Unlike typical starter microorganisms, molds form visible colonies on the surface.[1][2]
🚨 Immediate Fix:
Discard the starter. Mold spores can penetrate below the surface; removing the top layer is not safe. Clean container thoroughly with hot soapy water and sanitize. Start a fresh culture from a trusted source or your saved dried starter if uncontaminated.
📅 Long-term Fix:
Keep starter in a glass jar with tight lid between feeds, maintain regular feed schedule, and store in fridge for slower activity if you feed infrequently. Maintain acidity by regular refreshments so pH stays low enough to discourage mold.[1]
🧪 Test:
Visible fuzzy colonies with distinct coloration are definitive for mold; do not attempt to rescue by scraping.
Hooch (liquid from hungry starter)
very commonSymptoms:
- • Thin layer of brown/clear liquid on top
- • Starter is watery, separated, and smells strongly of alcohol
- • No fuzzy growth
Why does this happen?
Hooch is the liquid by-product of fermentation when a starter is hungry. It is not mold. It indicates the population of yeast/bacteria consumed available food and produced alcohol and acids.[1]
🚨 Immediate Fix:
Pour off or stir back in, then feed the starter with equal parts flour and water by weight using a digital kitchen scale. Repeat twice daily until activity returns.
📅 Long-term Fix:
Keep a regular feeding cadence. For room-temperature maintenance, feed once or twice daily; for fridge storage, feed weekly and discard any hooch before refreshments.
🧪 Test:
Hooch is liquid and spreads; no hairy or powdery surface. Smell is alcoholic rather than musty.
Pigmented bacteria (pink/orange/tan streaks)
commonSymptoms:
- • Pink, orange, or red coloration in the starter
- • Often appears streaky rather than fuzzy
- • Off smell that is unpleasant (not just sour)
Why does this happen?
Certain bacteria can produce pigments and indicate contamination. These organisms can be undesirable or even potentially harmful; colored streaks are not typical of a healthy starter and signify instability or contamination.[2]
🚨 Immediate Fix:
Discard the starter. Clean and sanitize the container and tools. Start new starter or refresh a reputable dried/stable culture.
📅 Long-term Fix:
Use a clean glass jar and jar spatula for feedings, avoid wooden utensils that can harbor microbes, and follow a reliable feeding schedule to maintain a stable acid environment that suppresses contaminants.[1][2]
🧪 Test:
Colored streaks or pigments are a sign to discard; do not attempt partial rescue.
White film / pellicle or wild yeast bloom
mediumSymptoms:
- • Thin white film across the surface (not fuzzy)
- • Smell may be mildly sour or alcoholic, not musty
- • No colored spots or fuzzy growth
Why does this happen?
A pellicle (thin film) can be a harmless protective layer produced by some yeasts or lactobacilli in low-oxygen conditions; it's different from mold. It often forms when starter is stored for a while without feeds.[2]
🚨 Immediate Fix:
Scoop out the starter beneath the film, discard the film, and feed. If unsure, the cautious approach is to discard, but many starters recover after regular feedings.
📅 Long-term Fix:
Avoid long gaps between feeds, and keep starter loosely covered to restrict excessive oxygen contact. Maintain regular refreshments to preserve a healthy microbial balance.
🧪 Test:
Pellicle is smooth and thin; mold is fuzzy and textured. If in doubt, discard for safety.
Poor hygiene or porous container
commonSymptoms:
- • Repeated contamination despite regular feedings
- • Mold recurs after cleaning
- • Use of wooden bowls, plastic with scratches, or unwashed tools
Why does this happen?
Porous surfaces and microscopic residues harbor spores and bacteria that re-seed starter. Inadequate cleaning or open containers increase contamination risk.[1][2]
🚨 Immediate Fix:
Switch to smooth, non-porous containers like a glass jar. Thoroughly clean and sterilize tools and environment. Replace any old cloth covers with breathable but clean lids.
📅 Long-term Fix:
Use a dedicated clean set of utensils (e.g., jar spatula), store starter in a high-side container to minimize splash contamination, and avoid touching starter with unclean hands.
🧪 Test:
If contamination repeats without any change in feeding, container or utensils are likely sources.
🆘 Can I save it?
I found hooch (liquid), not fuzzy mold
Solution: Pour off or stir in the hooch, then feed with equal-weight feeds (1:1:1 or stronger) using a [digital kitchen scale](https://amzn.to/4pUMVHi). Feed twice daily at room temperature until it doubles reliably.
Success chance: high
Thin white pellicle but no fuzzy growth
Solution: Remove the film, discard, feed, and watch for rising activity. If smell and activity normalize, continue regular maintenance.
Success chance: good
Colored streaks or fuzzy mold
Solution: Discard starter and all contaminated utensils/containers. Start fresh. If you have a dry backup that was never contaminated, revive that instead.
Success chance: low — discard recommended
Prevention
- ☐ Use a clean non-porous container (recommend a glass jar)
- ☐ Weigh feeds with a digital kitchen scale and maintain predictable ratios
- ☐ Keep a regular feeding schedule so acidity stays stable
- ☐ Avoid leaving starter uncovered in dusty areas—use a breathable but clean cover
- ☐ Replace wooden utensils with easy-to-sanitize tools like a jar spatula