Fermentation & Temperature

Thermometer

Measure the liquid, not the room — the brew runs warmer than the air around it.

Thermometer — original illustration

Original illustration — a generic example of this tool, not a specific product.

Specifications

Category
Fermentation & Temperature
Types
Digital probe, glass stick, dial, or adhesive strip thermometer
Range needed
40–120°F (4–50°C) covers brewing and cooling
Accuracy
±1°F (±0.5°C) is more than sufficient
Target band
68–82°F (20–28°C) for the first fermentation
Calibrate
Check in an ice bath; note the offset
Cleaning
Sanitise the probe between batches
Typical batch size
Any size

Thermometer

Measure the liquid, not the room — the brew runs warmer than the air around it.

Fermentation produces heat, so the liquid in an active jar is typically a degree or two warmer than the room. A thermometer that reads the actual brew, rather than the air on the shelf, tells you what the culture is actually experiencing. Digital probe, stick or adhesive strip thermometers all work; the important thing is that you check the liquid before you make a decision about the batch.

measurement temperature core
Best for
First Fermentation, Second Fermentation
Batch size
Any size

Applicable brewing stages

  • First Fermentation
  • Second Fermentation
  • Flavoring
  • Bottling
  • Cleaning & Testing

A highlighted stage means this tool has a direct role at that point in the process. Ticking several stages is normal — a thermometer, for example, is useful during both the first and second fermentation.

Safety notes

Do not use a mercury thermometer near food or drink. Glass thermometers can break against the rim of a jar, and broken glass in fermenting liquid is easy to miss. Sanitise any probe that goes into the brew, and never use the same thermometer for cooking raw meat and for brewing without a thorough clean in between.

Practical guidance

  • Take a reading from the middle of the liquid, not just below the surface.
  • Log the temperature at the same time each day so you can see drift before it becomes a problem.
  • A stick-on strip reads the glass wall, which is close enough for a trend but not for a decision.
  • Calibrate once and write the offset on the thermometer body in permanent marker.

Please read before you brew

This page is educational reference material, not professional brewing, food-safety or medical advice. Equipment handling, hygiene practice and local rules vary, and nothing here guarantees a particular brewing result.

  • Home brewing rules differ by country, state, province and municipality, and they change over time. Check your own local requirements — including any permit, licence, volume limit or minimum age — before you brew, bottle or share what you make.
  • Use food-grade equipment only. Vessels, bottles, tubing and utensils that were not made for food or drink may release unwanted compounds or shelter microbes.
  • Work in a well-ventilated space, keep hot liquids away from children and pets, and follow the manufacturer's instructions for every appliance you use.
  • Bottles under pressure can fail. Use bottles designed for carbonated drinks, do not over-prime, and refrigerate once the carbonation is right.
  • For anything involving gas pressure, electricity, high heat, chemical cleaners or acids, consult a qualified professional.

Finished kombucha contains trace alcohol and caffeine. It is not suitable for children, and anyone who is pregnant, breastfeeding, immunocompromised, diabetic or taking medication should speak to a healthcare professional before drinking it. Kombucha is a food, not a medicine, and it does not treat, cure or prevent any disease.

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