Temperature Fluctuations In Passive Cellars

[Pat_Burton]

Some interesting thoughts here. I think there is some misunderstanding of the nature of cork though. Cork is indeed a porous material but, as previously stated, can create a perfect seal. Cork is made from bark and bark does allow for gas exchange in a living tree. However, corks are cut and inserted into wine perpendicular to the pores, which run in a single direction. Take a look at a quality cork next time you open a bottle and you’ll see that the pores run cross-wise, not length-wise. If there is gas exchange occurring, it is far more likely occurring between the cork and the bottle, not through the cork.

In terms of the effects of temperature fluctuations on wine, I can only offer my own anecdotal evidence. I store wine in three places, two of which are temperature controlled and one of which is a rack in a bedroom of my house. The bottles in this rack experience daily temperature fluctuations roughly equivalent to what I allow the house temperature to fluctuate at (the minimum is typically 5 degrees F per day). In the fall and spring, we open the windows throughout the house and temperatures fluctuate greatly, sometimes by as much as 20 degrees in a single day. Summer time highs can reach 80 in this room and fall nighttime lows can reach the mid 50s. While this rack is intended for near-term drinking, I’ve had bottles stored in this rack for over four years before I get to them. I haven’t done a side by side comparison, but I have tasted identical wines stored in this manner and from my offsite within the same week. I have yet to notice a difference. I have also not observed any difference in the elasticity or dryness of corks stored in the temperature fluctuating rack.

[Dav1dZ]

@Al Osterheld

Alan, you ignored the effect of the change in temperature on the volume of the gas in the headspace. Back of the envelope, that roughly doubles your numbers. And I think that’s enough to cause problems, especially if we’re talking about the gas finding a weak spot to pop a leak, rather than pushing the whole cork out.

The gas volume in the headspace shrinks when the temperature rises, because the liquid compresses it. Maybe you meant the rise in pressure? That’s roughly a 10% effect with temperature rise from 50F to 100F, (delta-T)/T with T measured from absolute zero. The pressure rise is dominated by the liquid expansion, basically because there is so much more of it, and because it is much less compressible.

-Al

Yes, my goof - I meant rise in pressure.

[Peter_Cargasacchi]

If cork forms a perfect seal, how does wine oxidize in bottle? Tin lined screwcaps form a perfect seal. Saranex lined screw caps allow a minute amount of gas exchange. Corks, with a great deal of variability between corks, allow greater gas exchange than the technical closures. I have tasted wines in cork that in passive cellars that were “too warm” (high 60s in summer) but with no daily temperature fluctuations, ( a static temperature,) age/matured and were fine, Whereas wines subject to daily temperature swings of at least 10 degrees were oxidized within a period of years. That’s been my experience aInd the only mechanism for accelerating oxidation is the daily contraction and expansion of the liquid as it relates to the movement of gas through the closure.

This seems like a great experiment. You would need to use a technical closure with known and uniform permeabilty. You bottle a wine with known volatile acidity and Sulfur then place the wine in a conditions of different daily temperature range fluctuations, and a range of static temperatures from 55 f. to 80 f. in 5 degree increments. Then measure the volatile acidity periodically. No one has done this experiment? That seems odd. Its an obvious experiment, someone has done it.

[GregT]

Peter - again, it is not necessarily through the closure, although because of imperfections in cork, that may be the case. In a perfect cork however, it can be into and out of the cork itself. The liquid doesn’t contract in reaction to the temp changes nearly so much as the air in the headspace. That looks for an escape. There are four options. One, go nowhere because it’s locked into a small space and all it can do is increase pressure on the liquid and the bottle and the cork, but not enough to displace any of those things. Two, diffuse into the liquid. Three, get into the cork, and four, go through the cork.

And then we have to ask, is there a capsule and what role does that play?

There are precious few studies on this but the only ones I’ve seen suggest that the air diffuses into the liquid and into the cork itself, which of course conflicts with the popular notion that it goes through, rather than into, the cork. So the oxidation can take place with the oxygen coming from air beaten into the wine by bottling, the air in the headspace forced into the wine by corking, and the air diffusing out of the suddenly compressed cork cells.

In 1933 there was a paper published that described their measuring the oxygen that diffused out of the cork and into the wine. It took about three weeks for equilibrium to be reached. They wrote in conclusion that “clearly the initial air has come out of the compressed cork cells near the inside end of the cork and not “through” the cork.” It’s a study in a book by Gordon Robertson called Food Packaging and Shelf Life: a Practical Guide.

As far as back in the 1880s they analyzed the gas found in the cork cells and determined that it was just air.

I don’t have them but I did see some studies from Bordeaux where they measured air transport through cork and they determined that the best cork allowed no more air passage than a synthetic seal whereas the worst cork allowed quite a bit. It was impossible to predict what a specific cork would do and if I recall, that had an effect on what the winemaker would elect to do - sulfur for the highest or lowest or average probable air transmission.

Then there were some more studies from Portugal, desperately attempting to save the cork industry, showing that cork permeability for gases was drastically decreased after cork is exposed to alcohol and/or water and also, interestingly, that the diffusion had little to do with whether the bottle was placed on the side or upright.

[Greg_Malcolm]

@Pat Burton

Some interesting thoughts here. I think there is some misunderstanding of the nature of cork though. Cork is indeed a porous material but, as previously stated, can create a perfect seal. Cork is made from bark and bark does allow for gas exchange in a living tree. However, corks are cut and inserted into wine perpendicular to the pores, which run in a single direction. Take a look at a quality cork next time you open a bottle and you’ll see that the pores run cross-wise, not length-wise. If there is gas exchange occurring, it is far more likely occurring between the cork and the bottle, not through the cork.

In this instance, the liquid seal is only that – a seal that prevents the movement of liquid. It does not prevent the movement of gases. The movement of gases across the cork is a function of the permeability of the specific gaseous molecule in the cork and the driving force for permeation, which is the partial pressure difference between the inside and outside of the bottle for the specific gas. (As somewhat of an aside, gases also permeate through the glass bottle; however, the permeation rate is so low it is negligable – but it is not zero.)

[Peter_Cargasacchi]

Worth repeating also that the solubility of gases in liquid decrease as temperature rises snd solubility increases as temperature decreases. Which facilitates to some degree the exchange of gases from the liquid/wine to the cork. Temperature has other effects on the system and contributes to internal pressure beyond volumetric expansion and contraction.

[Peter_Simpson]

@GregT

The liquid doesn’t contract in reaction to the temp changes nearly so much as the air in the headspace.

Sorry Greg, and maybe I’m misunderstanding your post, but as written this is not correct. The gas equation is PV=nRT with pressure and temperature measured in absolute terms.

If you take a gas space at atmospheric pressure (14.7psia) and heat it from 515 to 535°A (55 to 75°F) the pressure will increase to 15.3psia (0.6psig).

But if 750ml of water are heated thru that same 20°F its volume will expand by 1.6ml. The liquid expansion would thus reduce a typical 6ml headspace to 4.4ml and cause the gas pressure to increase to 19.9psia(5.2psig).

So thermal expansion of the liquid had eight times greater effect on pressure than the gas.

Carg’s point about gas solubility changing with temp is very interesting, if headspace gas is less soluble as temp inceases it too would cause pressure to increase. I’m starting to wonder why we don’t have corks being pushed out all over the place.

[Peter_Cargasacchi]

The system is more dynamic thsn just thermal expansion contraction. Throw in oscillating gas solubility, increasing then decreasing on a daily cycle, and it enhances the effect of temperature changes on liquid volume, by 1 also affecting pressure 2 making the wine a more efficient reservoir for gas exchange. The bottle on a minute level is breathing, and the higher the daily temperature fluctuation, the faster the rate of oxidation. Distinct from the effect of prolonged warm temperature.

[Alan_Rath]

@Peter Cargasacchi

The system is more dynamic thsn just thermal expansion contraction. Throw in oscillating gas solubility, increasing then decreasing on a daily cycle, and it enhances the effect of temperature changes on liquid volume, by 1 also affecting pressure 2 making the wine a more efficient reservoir for gas exchange. The bottle on a minute level is breathing, and the higher the daily temperature fluctuation, the faster the rate of oxidation. Distinct from the effect of prolonged warm temperature.

Peter, I agree with the higher temp leading to faster development (I can’t sign on to oxidation), but I just don’t agree with any of the other. There are certainly truths to what you are saying, I just don’t believe they rise to the level of having a noticeable effect on the development of a wine. I suppose I’m hand waving in my response to your hand waving but I think you’re making it more complicated than it really is. To put it simply, it’s a closed system - if it weren’t, the water would diffuse out through the cork, just as you postulate air does, back and forth, on a regular basis, and you wouldn’t have any wine left after a few years.

[Pat_Burton]

@Greg Malcolm

@Pat Burton

Some interesting thoughts here. I think there is some misunderstanding of the nature of cork though. Cork is indeed a porous material but, as previously stated, can create a perfect seal. Cork is made from bark and bark does allow for gas exchange in a living tree. However, corks are cut and inserted into wine perpendicular to the pores, which run in a single direction. Take a look at a quality cork next time you open a bottle and you’ll see that the pores run cross-wise, not length-wise. If there is gas exchange occurring, it is far more likely occurring between the cork and the bottle, not through the cork.

In this instance, the liquid seal is only that – a seal that prevents the movement of liquid. It does not prevent the movement of gases. The movement of gases across the cork is a function of the permeability of the specific gaseous molecule in the cork and the driving force for permeation, which is the partial pressure difference between the inside and outside of the bottle for the specific gas. (As somewhat of an aside, gases also permeate through the glass bottle; however, the permeation rate is so low it is negligable – but it is not zero.)

Your statement is true of all solids and isn’t specific to cork. I don’t understand what your point is.

[Greg_Malcolm]

@Pat Burton

I don’t understand what your point is.

That gases are moving through the cork.

[David_Raccah]

I cycle my unit on and off every 12 hours to save energy (and because the fan on my Kenmore unit starts to run nonstop if I leave it on too long), and it causes my cellar to go from 57 to 59/60F over a 24 hour period.

I have never been concerned about this as a “spike”, as I assume the wine temp remains around 58 the whole time.

Thoughts?

Hello,

First of all, I read this entire thread and I understand this was for a passive cellar thread and I understand I am reviving an old thread - probably TWO bad ideas - please excuse me in advance, but this question was not really answered in the thread and I would love to know the answer.

I am facing the same issue with a 3-degree max fluctuation per day but more often a 1 or 2-degree fluctuation. My cooler, cellar Pro, is one of the worst ideas I ever did, it has so many stupid idiosyncrasies that it drives me nuts. I have spoken with them many times - anyway, pet peeves aside. I turn off my cooler during the peak hours and during the night as it makes a MASSIVE racket and power usage is bad during certain hours in Cali.

So, when it goes back on, even after a 100+ degree day, the max I see is a movement from 58 to 61, again, mostly to just 59 or 60 during lower temp days. Is this 8-hour fluctuation an issue? Meaning the temp rises 3 degrees max over 8 hours and then I bring it back down, then it goes up again a degree or two and I bring it back down, all within a 24 hour period.

TIA and again my apologies for probably breaking many thread rules, just liked the context of the thread as I had the same question.

[DanielP]

David,

I would try measuring changes in the fluid temperature as the temperature of the wine will change much more slowly than the air temperature. Fill up an empty wine bottle with water and track the temperature changes over the course of the day with a digital thermometer. Of course, I don’t actually know what’s considered an acceptable temperature swing, but if you have a reasonably full/packed cellar, I would be surprised if the fluid changed more than a degree.

[David_Raccah]

David,

I would try measuring changes in the fluid temperature as the temperature of the wine will change much more slowly than the air temperature. Fill up an empty wine bottle with water and track the temperature changes over the course of the day with a digital thermometer. Of course, I don’t actually know what’s considered an acceptable temperature swing, but if you have a reasonably full/packed cellar, I would be surprised if the fluid changed more than a degree.

I am sorry if that was not clear - that is the cellar pro temp using a wine (in water really) probe. So, yes, the wine temp (in my case water temp in the probe bottle) moves up to 3 degrees (only happened once), but mostly 1 or 2 degrees by early morning and/or early evening.

[Andrew_K]

Turning off your cooler for that much time each day sounds like a bad idea. With my bottle probe I only see about 0.5 degree fluctuations in liquid temp with the unit cycling on and off as normal.

[JLuch]

David, I am not as scientific as the previous posters on this thread, but all the literature I have read on passive cellars (as I have one myself) and ideal climate for wine storage, a key takeaway has always been this: Seasonal changes seem to be acceptable, 52 winter to 62 summer as an example, assuming that the temperature on a winter day is around 52-53 (air temp) in the cellar for the entire day. Alternatively the temperature variation on a particular bottle is within a 1 degree throughout the day. My cellar, as an example, changes +/- 8 degrees over the course of the year, but the daily temp stays flat and only deviates +/- 1 during transitional months when soil temps in New Jersey rise and fall (spring and fall).

That being said, I don’t know how much harm a 3 degree daily change in fluid temperature will do to a wine. I think if it were me, I would see if there was a feasible way to get that number closer to 1 degree daily.

Sorry for the less then stellar answer, but hopefully this helps.

[Alan_Rath]

So, when it goes back on, even after a 100+ degree day, the max I see is a movement from 58 to 61, again, mostly to just 59 or 60 during lower temp days. Is this 8-hour fluctuation an issue? Meaning the temp rises 3 degrees max over 8 hours and then I bring it back down, then it goes up again a degree or two and I bring it back down, all within a 24 hour period.

TIA and again my apologies for probably breaking many thread rules, just liked the context of the thread as I had the same question.

No apology necessary, tacking on to old threads can be fun.

I would kill to have your cellar, and that temperature stability. If it were me, I wouldn’t think twice about it.

[Carl_Steefel]

As you can see, lots of opinions.

Here are some more. For some reason people seem to think that the speed of the fluctuation matters. There is no evidence that I know of to support that. It’s the fluctuation, whether over a few days or months that matters.

Then there are other people who think that the seasonal shifts are somehow more “natural” and are the way you’re supposed to age wine. I’m not aware of any science supporting that either.

I am not completely sure this is true, since the argument about more sudden (short lived) fluctuations is that they result in strong gradients that may drive the problematic fluxes of liquid and counter flux of oxygen. More gradual changes will obviously heat up the wine even more (or cool it down more), but the local gradients that the fluxes are proportional to will be larger if the time scales for the same fluctuation are shorter.

This would be a completely separate topic than the long term variation, which does not drive fluxes so much as simply age the wine more rapidly over the longer seasonal period.

[Alan_Rath]

I wish everyone would just relax on the worry about temperature “fluctuations”. There is nothing in chemistry that depends greatly on temperature fluctuations (unless, of course, you are near some boundary like freezing or boiling). Also remember that most relationships that depend on temperature use Kelvin. So a change from, say, 60 to 65 Farenheit is actually 288.7 to 291.5, which is a change of just under 1%. Stop worrying about temperature fluctuations.

[Carl_Steefel]

I wish everyone would just relax on the worry about temperature “fluctuations”. There is nothing in chemistry that depends greatly on temperature fluctuations (unless, of course, you are near some boundary like freezing or boiling). Also remember that most relationships that depend on temperature use Kelvin. So a change from, say, 60 to 65 Farenheit is actually 288.7 to 291.5, which is a change of just under 1%. Stop worrying about temperature fluctuations.

Not, not chemistry, unless you consider Onsager’s Irreversible Thermodynamics as “chemistry”. Fluxes driven by chemical potential gradients, or pressure gradients, …