
Heated Storage 2017-2024

Here we see the same tea, Dayi’s batch 502 of the 2005 8582 recipe, stored for 11 years in Taiwan, followed on the right with 8 years of room temp (21-23C) storage in a Mylar bag, and on the left by 8 years of 32C heated storage as I described here: Hotbox system. Read also about conditioning, about Puerh storage anxiety, and finally about the risks of humidified storage. In short, the tea is stored sealed in a mylar bag or stainless sealed container at 32C in an insulated box, without added humidity.
Early experiments with added humidity and higher temperatures (Boveda packs and/or 40C temperature) were unreliable, required maintenance or monitoring, and/or led to mold, so were terminated.


The original Hotbox system is still going strong after 8 years of almost uninterrupted service — I say almost because there are sometimes power failures, usually no more than one per year. Besides this, no maintenance has been required, except that I have had to re-humidify a few cakes due to poor seals on mylar bags (these were all on bags that I open frequently). As I have said several times already, better than Mylar are the Onyx stainless steel containers with latex seal; these are ideal for puerh storage, in my experience. Also, heat-sealing mylar works much better than ziploc seals.



The tea on the left is like a slightly louder, darker, thicker and more resinous version of the tea on the right, which is more towards dry fruit. This 8582 has had the benefit of a 11 year head start in Taiwan, but it seems to be aging well in gently heated storage in its own generated humidity.
Recommendations for Puerh storage
Based on my experience and on the horror stories I have seen from storage discussions online, I can make the following recommendations for storing puerh if you do not have access to a good natural storage environment.
For a newcomer to Puerh: Seal your samples and cakes in Mylar at room temperature to keep them safe from contaminants and to keep their humidity level stable. A common size for use with Puerh cakes is the 1 Gallon Ziplock seal with 5.0 Mil thickness — this will hold two cakes comfortably. An excellent alternative is the 23cm diameter Onyx stainless container. This is dead simple and requires no setup or maintenance. It will keep your tea in good condition, but expect it to age slowly.
For a bigger collector of Puerh: Start with the above, and place the mylar bags + stainless containers in an insulated container with a weak heat source and a thermostat, so that it maintains around 23C (see the Hotbox). If you believe your tea is too dry, you may condition it before going into heated storage, but I do not recommend putting humidity sources of any kind into heated storage. Ideally your mylars should be heat-sealed, but if you prefer ziplocs then I would monitor humidity as it can drop over the course of years, especially with used ziploc seals.
An alternative approach: The main alternative to Hotbox storage is the Pumidor. It requires more humidity maintenance and it does appear to be a significantly slower aging method as it happens at room temperature, which for most people is 20-24C (although iirc Oxford might consider 14C an appropriate room temperature), but it has two main advantages of its own: first, you get to experience your collection in a more immediate sensory way, which can be enjoyable, and second, it allows significantly more air exchange, which relates to the main question posed below.
Open questions
The main remaining question of hotbox storage, in my opinion, is whether the tea is aging “as it should”, meaning in a similar way to natural storage in a tropical climate. There is a good argument that microbial activity is crucial in proper puerh aging, not only for humid storage but also for dry/natural storage. If this is true (and I suspect it is) then is this microbial activity possible in a “sealed” container? So far the results are encouraging, but we don’t have a clear picture yet.