We set out to answer a question that does not seem to have a good answer: “What happens to bourbon when stored in different real world conditions and fill levels over time?”

We went into this tasting thinking the results might be a simple extension of our 6 month tasting results. However, that was not the case. The additional 6 months changed the bourbon to an extreme we were not anticipating. What follows is a summation of our opinions which were confirmed blindly by two different tasters.

Read Part 1 of our Bourbon Storage Experiment for the complete details of the setup of the experiment. Read our 6 Month Tasting Results for a summary of tasting results at the 6 month mark.

How We Tasted:

• The samples were all moved from their storage locations to a common location 2 days prior to tasting in order to allow them to acclimate to room temperature.
  
  

• There were 2 tasters - Nick and Eric.
  
  

• We tasted blind in sets of 2-3 samples at a time, as any more would have been too many to compare at once.
  
  

• We purposely varied the blind sets between the 2 tasters so that different direct comparisons could be made. Once complete, we cross-referenced our notes in order to piece together the findings so they could be presented here.
  
  

• Nick re-tasted twice after the initial tasting in order to directly compare the full fill refrigerator sample to the full fill closet sample.

For this tasting there were two of us blind tasting different sample flights. The results surprised us because we had anticipated somewhat of an extrapolation of data from our 6 month tasting, but instead observed much more extreme differences.

Most evident, the direct sunlight stored ⅓ fill sample was downright bad and the worst overall, exhibiting taste characteristics of rotten apples, paint thinner, and rubber balloons. These characteristics were less extreme as we moved to the ⅔ and full fill direct sunlight samples, but even they were obviously off-tasting with the ⅔ fill on its way to a similarly bad flavor profile. I will point out that during the summer months of June, July, and August right before this tasting I noticed the temperature was a bit higher at the location the samples were stored. During clear sunny days the samples felt warmer to the touch than the ambient air at their location, which I’ll refer to as the “hot car effect.” This raises a question - did the interior air space (and bourbon) in the sample bottles heat up to a significant extent just as a car does on a hot sunny day, and if so, how did this differ between the varying fill levels? Furthermore, what effect did this temperature change have on the change in taste of the bourbon? We may test this question more specifically, but I will also point out that the sample stored in the amber bottle in direct sunlight (which was at ⅔ fill) did not experience the same extreme change in taste as it's clear counterpart. In fact, it was just slightly off-tasting by comparison.

Unfortunately, I do not have any data measuring the temperature changes inside the bottles, and it is possible that the amber bottle kept the bourbon inside at a lower temperature than the clear bottles just as tinted windows help reduce the energy that enters a car minimizing the hot car effect. This is one notable piece of information that will have to be further evaluated in order to better understand the effects of temperature change on bourbon. Despite this, we can definitively say that sunlight caused damage, we just don’t know what extent of the damage was caused by the sun’s rays permeating the bourbon versus its resulting increase in temperature within the bottles. For the time being, this study provides some interesting information on the topic.

As for fill level, we noticed an opposite effect from what we had noticed at 6 months. At 12 months we noticed greater fill level yielded better bourbon. This was consistently noticed by both tasters and for all three storage locations, though it was not nearly as extreme of a difference with the refrigerator and dark closet samples as with the direct sunlight samples. As for the direct sunlight samples, the greater fill level proved to significantly mitigate the negative effects, though the full fill direct sunlight sample was still noticeably off-tasting.

Finally the dark closet versus refrigerator samples which, like all samples here, were tasted at room temperature. Between the two of us we generally found the refrigerator stored samples to have more character than the dark closet stored samples, though this difference was minor. I went back after the initial tasting and tested the full fill dark closet sample against the full fill refrigerator sample a few times to be sure of this. It turns out I preferred the refrigerator sample every time by comparison. Also notable was the dark closet sample exuded more alcohol in the sip, while the refrigerator sample seemed to allow the rich flavors to show through more intensely. That said, they were still markedly very similar overall.

*I will note a word of caution here on refrigerator storage. We’re using sample bottles with tightly secured screw caps in order to zero in on the effects of storage location and fill level - NOT the effects of a faulty or dried out cork. Unlike wine corks which are pressure fit into wine bottles, whiskey corks form a much looser fit. If a cork dries out a bit, air could find its way in and spoil your whiskey in a relatively short time. For that reason, storing corked whiskey bottles for a long period of time in a refrigerator could increase the risk of cork failure because the interior of refrigerators is generally drier than regular air, potentially sucking the air out of a loosely fit cork more quickly. We plan to explore this further in another experiment, but for the time being be cautious of storing your corked whiskey bottles in the refrigerator. That said, if you’re someone who just prefers your everyday drink cold, storing it in the refrigerator probably won’t hurt anything if you drink through it relatively quickly and it’s an easily replaceable everyday bourbon.

‍What We Noticed:

• The flavor variety was much more extreme this tasting than it was at 6 months, with more noticeable differences between the storage locations and fill levels.
  
  
• Generally speaking, the direct sunlight samples were worse than any of the dark closet or refrigerator samples.
  
  

• The full fill refrigerator stored sample was the favorite between us, though it was notably very similar to the full fill dark closet sample.
  
  
• We both agreed beyond any doubt that the ⅓ fill clear sunlight sample was the absolute worst overall. Though we were still able to drink it without spitting it out, it was characteristically “bad” and significantly worse than any of the other samples.
  
  
• The refrigerator stored samples tasted very similar to the dark closet samples with the refrigerator samples demonstrating a bit more richness of flavor than the dark closet samples. This difference was so subtle further tasting was required, though this did confirm the initial observations.
  
  
• In each condition more fill (less air) generally yielded a better taste - full fill > ⅔ fill > ⅓ fill. As fill level decreased, the flavors in the refrigerator and dark closet samples became increasingly muted. With the direct sunlight samples, the flavor became increasingly worse as fill level decreased. This is the opposite of what we noticed at 6 months.
  
  
• The amber bottle stored in direct sunlight significantly helped mitigate the negative effects of sunlight, though it did taste slightly off. When compared directly with the clear drink down direct sunlight sample the off taste was very difficult to pick up on, as it seemed to taste normal by comparison.
  
  
• The samples stored in direct sunlight in clear bottles lost a good deal of color, with the ⅓ fill direct sunlight sample losing the most.

12 Month Snapshot: Color Change

Dark Closet 1/3 Fill VS Direct Sunlight 1/3 Fill