Moldy Pu'erh!!!

[Rickpatbrown]

I opened up my pumidor tonight, and it smelled off. It had a mildew-like smell emanating from it. I checked a couple bricks and cakes and low and behold, there was a significant amount of mold in about half of my tea. Such a bummer.

The good news is that this is my shou pumidor and it's not my main focus. I have two wine coolers that I keep around %68-70 RH with saturated NaCl/sucrose solutions in a jar. Temperatures fluctuate between 60-70°F in the winter and 65‐80°F in the summer.

I'm not sure what went wrong. Obviously, artificially increasing humidity in a closed space is a recipe for mold. A fewthings jump to mind.
1) I rarely open the shou pumidor. Since I dont focus in shou, that door stays shut and perhaps air exchange is helpful to stave off mold.
2) My shou cabinet is much more sparsely packed. Maybe the two humidity jars were too much for such a all amount.
3) I used only saturated NaCl (no sucrose) for about a year and a half. RH would get to about %70-75. Started worrying about mold, so I added the sucrose to keep it around %68-70.
4) I program the thermostat in my house to drop to 60°F at night. I hate being warm. Maybe the 10° temperature swing causes some condensation?

The picture is the worst cake. It's on the sample of 2017 YS Crimsom rooster. I ha e an unpped cake of the same tea that dowsnt have any mold on it. There was some on a 7562 brick that was wrapped in paper and in its box. And there were some other YS samples that had mold.

I checked my sheng pumidor and dont see any sign, but obviously I super freaked out now. Any suggestions?

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[thea_philosophia]

The RH is too high. Those temperatures dip way to low, and sudden fluctuations are no good.

I try to keep mine at a solid 70F 65RH in the winter (anything less is, in my opinion, a high risk for mold). I've only just started tracking RH since I had a mold issue recently (same deal... shou pumidor that got ignored and left too close to the ground for too long), but I'm hoping I can get them to a steady 80F 70RH this summer.

Opening frequently is a must to move the air around and avoid pockets of humidity. Same with rearranging cakes. I put a weekly alert on my phone and I just open them all real quick and give a wave with the lid to move the air around bit and I try to rearrange cakes once ever month or 2.

[Jules_Ludwig]

I opened up my pumidor tonight,

Is your Pumidor a closed plastic box? If so, I highly recommend not using such a box for long term storing, especially if the cakes are also humidified in the box.
I would suggest a bamboo basket, or an unglazed clay jar, that some air can circulate.

[karma]

I opened up my pumidor tonight,

Is your Pumidor a closed plastic box? If so, I highly recommend not using such a box for long term storing, especially if the cakes are also humidified in the box.
I would suggest a bamboo basket, or an unglazed clay jar, that some air can circulate.

Strongly disagree. In western dry countries this kills tea.

[Rickpatbrown]

Yeah. The RH inside during the winter is %30-40. When I taste Kunming stores tea, I see how low humidity and temperature affects tea. I really dont care for Kunming stored tea.

If it's not possible to store tea in a pumidor, than my only option is to buy tea that has been aged in Malaysia, Taiwan, Guandong, etc. This will be very expensive. I dont even know where to find 30 year old tea for less than $500 a cake.

I've been struggling with the desire to stock up on high quality tea, but this is another reason to chill a bit. Luckily, I didnt loose $10,000 in tea ... but if I continue down this road blindly, that might be my fate in 15 years ...ugh.

I looked up the dew point. For RH 70% at 70°F, your looking at a 59.8° dewpount. Man, I'm really cutting it close.

I think I'll readjust my thermostat to stay above 65.

[vuanguyen]

Using this calculator, at a RH of 65%, there is no risk of mold at any temperature.

http://dpcalc.org/

[vuanguyen]

Correction to the above statement using the calculator. At 65% RH, the only temp where there is risk of mold is at 82F but it will take 1186 days for mold to form.

http://dpcalc.org/

[Rickpatbrown]

@vuanguyen
I'm not sure how they come up with that calculation. That's an interesting tool.

My thought about the dew point was that if the temp dips below it, air could get condensation on the surface of the tea. Then RH doesnt matter.

Idk it's all just guessing right now.

[Jules_Ludwig]

Strongly disagree. In western dry countries this kills tea.

I use Boveda packs in my clay jars which I switch about every 2 months and I maintain a relative humidity of 55-60%, which is absolutely fine for long term storing and WILL NOT kill the tea, in fact the tea will age slower but clean and without any risk of mold, at all.
Sometimes it seems to me, the the clay jar method is doomed in America, probably because of one bad result with it..?
I heard of a lot of problems because of mold with the plastic box storage, especially when the tea is humidified in those boxes.

[faj]

Using this calculator, at a RH of 65%, there is no risk of mold at any temperature.
http://dpcalc.org/

There is no risk... if the temperature does not change. But in real life, RH will go up when temperature goes down until any humidity control has time to act.

Using the same calculator at 70F and 65RH, the dew point is 58F. If there is a drop in temperature to 58F and the humidity packs act too slow, RH will hit 100%. But you do not need to go that low for mold : at 58F, the calculator indicates there is risk of mold at 75RH. At 62F, risk of mold at 72RH. At 68F, risk of mold at 69RH. At 70H, risk of mold at 68RH, only 3 RH above nominal conditions. Make sure not to use a 70+RH humidity pack nor a slightly imprecise 65RH one. In any case, that sure feels like walking a fine line. There is a fair chance that normal temperature variations in many scenarios could cause risks of mold.

Saying there is no risk of mold at 65% is like saying there is no risk of fall at the edge of a cliff : it does not take a big departure from expected conditions for the statement to no longer hold.

[Rickpatbrown]

The interesting thing in this whole mater is that I have two pumidors that are humidified in the exact same way ... 2 half pint NaCl/sugar solutions in each pumidor. They are in the same place, experiencing the same temperature changes. Only one developed mold.

The differences are that the one that developed mold had way less tea in it and was not opened very often. It probably is sealed better, too. I removed the cooling components and sealed the hole with backing and aluminum foil. I think the other container gets fresher air.

The sample size is way to small for real conclusions. I may have just been lucky on my sheng pumidor.

Btw- these are the DYI salt packs that are described in the sticky of this forum. If these RH values are a problem, I bet a lot of people are using them. viewtopic.php?f=63&t=177

[Rickpatbrown]

Some pictures of the pumidors just to have some pictures in the thread ...

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[Rickpatbrown]

After a couple of days wringing my hands and revisiting some TeaDB articles and thinking more about the RH/Temp/dew point relationship ... I am fairly certain that the issue was that the temperature was too low at night. Or you can also say that the RH was too high for those temperatures. I'm really lucky that my main stash didnt get hit.

I'm going to look into setting up a thermostat or and arduino based system (depending on how many hours I want to devote) that can regulate the temperature around 75-80°F and keep RH at 68%.

I guess this has been. Good learning experience for me, with minimal loss.

I'm going to hose down the moldy pumidor with ethanol and see if I can recommission it for my pathetic shou supply.

[Iizuki]

There is no risk... if the temperature does not change. But in real life, RH will go up when temperature goes down until any humidity control has time to act.

Using the same calculator at 70F and 65RH, the dew point is 58F. If there is a drop in temperature to 58F and the humidity packs act too slow, RH will hit 100%. But you do not need to go that low for mold : at 58F, the calculator indicates there is risk of mold at 75RH. At 62F, risk of mold at 72RH. At 68F, risk of mold at 69RH. At 70H, risk of mold at 68RH, only 3 RH above nominal conditions. Make sure not to use a 70+RH humidity pack nor a slightly imprecise 65RH one. In any case, that sure feels like walking a fine line. There is a fair chance that normal temperature variations in many scenarios could cause risks of mold.

I totally understand the risk if the dew point is reached, but why is it bad to come close every now and then? Why do the mold spores care about relative humidity? Is it somehow easier to absorb moisture from air in cooler conditions? The amount of water doesn't change after all. Or maybe it goes down a tiny bit caused by the salt packs.

[26uk]

I totally understand the risk if the dew point is reached, but why is it bad to come close every now and then? Why do the mold spores care about relative humidity? Is it somehow easier to absorb moisture from air in cooler conditions? The amount of water doesn't change after all. Or maybe it goes down a tiny bit caused by the salt packs.

When RH is high, the material (say tea leaves) will absorb more water. A wetter leaf will allow mold to grow on it. So it's not the RH in the air but the water content in the material that allows mold growth.

When temperature drops, the air cannot hold as much water vapor. So even with the same amount of vapor, the RH is higher. RH is the absolute amount of water vapor divided by total water vapor the air can hold. So temp drop is the denominator decreasing. RH can change when numerator or denominator changes.

Hope this helps.

One key thing, your temp sensor might say 70F but another part of the pumidor (especially if additional heat added) could be 80F. Or even 60F. So localized conditions can be very different, so mold appears only in some places within the pumidor.