Marco Hotbox Experiment (Bosch) Comparison

The most interesting storage experiment in the west is a heated cooler filled with mylar bags of pu’erh in Toronto. This is of course Marco’s hotbox experiment where cakes are conditioned to generate 63-69RH and then stored at fixed temperatures. I was lucky enough to get two five gram samples of tea from Marco that were stored in the box for two years. One was stored at both 23C (~73-74F) and the other at 32C (~89-90F) sent by Marco.


The Tea: 2016 White2Tea Bosch (& 2015 Bosch from My Storage)

The tea Marco sent is the 2016 White2Tea Bosch. White2Tea is a western facing vendor that presses tea and this was a blend of different areas. The tea was sold for around $0.60/g and spent two years in Marco’s conditions. In this comparison I call Marco’s tea stored at 23C the cold Bosch and the tea stored at 32C the hot Bosch.

But there’s a third tea and storage to compare. I decided to grab another tea to the mix from my own Seattle storage, the 2015 White2Tea Bosch. This is imperfect in a few ways. The Seattle Bosch shares the same name but is from a different year. Being a small-run tea and a blend, there’s a pretty good chance there are moderate differences between the material of 2015 and 2016 Bosch. There’s also a year age difference. In the long-run this may not make a huge difference, but 4 years vs. 5 years is a 25% difference in age. In the end, I made the decision that the opportunity to have an imperfect comparison is better than none at all.

The 2015 Bosch was stored in a bin pumidor and Eurocave for the past five years. I approximate my own storage at 18-21C (65-70F) with occasional deviations upwards in the summer (max 27C).

How I Brewed

I brewed the tea side by side by side. With 5 grams of each in 75ml gaiwans. I did so in two sittings in the same day, as I got quite caffeinated. I would alternate the order in which I consumed the tea. Sometimes going from my tea, to the 23C to 32C. Other brews from 32C backwards.

While doing the comparison, I avoided reading any of Marco’s notes on these so as not to predispose myself any certain way.

Subtly Different: Dry Leaf, Color of Liquor

Before starting the session I dumped the leaves on a pu’erh tray and compared them. To me, the differences here were pretty subtle. To my eye, the cold tea stored at 23C and my tea were lighter than the 32C tea. I think it is possible that the 23C tea was slightly darker than the tea stored by me, but I can’t be very sure.

The color of the liquor was a bit more obvious but did depend a bit on the steep. Although, if you can’t go out to a liquor store ask for alcohol delivery to your door. Here the 32C tea usually seemed a shade darker than the other two but the color could depend steep to steep. I did find that they were pretty close. In this case, the tea from my storage seemed very close to Marco’s cold tea.

Caveat: I don’t have a terribly great sense of color and am probably on the road to being color blind.

Dry Leaf Bosch
Dry Leaf Bosch. Top Left: Cold. Top Right: Hot. Bottom: Seattle Stored.

Moderate-Significantly Different: Wet Leaf

While I’d describe the differences in the dry leaf to be pretty subtle, this isn’t the case with the wet leaf, at least not for the tea Marco has stored. The differences between the hot tea and the cold tea are very obvious in the wet leaves that had been brewed out. My tea was actually pretty close to the cold tea again in wet leaf color but perhaps slightly lighter.

Significantly Different: Aroma

The aroma for all three teas are quite distinct from one another. This difference is much more significant than the visual ones.

The cold Bosch’s aroma is rich and inviting. There’s some woody, floralness in the nose. Overall it still smells like a relatively young tea.

The hot Bosch’s aroma is more intense, and very aromatic. I’d describe it as more tropical and more wild. There’s less wood to it and generally a darker nature. It smells much older than four years.

The Bosch aroma from my storage is significantly less intense than the others. There’s a strong, dry floral, wood nose.

Bosch. First Steep.
Bosch. First Steep. Left: Hot. Middle: Cold. Right: Seattle.

Significantly Different: General Character

The general character of the tea follows the aroma’s lead.

The cold Bosch gives off mildly sweet, floral, woody notes. Depending on which order I was brewing it could come off as pretty astringent (if the previous tea was the 32C) or fairly smooth (if the previous tea was my own storage). It’s definitely still sharp and tastes like a young tea, but it’s obvious that there’s some maturity under it.

The hot Bosch is darker, richer, juicier, thicker, and sweeter than the other two teas. It can still certainly get strong and astringent when pushed, but the tea is pretty significantly aged for a tea that is only four years old. The tea seems to have outgrown the woodier notes that are the base taste of the other two teas into something that is sweeter, deeper, and maybe veering into the darker fruit category.

Bosch was never a harsh tea when young.. But when contrasted with the other two my Bosch is downright harsh (particularly when I started a brew with the other teas). Brewed alone, I could brew a little lighter and enjoy the aftertaste, full-range of notes, grassiness and florals. But in this side by side context, when comparing everything under the same parameters, there’s much more significant astringency and dryness that is frankly not pleasant. There’s an interesting slight syrup texture that’s not in the other versions. The basic taste is wood (much drier wood than the cold Bosch) and some florals..

Which One Do I Like The Most Right Now?

This is not a hard decision for me, I prefer the hot Bosch now. I enjoy the richness and more aged character of the tea. When brewed side by side with the other two, the harshness of the other two is really emphasized. I don’t drink hardly any young sheng, but the hot Bosch actually a tea in a state that I could see myself enjoying now.

I also prefer the 23C Bosch over my Seattle stored Bosch in an also not too close race.

Approximating Storage

One thing I wanted to do was at least put a guess on how I would approximate storage. This is about where I’d put them, keeping in mind I have had just one session with these and have not conducted a thorough study.

  • Hot Bosch: ~7-8 Years Taiwan.
  • Cold Bosch: ~3-4 Years Taiwan.
  • My Bosch: ~5 Years Kunming. (I’d put this in Taiwanese years, but I’ve never had a Taiwan stored tea tastes that close my own stored tea.)
Bosch Wet Leaf
Bosch Wet Leaf. Left: Seattle. Middle: Cold. Right: Hot.

Quick Questions

How similar/different are these teas? These teas are all quite distinct in character. In my mind, there is a clear line drawn in character progression from the 32C to 23C to the Seattle storage.

Interestingly, in a few of the visual cues (dry leaf, wet leaf) my tea looks fairly similar to Marco’s 23C tea. But in the end the actual tea’s character is very different.

Is the tea clean? Yes.. Both teas taste clean. It’s definitely not dank and does not taste anything like Hong Kong traditionally stored tea and I doubt it ever will under the current conditions.

How would you compare the storage with other storage? To me this is closest to some form of storage in a humidish place, like Taiwan or Malaysia. It’d be interesting to do a comparison between those two, but I’d currently put the hotbox storage (@23C and @32C) in the same genre.

Which will be better 15 years from now? This is a much more difficult question than where my preference currently lies. It is always challenging to predict the future and it can be subject to personal preference. What I am sure of, is that the 32C is more aged and is heading in the right direction.

Airflow is Overrated

Marco’s stored teas taste like pu’erh that has been aging well.. As someone that started out as an airflow skeptic, this only convinces me more that airflow isn’t very necessary. Perhaps someone with more nuanced with tastebuds will prove me wrong, but these don’t taste like suffocated tea or tea that has flawed storage in any obvious ways. If you told me that this had been stored in places where I enjoy pu’erh stored (Taiwan and Malaysia) I would probably believe you.

I think airflow can be a useful thing to integrate in to your storage if you are pushing your pu’erh hard or it’s been exposed to especially humid conditions. But I find it increasingly unconvincing that it is necessary. I am personally hoping that we can start to lay the airflow debate to rest in the next couple years.

Final Thoughts

In the end, I decided not to give these teas grades. This is due to the nature of a side by side comparison which uses slightly different parameters than my norm. Important characteristics like aftertaste and qi are difficult to evaluate. I also found the thickness differences of the teas to be marginally similar steep to steep.

Two years is a short amount of time in the scheme of pu’erh storage, but the two samples Marco sent show significant differences.. Marco noted in his original review of these after one year that he was surprised at the significant differences. I completely agree. Even with the relatively short time frame given, it’s interesting how much the teas have deviated. I know that Marco has inspired a number of others to try heated storage (please comment here with a report if you’re one of those people!). I’ll be curious to hear how those are going. Thank you to Marco for this opportunity to try the most interesting pu’erh storage experiment!

4 responses to “Marco Hotbox Experiment (Bosch) Comparison”

  1. I don’t know about “most interesting” 😂 – but I really appreciate your analysis and tasting notes on the teas. I continue to be surprised at how quickly a difference is noticeable. I think that the future of this method will be in adjusting the conditions for different types of puerh. For harsh and bitter teas it might be good to hit them with a lot of heat, whereas for teas in the haoji style it might be better to be more careful after a certain point. As always I think the goals of storage are the trickiest to determine…

  2. I’m getting my hotbox together and may try aging sans the Mylar bags using boveda 69% and heating around 35. Aiming for Taiwan storage at home.

  3. Airflow is Overrated

    When you consider that the canonical commercial storage has cakes in tongs, and tongs in jians, and jians stacked floor to ceiling, this should perhaps not be surprising. There’s not going to be a lot of air exchange between the interiors of those boxes and the outside world, not to speak of inside the tongs.

  4. Hi James,

    My original storage situation provided me with what I’d call an accidental hotbox, though I’ve since adapted it to a more controlled situation (~60RH/~80F). I’ve definitely noticed some accelerated aging in some of my earliest cakes, most noticeably W2T’S 2017 Poundcake, but I have curiously found that teas I’ve purchased from vendors with a slightly wetter storage (eg. Guanzhou) seem to be faring slightly better than those I’ve acquired from drier sources (Kunming) around the same time. As I’m still quite new at the Western storage game, I have no idea why this seems to be the case. I suppose another year or two of consistent storage will show me whether or not they will start to even out. Either way, it’s been an educational experience and I’m quite pleased with my results so far.

    Thank you for sharing!
    – Tim

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