humidity in cellar

As long as you keep humidity over 50%, variation shouldn't matter. I think 75% is the maximum, which you don't want to go over due to potential mold and ruining labels. That being said, even with short periods of time over 75%, you should be fine. The other thing you might or might not realize is that your cooling unit will also act as a dehumidifier. Therefore, you'll likely be ok even in a fairly humid environment. I bought a relatively inexpensive Lacrosse thermometer with humidity and put the sensor in my stand-alone cellar. I recommend doing the same with a walk-in cellar.

quote:

Originally posted by Jack in MS:
As long as you keep humidity over 50%, variation shouldn't matter.

I have a slightly different question on the same subject.

Like Perlasteve I have also recently created a new underground cellar. Mine exists for the purpose of storing wine and other things which have to be kept dry. Just as the builder went to insulate the walls, we found a lot of moisture accumulating on the floor, which was a mystery. Then I went to check the level of the water in our nearby well which hasn’t been used for many years. The level was surprisingly high and I thought that maybe surplus water was being drawn up by the walls of the cellar and was being deposited on the floor. So I decided to install a pump in the well in order to keep the level down. It worked. Great! Now the bad news.

That was 3-4 months ago. Since then, the humidity in the cellar has been continually decreasing from originally 70%. At first this must have been due to the plaster drying out, but now the humidity has continued to sink below 30%. I never thought that this would be possible in an underground cellar, because upstairs in the living quarters it is regularly around 50% or higher. The dryness in the cellar is presumably due to the very porous sand and gravel under the house which is built near to a lake, plus the good insulating work of the builder (who also installed an extractor fan) and my initiative in fixing the well.

Now my question is, what is the lower humidity tolerance of natural corks? Most of my wine is in the cooler (which isn’t humidity controlled), but some of it is in open racks on the floor. All the bottles are either screw caps (white and rosé) or natural cork with foil covers (red). Now I suppose that the purpose of the foil covers is to protect the cork as well as to make the top of the bottle look nice. But does this protect against low humidity when the bottles are stored horizontally?

I hope I don't have to move the reds in the open racks out of the cellar, since the cooler is full. Note that these reds are mainly newly corked (2008 and 2009). Or can I keep them for another year at low humidity until there is space in the cooler?

Interesting question.

Before use, the corks are ideally kept at 50 to 70 pct relative humidity - less than 100% saturation, and the moisture content is kept to 5 to 8% by weight. Most people want to keep the wine cooler the same. The bottle will have 100% humidity and in theory, keeping the outside humidity roughly at the same humidity level that the corks experienced before insertion will keep them roughly in the same condition - i.e. plump and fully expanded to perfectly seal the bottle.

That's the theory anyhow.

Over 70% may provide enough moisture for mold to grow - so wrap your bottle in plastic if you care about the label.

Under 50% is thought to be the lower threshold after which the corks start to dry, but that's not completely understood. It's really hard to find much science on this issue. Too little humidity would dry one end of the cork, possibly causing the wine in the bottle to go through and evaporate, at least if the bottle is on its side. The problem is that everyone says this, all the bloggers and "experts" claim it, and there's precious little science to back it up. If you've got a capsule on the bottle, it's hard for me to understand exactly how the moisture gets through the metal or plastic in the first place.

In any event, I'm not happy to experiment on my own wines - I'd love it if someone else ran these experiments.

So you might turn off the extractor fan for a start. Maybe turn off the pump or run it less often too. According to conventional wisdom, at 30% you're way below what you want.

quote:

Originally posted by GregT:
Under 50% is thought to be the lower threshold after which the corks start to dry, but that's not completely understood... Too little humidity would dry one end of the cork, possibly causing the wine in the bottle to go through and evaporate, at least if the bottle is on its side...
If you've got a capsule on the bottle, it's hard for me to understand exactly how the moisture gets through the metal or plastic in the first place...
According to conventional wisdom, at 30% you're way below what you want.

Interesting remark you make about the capsule (aluminum foil cover over the top of the bottle). In Switzerland practically all local and imported reds are naturally corked plus a foil cover. In my collection of 120 bottles imported from many countries only 1 bottle (a Casanova) is without a foil cover. Also interesting is the fact that practically all foil covers have 2 or 4 small holes over the cork, as if to say, the cork has to breath! I find this strange - either you want to protect the cork or you don't. The only exception I have is a Smith Haut Lafitte which does not have any holes in the cover.

I have now placed a tray of water right under the necks of the stack of bottles, in order to increase the humidity exactly where the corks are, in case they get thirsty.

john - the holes are interesting and I've seen them too, but as you point out, not in all capsules. I guess it's what you call hedging your bets, i.e. just in case the cork transmits atmospheric oxygen, let's leave some holes. I guess that's what you call hedging your bets?

Of course, some capsules are plastic and that's another factor - we know what happens when you put a plastic bag on someone's head.

But we have another factor to add. Let's say there was a drop of wine on the outside of the cork for whatever reason, or some moisture under the capsule, or on it, and a bit of mold grows. In fact, a little mold on the cork is pretty common. So does that affect the oxygen transmission rate? And does that affect the drying rate?

Unfortunately, it's really hard to find good science on the issue. Most of the info is based on anecdotes or tradition. I've been in many cellars where there is extreme humidity - most were carved into mountainsides and sometimes there's even dripping water and mold everywhere. It doesn't affect the wine. But I can't remember being in a place that was extremely dry except my Uncle's house in Napa. He was on a mountainside and carved a cellar space out of the rock. It was so dry he had drip irrigation on his flowerpots. Cases of wine in the cellar and no problems for many years. In fact, a lot of his cases were stored upright.