I have just read an interesting article regarding mold development on food. It seems that there is right now an argument going on about possible preservatives in a 14 year old McDonalds hamburger that looks as if bought the the same day.
In this German language article a TV sender has made a comparative test between 3 burgers - a McDonalds burger, a bio-burger without preservatives, and a supermarket burger - which could be quite interesting regarding Pu Erh storage.
Here's the link, for German readers:http://www.welt.de/vermischtes/article1 ... asser.html
and my quick translation of the for Pu Erh storage relevant passage:"The result was clear. The burgers that were kept for 60 days in fresh air had no visible mold. All 3 were just dried up as were the objects of demonstration by the artist and now also by the young Davis Whipple from Utah.
Under the microscope microbes could be found in the bio-burger and the one from McDonalds (in comparable density), though so few that they could not affect the exterior view of the dishes. Alone the product from the supermarket, with preservatives, was free of microbes.
In a second test run the dishes were packed airtight, and after a short time mold developed - equally in all 3 samples."
This is not really a proper scientific test, yet the results could be quite important for Pu Erh storage. I was told quite early on in my Pu Erh ventures that a certain amount of airflow and exposure to climate is very important for healthy aging of Pu Erh, and have done that in the past 10+ years i have home stored my Pu Erh (with very good results). I just keep my teas on shelves in a spot in my house which has a bit of airflow, yet is not exposed to direct fans, and which has no direct sunlight.
Given the result of the 2nd hamburger test run, it seems that airtight packing can increase mold development - at least in the burgers. But given that Pu Erh tea is, especially when young, not completely dry, and organic matter, this may also occur with Pu Erh.