The short answer
With black tea, oxidation during processing shapes the style. After that, what matters most in your cup are the specific variety, the leaf amount, the water temperature, and the steeping time.
What happens during production
After harvesting, the leaves first wither. They're then processed and allowed to oxidize before being dried. The UK Tea & Infusions Association describes exactly these steps.
Withering simply means: the freshly picked leaves lose water and become soft. This step happens right at the start, before any processing begins.
Oxidation here means: compounds in the leaf react with oxygen from the air. Both color and flavor change as a result. With black tea, this process is deliberately allowed to run its course.
This has nothing to do with fermentation in wine. There, yeast converts sugar into alcohol. In tea, neither yeast nor alcohol is involved. Two very different processes sometimes share the same everyday word.
In China, incidentally, black tea is called red tea. The name refers to the color of the liquor, not the leaf. What's called black tea there is an entirely different category.
This doesn't matter for shopping here at home. But it does explain why imported packaging sometimes carries confusing labels.
Oxidation determines the style before you even hold the package in your hands. You can no longer change that part. Everything that comes after, though, is entirely up to you.
A workable starting point
Many black teas handle roughly 90 to 98°C (194 to 208°F) well. Three to four minutes of steeping is a reasonable starting point. The instructions on your specific packaging will be more precise, and they override any general guideline.
These figures sit close to boiling point. A kettle without a temperature setting is therefore usually fine for black tea. Steeping time is the lever you adjust here.
These figures are a starting point, not a rule. They give you solid ground from which to move in one direction or another.
Now comes the single most important thing to know about black tea. Steeping it longer doesn't make it stronger—it makes it more bitter.
The reason lies in the order things happen. Flavor compounds release from the leaf early on, while tannins follow later. Tannins are the compounds that make your mouth pucker and feel furry. So past the recommended time, what you're mainly adding is exactly what you didn't want.
If you want more strength, use more leaves for the same time. That's the whole trick. This is the most common mistake in tea-making, and also the easiest one to fix.
Stick to one change per attempt here too. Either more leaf or a different time, never both at once. Jot down briefly what you changed and how the tea tasted afterward.
After a few pots, you'll have found your own ideal settings for this particular tea. That applies to this specific package, not to black tea in general. With the next variety, the search starts over again—but much faster this time.
