Does Dark tea age?
Dark tea is the category where ageing is not just possible, it is the point. Raw pu-erh, ripe pu-erh, Liubao, and fu brick are all made with the expectation that they will sit for years before being drunk. A young raw pu-erh can be aggressively bitter, and a decade of storage is what turns it into something most people want to drink.
This does not mean every dark tea improves indefinitely. It means dark tea is the only category where time is an ingredient rather than a threat. That is not a guarantee. It is a precondition.
It also means dark tea is the hardest category to age well at home. The conditions that produce good transformation are close to the conditions that produce mould, and the margin between them is narrower than most guides admit.
If you live somewhere with a dry climate, which includes most of Europe and most of North America outside the Gulf Coast, your default indoor humidity is probably too low for dark tea to change much. That is not a disaster, but it does mean a cake you keep in a flat will move far more slowly than the same cake kept in Guangdong or Hong Kong.
If it ages: store for the long run
Two different things happen depending on the tea. Raw pu-erh starts as essentially a sun-dried green tea, and over years its polyphenols oxidize and its microbial community shifts, dropping astringency and building the thick, sweet liquor that aged raw pu-erh is known for.
Ripe pu-erh has already been through a fast fermentation. What ageing does for it is mostly subtractive: the wet-pile smell from production fades, and the liquor gets cleaner and rounder. Liubao and fu brick sit somewhere in between, and both continue to change for a long time.
The variable that decides everything is humidity. Between roughly 60 and 70 percent relative humidity, the microbes and enzymes responsible for the change stay active without mould taking over. Below about 50 percent, transformation nearly stops, and a cake can sit for a decade and barely move.
A cheap hygrometer in the storage space is worth more than any amount of advice about ideal conditions. They cost very little, and they turn a guess into a number you can act on. If it reads below 50 percent for months on end, either add a source of moisture or accept that your tea is in storage rather than in progress.
If it does not: drink it
Above about 75 percent relative humidity, you are in mould territory, and the risk is not just a ruined cake. Deliberately wet storage, the practice known as shicang, does speed up the change, but it flattens the tea and carries a real chance of contamination. Most people are better off with clean, dry storage and more patience.
Some dark tea is not worth ageing regardless of conditions. Tea made from poor raw material, or from material that was already exhausted, will not develop complexity with time. It will just get darker and duller. Storage cannot add anything that was not in the leaf.
The same applies to tea that has been stored badly before you bought it. A cake that spent five years in a damp warehouse is not a five-year-old cake in any meaningful sense. It is a damaged cake that is five years old.
In practice this is the single biggest risk in buying aged dark tea. The market is full of cakes that have been deliberately stored hot and wet to imitate the look of age, a shortcut that produces the dark liquor and soft mouthfeel quickly while leaving the tea flat and sometimes unsafe. If a young-looking tea is sold as old at a low price, this is usually why.
A simple smell test
Before you commit to ageing anything, press the cake gently with your thumb. It should feel firm and dry and smell clean, with no sour or cellar-like note. A cake that smells damp or feels spongy is already in trouble.
Be sceptical of age claims in general. Cakes sold as twenty years old are common and genuinely well-stored cakes of that age are not. Without a credible provenance, a stated age is decoration. Buy the tea you have tasted, not the year on the wrapper.
Store cakes in paper, in a box or a breathable cabinet, somewhere that does not smell of anything else. Do not seal them in plastic, and do not keep them next to spices, coffee, or paint. Dark tea will take on whatever it is stored beside, and it will keep it for years.