BubbleDrae said

oxidization levels of Oolongs

So, I’ve pretty much narrowed it down that oolongs are my favorite. I like how sweet they are of their own accord, and I like that you can brew them for multiple infusions. Mmm. Anyhow. I’m still trying to experience a good variety. So… can anyone pull apart some of the “descriptors” that accompany the label “oolong” for me?

Oxidization levels… light, medium, dark. This seems pretty straight forward, I suppose. Are certain levels named certain things? Like, I’ve noticed that “Pouchong” is always light. Any other names you can tell me?

How about some of these teas that are listed as “green oolongs?” Are these effectively lightly roasted oolongs?

Ti Guan Yin – this in my head is sort of a “subtype” of oolongs, but seems distinct to the others. Do these mostly tend to be low oxidization as well?

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Theoretically any tea can be made at any oxidation level. But traditionally Pouchong/baozhong is made at light oxidation level. Tie Guan Yin was made at higher oxidation level than modern day’s green style Tie Guan Yin, and lower oxidation level than Wuyi yan cha most of the times.

Also some oolong can be made with medium/high oxidation but light roasting. But low oxidation with heavy roasting is not commonly seen.

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I’ve had tieguanyins that are lighter and some that are darker. I guess it all depends on the producer. You can usually tell by the color of the leaves whether it will be light or dark. I don’t know if I said anything useful at all…

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TeaVivre said

Tie Guan Yin is a kind of Oolong tea, which sits between the full oxidized black teas and un-oxidized green teas. At present, Tie Guan Yin Oolong tea can divide into light oxidization and moderate oxidization.

The characteristics of light oxidization one: its brewed tea leaves is green, and many of the brewed tea leaves are broken. While the brewed tea color is also green, to some degree, it like the soup of mung bean, and the dry tea has a distinct orchid fragrance as well.

The main character of moderate oxidization Tie Guan Yin: it was made through a traditional way, so when compared it to light oxidization one, the latter has golden tea color, mellow taste, also the leaves are very complete after brewing.

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Hi BubbleDrae and others, an old thread but I thought the answers above were pretty inaccurate, so here’s a better (and long!) answer:

So firstly, oxidisation does very little to the colour of the leaves. Almost NOTHING. If anyone tells you that their tea is dark because of the long oxidisation, stop buying tea from them. Here’s two pictures I took myself – the first is a Wuyi Yan Cha after 18 hours of oxidisation (still very green) and the second is a Tie Guan Yin after about 12 hours of oxidisation (again, only slight discolouration on the edges of the leaves):


Try this experiment – pluck a healthy leaf from a nice evergreen tree, and put it in your house for 12-18 hours (at around 25 degrees celsius). Check the colour at the end – I very much doubt it will change colour at all.

Colour in oolong teas (the dark colour) comes from the post-oxidisation baking, drying and roasting. Oolong teas all experience different processing, but all will go through some phase of “sha qing” to stop oxidisation, which involves a short, extremely high heat (around 300 degrees). This still doesn’t necessarily change the colour much. Here’s a Tie Guan Yin leaf after the “sha qing” and a round of bruising unique to TGY processing:


Still green….

Most darker oolongs like Wuyi Yan Cha will go through multiple very light roastings and then drying phases, which is where the leaves turn from 95% green to perhaps 30% green. When a Yan Cha (or Dan Cong for example) is finished and ready to drink, it will still be fairly green – see this picture:


Sorry for the crappy picture – the leaves are quite brown, but still with strong green parts and definitely not the deep chocolate associated with most dark oolongs.

The dark, chocolate colour only comes from roasting. Red/black teas are completely dark because of their long and full roast, and Da Hong Pao (a Wuyi Oolong) is chocolate brown because of the roast. Generally the roast is lowish temperature, maybe 80-100 degrees for 1-2 hours.


If you’re a newbie I would recommend you to mostly ignore the oxidisation level as an indicator of taste, and focus on the roast level, if that oolong is roasted. Most of the time you won’t taste the relative oxidisation levels, but you will taste the roast levels. “Light”, “medium” and “dark” should normally refer the roast of the tea, which corresponds to the colour and taste very closely.

Normal Tie Guan Yin (Iron Buddha) is NOT roasted. Different TGY varieties are distinguished by the oxidisation period and farm location, but not by the roast level. Generally you have ‘pure’ TGY which has about 8 hours of oxidisation and a buttery taste, a ‘tuo suan’ which has a longer oxidisation and a sour and tingly taste, and then a variety in the middle. However, lots of farms also like to subsequently roast a TGY many weeks after it’s finished processing, but then it should be clearly labelled as “roasted TGY” or sometimes 浓香 nong xiang / 老铁 lao tie. You’ll see the difference in these two pictures between a medium-roasted TGY and a normal non-roasted TGY (these are the same teas, the only difference is the roasting):


I must confess I label my normal TGY as a “green oolong” but that’s mostly for marketing purposes – green teas sell better, and it’s a keyword that many of my customers are looking for, so I abuse it a bit :)

This was really informative. Thank you for taking the time to post this!

Wonderful information and pictures, thank you very much. :)

Will said

The bruising does cause a red edge or red spots on the leaf of teas with a traditional level of oxidation. It can be seen quite clearly, even on teas with a light roast (e.g., many dancong, very high oxidation teas like dongfang meiren, etc. From what I’ve heard, oxidation levels used to even be specified in red vs green (e.g., 7 parts green, three parts red). The reason a leaf that’s been picked doesn’t oxidize is because it hasn’t been bruised and withered the way oolong is before kill-green is done. There are some great pictures of the leaves (pp 67-68, 164) before the kill-green and before the first firing in Jason C. S. Chen’s “A Tea Lover’s Travel Diary”, which covers the production process of Fenghuang dancong and Anxi tieguanyin in great detail. Sorry, but this claim is nonsense.

Oxidation and roast will also color the tea broth differently, with more oxidation giving the brewed tea a more amber color, and more roast giving a more brownish color. So both contribute to the color of the brewed tea; either a very strong roast or very heavy oxidation can change the color dramatically (look at dongfang meiren, (Oriental Beauty), for example, which has little or no roast, but high oxidation).

The trend for a while was for everything to be super green, but does seem like there’s increasing interest in more oxidized and roasted oolongs in the past few years.

With some (most) modern Anxi tieguanyin, the red edge is torn or beaten off these days. Proper traditional TGY should have heavier oxidation in the base tea and not have the edge beaten off, and will have at least some roasting, though the roast will not always be super heavy. These days, though, many sellers of high fire tea (who buy the tea and do additional roasting, such as a lot of sellers in HK / SE Asia, etc) can only get the more modern style base tea to roast. For me, a modern TGY with a heavy roast almost always tastes too “green”, without the fruity flavors that a more oxidized tea base will give.

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@Will – the proper bruising of any TGY happens after the long oxidisation has been stopped by the ‘sha qing’ (very high heat quick fire). Same for other oolongs – any unintentional ‘bruising’ that happens during the rolling and shaping of the leaves happens after oxidisation has stopped. There’s a small amount of discolouration in leaves sometimes, but I’d say 95-99% of the finished red/brown colour comes from the baking and roasting.

Here’s a picture of a handful of highly oxidised 60-70% (脱酸, tuo suan) TGY from Gan De (感德) last year about midway through the bruising/shaping process (about 2 hours after oxidisation has stopped):


No visible brown other than the stems. This is a closeup of a single leaf from the same stage of processing:


Now you can see two places – on the right hand side and on the bottom edge – where there’s a tiny bit of red.

Finally, here’s the same tea I brewed while I write this :)


This is a finished tea and no red/brown on the leaf.

When you see lots of red/brown in teas occuring during oxidisation, it’s probably because the leaves have been treated poorly before oxidisation (ie. machine harvested, accidentally broken, crushed in transit). The oxidisation process for TGY is basically just placing intact, freshly picked leaves on trays in @23 degree Celsius rooms for 6-18 hours. It shouldn’t change the colour.

Regarding tearing edges off – whatever tearing of leaves happens can only be accidental/incidental and isn’t done to specifically remove brown edges. A farm processing maybe millions of leaves over a 10-12 day harvesting period simply doesn’t have the man-power or time to carefully tear edges off individual leaves. I’ve only seen that level of care given to competition grade teas, in which case, if they’re having to tear brown edges off, they’ve already lost :)

Regarding roasting – I guess it depends what you mean by roasting. TGY is heat treated in three places: sha qing (to stop oxidisating, high heat), during the shaping and bruising (it’s rolled multiple times for a 30-60 seconds in about 180 degrees C and then bruised again) and then finally it goes through a very light drying at the end (this turns the leaves completely dry and brittle). “Roasting” or “baking” for TGY specifically refers to putting the completely finished TGY in an oven again specifically to give it another different flavour, but then it’s not pure TGY any more.

Will said

The step I’m talking about is when the tea is tossed (whether in a basket or in a large tumbler) before kill-green. This is intentional, and is part of what makes an oolong an oolong. The presence of a red edge is entirely intentional, and does not indicate mass production or poor handling of the tea.

What do you mean “not pure TGY any more”? Tieguanyin is a varietal, not just a style of processing. Traditionally, TGY was charcoal roasted, like most oolongs, even when not heavily roasted in the Chaozhou style. These days, electric roasters or ovens are a bit more common, but using the style of charcoal roaster used for Wuyi teas is most traditional. The practices you describe do accurately describe the current style of production, but do not accurately describe the traditional style of production (and the claim that the leaves pictured above are 60-70% oxidized is insane; also, in the final tea, the edge has been beaten off intentionally).

I will try to scan some of the pictures from the book I mentioned to give a better visual reference.

In the meantime, here are a couple pictures from Stéphane’s blog; it’s a pretty good / representative example of a baijiguan leaf that shows the red edge. Like most baijiguan, it’s not heavily fired.

And a shot of dancong from Tea Habitat (click for higher res version):

Will said

Also, from The Leaf issue 7 (p9):

Traditional half-oxidized tea is savored for its aftertaste. But what is the difference between the two? Traditional half-oxidized “ripe yun type” is characterized by: three parts red to seven parts green; dark base, green midsection, and red along the edges; robust knots, heaviness; visibly red spots; and white frost on the surface of the leaves. “Delicately fragrant” Anxi Tieguanyin is characterized by: one part red to nine parts green; emerald green color and luster; pure, fresh flavor; light green at the bottom of the leaves; and few red edges or spots.

The biggest difference between traditional and “lightly fermented” [read: oxidized] tea is that the first is half-oxidized and stressing the “shaking” technique, placing importance on warm baking over a slow fire; whereas the second uses light oxidation low temperature air conditioning, and emphasizes delicate fragrance.

This article also discusses the ‘sour’ style TGY; it says (p11):

According to experts, this kind of “sour” in lightly-oxidize Tieguanyin comes about after drying by not promptly performing sha_qing (“kill-green” to stop the oxidation), thus drawing out a sour flavor.

So, yes, there’s more of a delay before the kill-green step, but not more oxidation than the tea would already have had.

Will said

This page also describes the process somewhat:


I believe zao qing is referring to ‘zuo qing’ in Pinyin (http://www.baike.com/wiki/%E5%81%9A%E9%9D%92)

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@Will – my point is that a Da Hong Pao and a TGY undergo extremely similar oxidisation periods, but one of them is chocolate brown and the other is bright green. When does the massive colour change happen? Not during the formal oxidisation stage.

When the DHP and TGY leaves come out of the oxidisation stage, they look pretty much identical (ie. the vast majority of the leaf is green). Yes, there’s some discolouration to differing degrees, and yes, Wuyi teas often start to have a red edge because they’re rolled around and tumbled more, but the huge colour change appears in the later stages of processing. I’ve been to Anxi and Wuyi every May/October for the last 3-4 years and I’ve seen these all directly myself, not books or internet. Maybe we’ve had different experiences at different farms or different regions…

The other point was to try help the original poster, because terms used to describe oolongs are often vague. Light/medium/dark could point to colour, oxidisation or roast level. Tea retailers should do better – if someone is saying that their oolong tea is chocolate coloured because of the long oxidisation period, it’s nonsense.

The TGY I posted a picture of was a batch I literally watched being processed last May. The leaves didn’t have any red edge before oxidisation, or before bruising, or after bruising, and it wasn’t roasted. There was no red edge to rip off in the first place. The tea gets ripped and beaten up during the bruising/shaping, but you can see there’s still green edges left to the leaf – there’s just no physical way the tea master has enough control during the bruising/shaping to tear the brown bits off and leave the green bits.

By “pure TGY” I mean 正味 (zheng wei) which is what’s used as the standard TGY here in FZ. The finished leaves are 95-100% green.

Someone else might have to weigh in here, but I’m fairly sure that the name “TGY” does indicates the processing method?

Will said

Yes, but the style of TGY produced most commonly these days is around 8-10% oxidized, which is why the red edge is so visible. You are correct that this is the Most common type produced since the early 90s, but it is not the only type.

My understanding is that the edge is generally intentionally taken off. If you look at many older or more traditionally processed TGYs, not only do they have a red edge, but the edge of the leaf isn’t torn up.

It’s true that it is difficult to find TGY produced this way in Mainland China now, but they do exist. Best Tea House of HK sells some more oxidized Anxi TGY, with a moderate roast, for example. I know a guy who runs a shop in Shenzhen who has done his own productions as well:
http://www.sanzui.com/bbs/home.php?mod=space&uid=13758&do=album&picid=66958 has one picture

Everything I’ve ever heard indicates that Tieguanyin is a specific cultivar, one which has a couple of subtypes (hongxin, as in red heart, and qingxin,a s in great heart). That’s one reason why Muzha Tieguanyin is also considered Tieguanyin, though it generally uses more traditional methods.

I’m not totally sure about his reasoning, or how far back this step goes, but this is a good photo of the beaten off edge, as well as one explanation of why:


新工艺中,红镶边大多已经去除 (In the new style of processing, the red edge is generally removed).

If you look at the edge of other oolongs, whether wiry shaped ones or rolled ones (high mountain oolongs, dong ding, Muzha tieguanyin, etc.), the edge is almost always much more intact.

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Brett said

This is a great discussion, thanks guys! I have always believed that TGY was a reference to the varietal of the tea plant, but often find that distinguishing between “pure TGY” and something other than such is a subjective debate. I have friends in Fujian and I have heard differing accounts, which leads me to believe that the answer lies somewhere ambiguously between science and tradition…

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