Blog 39: The Bubbles You See? It’s Called Tea Foam

Updated: Oct 19, 2018

Ever since starting this tea blog, we’ve been getting great questions on a daily basis. Recently, a reader who lives in New England emailed us with a series of questions that caught our attention: What are those bubbles when you infuse a tea? Are bubbles bad or does it mean it has pesticide? What do you do with the bubbles? This reader also kindly shared answers that she found from various sources. Unfortunately, most answers are wrong or incomplete. Today, let’s talk about these “bubbles”.


Tea Foam

First, there is a name for “bubbles”. It’s called “tea foam” (Chinese: 茶沫, pronounce: Chá Mò). Tea foam often emerges and floats on the surface when you first infuse a tea. In ancient China, tea foam was considered as a treasure. In Jin Dynasty (Chinese: 晋代, AD 265-420), Mr. Du Yu (Chinese: 杜育) wrote an elaborated description of tea foam (although it refers to matcha in that era and is different to do with modern tea) in his work Chuǎn Fù (Chinese: 《荈赋》): “惟兹初成,沫沈华浮。焕如积雪,晔若春敷”. It roughly translates into: after the infusion, when matcha powder are sinking into the bottom of the cup, a layer of white “treasure” appears, and it shines like snow and glosses like blooming flowers in the spring.


The appearance of tea foam is actually the result of a chemical reaction involving a natural substance found tea leaves: tea saponin. Tea saponin is an organic substance produced by tea plants. Of course, tea plants don’t release tea saponin to make “tea foam” for us. The purpose of tea saponin is to protect tea plants. Not only tea saponin serves as antibiosis for tea plants, but also it’s poisonous to some insects. Tea saponin creates an invisible armor that protects tea plants.


All tea plants generate and release tea saponin, but not all tea leaves make the same amount of tea foam. The amount of tea foam of a tea differs based on its tea-making process and how we infuse it. For example, when infusing Wu-Yi oolong (Yancha), we see more and thicker tea foam than that of a typical green tea. That’s because in Wu-Yi oolong tea-making, there is a process called “the rolling” (Chinese: 揉捻, pronounce: Rou Nian). One of the purposes of the rolling process is to release tea leaves’ inner substances. Tea saponin is one of the substances that is released to the surface of tea leaves. A good rolling releases more tea saponin to the surface of leaves; thus, it’d be easier to generate tea foam. The integrity of tea leaves also affects tea foam. Broken leaves have a larger contact surface with water, so it creates more tea foam at a faster pace. Finally, how we infuse water plays a crucial role as well. If we pour water faster, tea saponin would react faster and create more tea foam. If we use a “high infusion” (see previous blog), we’d get more tea foam as well.


The Rolling Process in Wu-Yi Oolong (Yancha)

Since the appearance of tea foam is natural, tea foam is not something you should worry about. And it is definitely not the result of pesticide as some online posts speculate. Tea foam is also not a criteria to judge whether a tea is good or not. We should NOT judge a tea based on how much tea foam a tea generates.


So, what do we do with tea foam? Commonly in Wu-Yi oolong, after the first infusion, we use the lid to skim tea foam off the surface. This practice does not make tea taste better. Actually, this “skimming” is an advanced skill because if done wrong or too slowly, tea is often over-steeped and can taste bitter and dry. The purpose of “skimming tea foam” is to have a better and clearer view of your tea leaves and tea soup. If you’re new to tea or a casual tea drinker, you don’t have to do it.


I hope you enjoyed today’s blog. As always, if you have any questions or suggestions, please leave a comment, tweet us @valleybrooktea or email the author directly at zhang@valleybrooktea.com. Please also follow us on Instagram @valleybrooktea and join our mail list to get our daily tea updates and our latest promotions! Finally, we have a semi-annual SALE on black tea products! Use code: semiannual and save 20% on all black tea products!


We’d like to thank our reader Kristen for her wonderful questions. This blog is also inspired by Chen and her researches and articles. If you’re interested in reading more of her works (all in Chinese), please email zhang@valleybrooktea.com for more details.