Mold growing on bottles in my wine refrigerator

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Geoff F.
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Mold growing on bottles in my wine refrigerator

#1 Post by Geoff F. » February 24th, 2019, 6:15 pm

I picked up a 166-bottle Smith & Hanks Dual-Zone Wine Cellar last summer, and quickly filled it with all the wine I wanted to age for the next 5-15 years (anything longer and I'd be more seriously considering off-site storage). Fast forward six months, and I've noticed substantial mold growth on the labels of several bottles, especially those that are on the back side of the cooler (front bottles were fine until just recently which is why it took so long to discover). My '98 d'Yquem label is completely obscured by mold at this point (in there since I got it), and even bottles I picked up in December have significant mold growth on them.

So I know to avoid it moving forward, what temperature/humidity range is most conducive to mold growth? I used to have smaller 16-20 bottle coolers set at 55F and those never developed any significant amount of mold. The zone that's set to 50F on this cooler (which is 55F in reality, per a real thermometer) is full of mold, while the other zone set to 65F has none.

How do I clean the mold off the affected bottles in a way that doesn't further damage them and inhibits future mold growth? I've heard of people using vinegar, bleach, or TSP - but I don't know what's best. Are there any special steps I should take to clean the fridge itself?
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Randy Bowman
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Re: Mold growing on bottles in my wine refrigerator

#2 Post by Randy Bowman » February 24th, 2019, 7:22 pm

Where are you located? I've yet to see mold in a refrigeration unit and I have 7 wine coolers plus three that wore out and were replaced. Mold usually forms when the container is too humid, (70 to 80 RH) and temperatures above 60 degrees. I occasionally will get some mold in one of my humidors if I don't use propylene glycol often enough to control it. If I get excessive mold in a humidor, I usually throw it away rather than dry it out, disassemble, sand and rebuild the box. (porous wood). All the mold needs to be removed.

If the refrigerator is lined with plastic or metal, I think you will have to go after it with a solution designed to remove/destroy mold, including drying time. You must also remove the mold on every bottle or it will spread again unless you correct the issue causing its growth. Unless the mold gets through the cork, it does nothing to the wine, just makes the bottle ugly.

I want to know how you got the mold growing so well.
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Chuck Miller
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Re: Mold growing on bottles in my wine refrigerator

#3 Post by Chuck Miller » February 24th, 2019, 8:10 pm

Too high humidity often combined with poor air circulation. Typically caused by a poor seal or other air leak. Also, leave a gap so your bottles aren’t touching the walls. Don’t block the fan.
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Geoff F.
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Re: Mold growing on bottles in my wine refrigerator

#4 Post by Geoff F. » February 24th, 2019, 8:15 pm

I'm in Seattle, but this is the first I've had this happen after previously using 4 different (smaller) wine coolers over several years here. My hygrometer just showed up, and sure enough, the RH in the cooler part of the fridge is a whopping 76% at the front, where bottles were less affected. Not sure what it's reading at the back, but the conditions are definitely ideal for mold. :(

Somewhere behind this lies a d'Yquem label:
Image

And there's even a spot of red mold growing on this bottle of Huet:
Image

I think the best course of action may be to clean all the bottles as you said, then scrub down the inside with a mold killing agent. I ordered rechargeable desiccant packets from Amazon, so those will go in on the back side where everything is more impacted. I'll also never buy another Smith & Hanks cooler, and stick to Wine Enthusiast or better.

Update: I did the math using an online calculator, and it looks like 55F/77RH is about the same as 65F/56RH, which is what I measured in the warmer section. So, it looks like the unit is keeping relatively constant absolute humidity across all zones rather than keeping consistent relative humidity in each. For some reason, they designed the unit such that the colder zone is above the warmer zone, and didn't effectively insulate the two from each other. I think what's happening is that warm wet air leaks from the warmer zone below, then meets the really cold air at the back of the fridge, and the relative humidity spikes to around 90% (which is what it would be for the same absolute humidity but at 50F). The mold problem only affects the bottom three shelves of the cold zone, and it goes away in the warmer top part. So, in addition to cleaning it all out, I'll now have to set both zones to the same temperature.

tl;dr - never cheap out on a dual-zone cooler, or if you do, buy tons of desiccant.
Last edited by Geoff F. on February 24th, 2019, 9:24 pm, edited 1 time in total.
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Re: Mold growing on bottles in my wine refrigerator

#5 Post by Todd Hamina » February 24th, 2019, 8:31 pm

Desiccant is always a great way to go from the start.
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Chuck Miller
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Re: Mold growing on bottles in my wine refrigerator

#6 Post by Chuck Miller » February 24th, 2019, 11:31 pm

I have never understood why one would use a Dual zone unit long term storage. For long term storage, you only need a single temp (approx 55 degrees F). The only reason I can figure out for a dual zone is to have things like Champagne at a colder that usual cellar temp for serving. But that is more easily accomplished by putting it in a refrigerator before serving.
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Kirk.Grant
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Re: Mold growing on bottles in my wine refrigerator

#7 Post by Kirk.Grant » March 5th, 2019, 2:14 pm

I had a problem with mold initially with my EuroCave. It was the stacking of the bottles and excess humidity from opening the doors too often. I cleaned them out with white vinegar, bought rolling shelves to replace the stacking part of the cellar and have had zero problems since. Good air circulation if key.
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Re: Mold growing on bottles in my wine refrigerator

#8 Post by Steve Slatcher » April 19th, 2019, 6:11 am

Chuck Miller wrote:
February 24th, 2019, 8:10 pm
Too high humidity often combined with poor air circulation. Typically caused by a poor seal or other air leak. Also, leave a gap so your bottles aren’t touching the walls. Don’t block the fan.
That just about covers it, but in a few more words on a couple of points... Check the seal round the door. And it is the wall containing the cooling elements that can cause most damage - the reason is that condensed water runs down that wall and should not be allowed on bottles.

I had a (much less impressive) problem with mould, and believe it was pulling all the bottles forwards a bit that solved it. I wiped bottles and affected shelving with a weak bleach solution. It may not be ideal from a TCA point of view, but it worked for me.

I would not tinker by adding stuff to dehumidify. Any air getting in will increase the humidity, but the fridge will have an air intake that should be designed to let in just the right amount to get the humidity right and maintain air circulation.

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