Pre-Infusion Versus Blooming

No, they're not the same. Wikipedia's page on pour-over coffee says so in a footnote: blooming is sometimes incorrectly also called preinfusion.¹ People mix them up because both wet the coffee before the main brew.

Two different brewing methods

Bloom belongs to pour-over and other methods where you pour water by hand over the grounds. Pre-infusion belongs to espresso. Espresso is made by forcing very hot water under high pressure through finely ground, compacted coffee.²

That difference is the reason the words shouldn't be swapped. One belongs to pour-over. The other is a stage of a pressurized shot.

What pre-infusion means to a maker

La Marzocco's wording is a continuous flow of water at low pressure that saturates the puck.³ Then a higher, steady pump pressure takes over. So there are two parts: the gentle flow, and the hand-off to full pressure.

The same page describes pre-brew as something else again. Pre-brew wets the top of the puck with an interrupted on, off, on sequence before brewing.³ Even among espresso makers, the labels aren't always interchangeable.

That matters when you read a manual. A feature called "pre-brew" in one manual may be a pulse of water, not a long low-pressure flow. Check the description, not just the name.

What the espresso side adds

One more point from La Marzocco: pre-brew and pre-infusion both happen before visible extraction.³ On an espresso machine, nothing shows in the cup during that stage. That's a feature of how a shot is built, with the water kept inside the group head, and it's another reason the espresso term needs its own page.

If you're reading a pour-over recipe, the machine pages here won't map onto it. If you're reading an espresso manual, don't look for pour-over timings in it.

Why the confusion sticks

Both ideas wet the coffee before the main brew. That overlap is the likely reason the words get swapped. Wikipedia still calls the swap incorrect.¹

Keep each word with its own method. Pre-infusion goes with espresso machines. Bloom goes with pour-over. Your reading gets easier.

What the bloom is

Bloom is the pour-over word. This site is about espresso machines, so it doesn't go into how a bloom works. Use a pour-over source for that.

A quick way to tell them apart

Ask two things.

• Is a pump or lever pushing water through the coffee? Then the word you want is pre-infusion.
• Is the water poured by hand? Then the word is bloom.

If a recipe tells you to "pre-infuse" a pour-over, it's using the espresso word for the bloom. Wikipedia calls that use incorrect.¹

Back to the basics on what pre-infusion is, or see how pump machines make the soft start.