What Gases Are Released During Coffee Bloom - Coffee Bloom Function - How Much Water for Coffee Bloom

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The basic equipment needed for pour-over coffee includes: pour-over kettle, filter paper, dripper, thermometer, timer, electronic scale, and coffee grinder. Not only does the taste of the coffee beans themselves matter, but many factors such as water temperature, flow rate, direction, filter paper choice, grind size, and more will all affect the resulting flavor.

The Importance of Blooming

There is a very important but easily overlooked step in the brewing process, and that is blooming!

Generally, astringency mostly comes from the later stages of brewing, where extraction time is too long causing the astringent sensation. However, blooming can still be a source of astringency, and this type of astringency can be felt from the moment it enters your mouth until you swallow, making your flavor defects overwhelmingly obvious. It's difficult to cover up by adding water or reducing overall extraction time, which is truly frustrating.

Common Causes of Astringency in Blooming

So if blooming causes astringency, what does this indicate about your technique?

It can mainly be divided into 2 categories:

1. Uneven Water Distribution

This is more common among beginners, or it can happen if your pour-over kettle is difficult to control. When your coffee grounds absorb water unevenly, the degassing will also be uneven. Essentially, extraction within the coffee bed is happening by chance—some areas may be over-extracted while others are under-extracted, which naturally leads to the production of astringent flavors.

The problems caused by uneven water distribution are actually quite easy to fix. Practice your circular pouring motion using the spent grounds from previous brews—practice 20-30 times, and your water distribution will be much smoother next time.

If your pour-over kettle is too difficult to use, consider replacing it. A good kettle is worth the investment, as cup after cup of poorly brewed coffee is essentially wasting money.

2. Too Gentle Water Application / Using the "Spreading Water" Technique

When your water application is very gentle, or when you use the so-called "spreading water" technique—gently placing water on the surface of the coffee grounds to allow them to fully absorb water—there isn't actually much of a problem. This is an excellent technique. However, pay special attention: blooming for too long may cause astringency. The reason is that with gentle water application or spreading water, the water is placed on the surface of the grounds without enough force to push the water into the coffee bed. It can only rely on gravity and diffusion to slowly moisten the coffee grounds. Therefore, the contact time between water and coffee grounds will be longer than with more forceful water application. If you then use a long blooming time, it may lead to over-extraction and produce astringency.

Solutions for Blooming Astringency

The solutions are basically two:

A. Reduce blooming time to under 30 seconds.

Test several times to determine the limit of your blooming time, and don't exceed this time. Basically, this will prevent astringency.

B. Slightly increase the force of your water application.

Apply a bit more force when pouring water, or be more spontaneous with your water control, allowing your water to flow toward the bottom of the coffee bed along with the pour-over kettle. When the water has some additional force, it won't stay in the coffee bed for too long. Then you can explore the limits of blooming time to achieve a balance between water gentleness and blooming duration.

Furthermore, blooming time varies depending on different beans. For example, dark-roasted beans have more vigorous degassing, so blooming for about 25 seconds is usually sufficient. Light-roasted beans can handle blooming for 30 seconds without issues! Taking FrontStreet Coffee's Golden Mandheling as an example, blooming for about 25 seconds, you can observe the blooming surface change from moist to matte—at this moment, it indicates that blooming is complete.

FrontStreet Coffee: A roastery in Guangzhou with a small shop but diverse bean varieties, where you can find various famous and lesser-known beans. They also provide online store services. https://shop104210103.taobao.com