Why Oolong tea goes wrong
Oolong ranges from around 15 percent oxidation to around 70, a wider span than any other category. Two oolongs can need opposite treatment and both be correct.
The light end behaves close to green tea and the dark roasted end close to black tea, and everything in between exists on the shelf.
Most bad oolong comes from applying one rule to the whole range, usually whichever rule suited the previous tin.
The two mistakes below account for most of it, and both are easy to spot once you know what to look for.
The fix is not a better technique. It is a habit of checking two things before you brew.
Roast level is the other axis, and it matters as much as oxidation. A charcoal roasted oolong and an unroasted one from the same cultivar are close to different drinks.
Mistake 1: water too cool to ever open the rolled leaf
Rolled oolong is compressed into tight pellets or balls. Water below 90 degrees will not open them, and the centre of the pellet never brews at all.
What you get is a thin, watery cup with a faint aroma, and the natural conclusion is that the tea is poor. It usually is not.
Use a full boil. Oolong is the category where the hottest water you have is nearly always right, including for the light green styles.
Give it time to open. The first steep of a ball rolled oolong is often weak for exactly this reason, and discarding it is normal practice.
Look at the leaf after two steeps. If the pellets are still partly closed, the water was too cool or the steeps too short.
The one exception is a very lightly oxidised, unroasted oolong, where 90 degrees is kinder. Everything else wants 100.
Higher altitude makes a difference too. High mountain oolongs from above 1000 metres are denser, and they hold up to boiling water better than a low elevation leaf does.
A quick check is to drop a pellet into hot water and watch. If it has not begun to unfurl after 30 seconds, the water was not hot enough.
Mistake 2: too little leaf for the volume
Oolong is brewed at a far higher ratio than Western habit suggests. Seven grams in 100 millilitres is standard, roughly 1 gram of leaf per 14 millilitres of water.
A level teaspoon in a mug is about 2 grams. In 300 millilitres that is 1 to 150, close to a tenth of what the tea needs.
Under-dosing cannot be fixed with time. Steeping a small dose for longer gives a thin, hollow cup rather than a stronger one.
Weigh it once. After a week you will know what 7 grams looks like in your own pot, and the scale can go back in the drawer.
Then use short steeps. Twenty seconds for the first, adding five each round, and a good rolled oolong will run eight to ten.
If you prefer a Western pot, use 5 grams in 300 millilitres for three minutes. That is the compromise, and it gives you one cup instead of ten.
If 7 grams feels excessive, check your vessel. The ratio is what matters, and 7 grams in 100 millilitres is the same concentration as 3.5 grams in 50.
Water matters less here than with delicate teas, but a heavy mineral content still mutes the aroma. Filtered water is worth using for the light styles.
The habit that prevents both
Check the roast before you set anything. A pale green pellet and a dark twisted leaf from the same category want different water, different ware and different expectations.
Use boiling water by default. For oolong it is right more often than it is wrong.
Weigh the leaf. This is the single change that most improves oolong for most people.
Smell the wet leaf after the first steep. That is where the character lives, and at that point it tells you more than the liquor does.
That is the habit: boiling water, a weighed dose, short repeated steeps. The tea does the rest.
Taste the first steep and the fifth side by side when you get the chance. The change between them is what you are paying for with a good oolong.