The four rules
Four rules: cool, dry, dark, and away from smells. Dark tea is the one category that breaks two of them on purpose, which is why it confuses people who have learned the rules on green tea.
Dark tea does not want to be especially cool, and it does not want to be especially dry. It wants stable room temperature, around 20 to 30 degrees, and moderate humidity, around 60 to 70 percent.
What it wants absolutely is darkness and isolation from odour. On the second point there is no compromise at all. A cake will absorb the smell of the room it sits in and keep it for years.
So the working version for dark tea is: stable, moderately humid, dark, and smelling of nothing. Paper wrapper, cardboard box, closed cabinet, and years of being left alone.
Why each rule exists
Temperature matters because the agents of change here are enzymes and microbes, and both slow sharply in the cold. A cake kept at 15 degrees will barely move in a decade.
Humidity matters more than anything else, in both directions. Below about 50 percent, transformation nearly stops. Above about 75 percent, you are in mould territory, and the risk is not just a spoiled cake.
Dark matters, though a wrapped cake is already protected. Loose dark tea, such as a ripe pu-erh broken out of a cake, needs the same darkness as anything else.
Odour matters because compressed tea is a long-term sponge. Cooking smells, paint, fuel, spices, and cleaning products will all end up in the cup, and there is no way to wash a cake.
Apply it to Dark tea
Applied to dark tea, the container is the paper wrapper it came in, inside a box, inside a cabinet. Do not use sealed plastic, vacuum bags, or an airtight tin.
All three stop the microbial and enzymatic activity the tea is meant to undergo, and in a damp room the first two also trap water against the leaf. This is the mistake that comes from applying good green tea instincts to the wrong category.
Store cakes together rather than separately. A box of cakes holds a more stable microclimate than a single cake on a shelf, and it costs nothing to group them.
Put a hygrometer in the cabinet. For dark tea this is not optional, because the gap between a cake that develops and one that moulds is about ten percentage points of humidity.
Make it a habit
The habit that matters is checking twice a year and otherwise doing nothing. Press the cake with your thumb, smell it, and close the box.
Firm and dry is right, and clean and earthy is the right smell. Spongy means water has got in. Sour means it has been there long enough to do damage.
Keep a simple list of what you own and when you bought it. With cakes that will not be drunk for a decade, memory is not a system.
And be sceptical of age claims when you buy. Cakes sold as twenty years old are common, and genuinely well-stored ones are not. Without provenance, a stated age is decoration.
If your home sits below 50 percent humidity for most of the year, accept that this is storage rather than ageing. The cakes will keep perfectly and change very slowly, and that is a legitimate outcome.
The alternative is a humidified cabinet, which works but costs money and needs maintenance. For most people the honest choice is to accept the slower timeline and buy tea they already like.
Temperature, by contrast, is the variable people worry about and need not. Anywhere between 20 and 30 degrees that stays steady will do. The humidity number is the one worth checking.
One last habit: store cakes away from anything with a smell, and check that space twice a year. Paint, fuel, spices, and cleaning products have all ruined more dark tea than humidity ever has.
Get those two things right and the rest of the rules can be broken. Dark tea is the one category where that is true.
The rules exist to protect tea. For dark tea, the goal is the opposite, and that is worth saying out loud.