My tea smells musty or damp

In short

Almost always moisture. The important distinction is between a stored dark tea developing an expected earthy character and any tea that has actually taken on damp — the first is normal and the second is not worth drinking.

Likely causes, in order

Most likely first. Answer the question under each one before moving on — several of these look alike in the cup and are told apart only by what was done to the leaf.

1. 1. The tea absorbed moisture

   Storage

   Check: Was it stored somewhere humid, near a kettle, or in a container that was not fully dry when filled?

   Fix: Leaf that has taken on damp does not recover, and drying it out does not restore it. Discard it and store the replacement in an opaque airtight container away from steam.

2. 2. It is a dark tea developing normally

   Storage

   Check: Is it a sheng or shou pu-erh, Liu Bao or aged white tea, and does the smell read as earthy and sweet rather than sour or mildewy?

   Fix: Aged dark tea legitimately smells of damp wood, forest floor and old books. That is the character it is stored for. Sour, sharp or genuinely mildewy is a different thing and indicates storage that went wrong.

3. 3. Sealed while still holding moisture

   Storage

   Check: Was a dark tea meant for ageing kept sealed in plastic rather than in a ventilated space?

   Fix: Tea intended to age wants airflow. Sealing it traps moisture and produces mustiness rather than maturity, which is the opposite of what the storage was for.

Tea types this applies to

• Dark tea and pu-erh

When this cannot be fixed

Tea that has genuinely taken on damp cannot be restored. Airing or re-drying it removes neither the smell nor the cause, and the result is not worth the cupboard space.

Guides covering this

• Reading processing faults in the cup — A surprising amount of what a drinker experiences as not liking a tea is a specific, nameable manufacturing error. Learning to hear the difference between a fault and a style is the fastest way to stop blaming yourself for a disappointing cup.
• What actually degrades tea, and which vector matters for which tea — Six things act on stored leaf — oxygen, moisture, heat, light, odour and time — and they do not act equally on every category. Knowing which one dominates for the tea in front of you is more useful than any general rule.
• Telling stale tea from a tea you simply do not like — Both produce a cup you do not want to finish, and the two have nothing in common. One is a tea that has lost something; the other is a tea that has something you did not want. Three quick checks separate them reliably.
• The water in stored tea, and why it is the variable underneath every rule — Almost every storage instruction anyone gives is really an instruction about how much water the leaf is holding. Understanding tea as a material that trades moisture with the air around it makes the rules derivable instead of memorable.
• Storing tea in a humid climate, where the general advice inverts — Almost all English-language storage writing assumes a temperate house that is too dry. In a subtropical or monsoon climate the problem runs the other way, the ageing categories become easy and the fragile ones become difficult, and several standard recommendations stop working.
• Re-drying a tired tea: what heat can put back and what it cannot — Gentle heat removes water and some absorbed odour, and there is no domestic process that returns an aromatic compound that has left. Knowing which of the two problems a tea has decides whether an intervention is worth attempting at all.

Related problems

Sharing a cause category, a tea type or a brewing method with this one.

• My pu-erh tastes exactly the same as when I bought it — A cake bought several years ago to age has not noticeably changed, and it was stored carefully.
• My tea goes damp within weeks and I live somewhere humid — Leaf that arrived loose and crisp becomes soft, slightly clumped and quiet within a few weeks, and the aroma flattens long before any best-before date is close.
• My matcha powder has gone dull green or khaki — The powder that was vivid green when the tin was opened is now olive, khaki or faintly brown, and the bowl looks muddy rather than bright.
• My refrigerated tea has gone damp and lost its aroma — Tea kept cold has become soft or slightly clumped, smells muted, and tastes flat and papery within weeks of being put away to protect it.
• My tea tastes of the cupboard it was kept in — The dry leaf carries a note that does not belong to it — spice, coffee, cleaning products, or simply a generalised kitchen smell — and the same note comes through in the cup.

Sources