Modified Hotbox Design for Puer Storage

This post will detail my personal heated storage system.

My heated storage system is a modified version of this design. As I ran into various issues throughout my time experimenting with it, I had to make some adjustments. These adjustments were: installing a second heat mat on the ceiling of the hotbox (affixed using Gorilla tape), placing the temperature sensor inside a mylar bag (detail below) for a more accurate temperature reading/control, and using bookends to position the cakes and keep them in place.

I tried installing a fan to improve the evenness of heat distribution, and it was an improvement to the single heat mat design, but using two heat mats (which meant no space for a fan) worked much better in practice, with an average temperature differential of -0.5 degrees Celsius from the sensor’s reading.

Parts List

My System

The black line is drawn over the temperature sensor, which is oriented horizontally at roughly center of mass:

Try to replicate the environment of your cakes for your temperature sensor. Since the cakes are in mylar bags standing up, your sensor should be as well. Place the sensor inside a mylar bag and tape it (oriented horizontally) from inside. Place this mylar with the sensor in it in the center of the hotbox, with even amounts of tea on each side. The location of the sensor should be at center-of-mass.

This mylar bag holds the temperature sensor, and should be placed in the center of the box:

Keep the hotbox mostly full to improve temperature stability. Note that there’s also such thing as too full. This is a reasonable amount of tea to fit in the box:

Best Practices

  • Pre-condition the tea at room temperature by throwing a Boveda pack and a cake of tea into a sealed mylar bag. Every couple of weeks, check the generated relative humidity by removing the Boveda pack and placing a calibrated hygrometer into the bag with the tea and sealing the bag for 12 hours. When the tea has reached your target humidity, make sure to remove the Boveda before placing the sealed bag into the hotbox. (Note: the time it takes to measure generated RH depends on the compression of the tea among other factors. Most loosely compressed tea cakes will get you an accurate reading in only 2 hours, but it’s better to wait extra just to be sure.)
  • Use bookends to position the mylar bags and keep them in place.
  • Upon removing a cake of tea from the hotbox, open the mylar immediately to prevent condensation inside the bag. You can close the bag once the tea has cooled down.
  • Wait a month after removing your tea from the hotbox for any serious evaluation. Puer can (in some cases) suffer jet-lag after major temperature swings.


  1. So from reading Mgualts experiment…he advised conditiong the cakes, then storing sealed with no humidity pack…is this the practice you follow? I’ve read some people seem to think leaving the packs in mylar with the cake any longer than it takes to condition the RH of the cake is inviting mold problems.


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