Can You Carelessly Kill Your Scotch?

Can You Carelessly Kill Your Scotch?

by Neal MacDonald, Editor

We wanted to explore two myths pervasive in the spirits world:

1) Once a bottle is opened, long periods of time—even if stored properly—will affect the taste.

2) Exposing the bottle to sunlight will affect the taste… that’s why all the green and darkened glass.

Is this just snobby bullshit or is there some truth? Casual internet searches don’t offer much help beyond caution. “A distiller once told me it can affect the taste” (Refined Vices)… “Whisky is the least finicky… repeat sunlight will damage a whisky” (Drink Insider)… “Light and wide temperature fluctuations both serve to catalyze chemical reactions in volatile compounds and will eventually degrade those tasty esters and congeners in your whiskey” (Scotch Noob).

Damage? Affect? Catalyze the esters and congeners? It can sound a little bit like spooky bullshit along the lines of “bruising gin” or making sure your fish is served only with pink Himalayan sea salt. So we did the unthinkable: We bought two bottles of perfectly defenseless and innocent Glenmorangie 10yr Single Malt Scotch. We left one in its box and stored it in the cool, dark recesses of a basement. The other we resolved to punish with weeks of sunlight. These would be compared to a previously opened bottle of Glenmorangie 10yr that was now some 12 years past its open date. The goal: could regular people actually detect differences between these three bottles of otherwise identical scotch?

Glenmorangie should be a very good case. It’s of significant quality and moderate price. We know it to be a soft, approachable Highland malt with just a whisper of smoke and a good, clean taste. No heavy oak; no heavy smoke; the perfect scotch for testing the environmental effects of age and light. The marketing video backs up our sentiment, saying it has an “incredible softness and complexity of flavor” and a “beautiful bright pale gold color” with a “lovely soft texture” and notes of “vanilla, crème brulee, and citrus and floral fruit flavors.” All these things sound highly eligible to us for damage due to age and sunlight. In other words, let's see if sunlight can blow hell out of these flavors! 

Here are our testing candidates:

Pristine Glen: a bottle that was left untouched in its box until the day of the tasting. It was stored at constant ~60 degrees Fahrenheit once it came into our possession.

Punished Glen: a bottle acquired at the same time as Pristine Glen but was removed from the box, shorn of its label, and duct taped to the roof of an Illinois house in June. There it resided for 10 weeks soaking up vast amounts of sunlight, rained on several times, hailed once, and was even exposed to lightning and thunder on three separate occasions. At the end of Week 10, it was rescued from the rooftop and stored in the dark at 60 degrees right next to Pristine Glen. (We’re really sorry, Glenmorangie, but it was in the name of science.) 

Fatigued Glen: a bottle that was acquired on the discount rack of a grocery store in the year 2001. It was drunk to about 30% of its original volume, roughly 250ml. It was then forgotten in the back of the bar for the next 12 years until it was retrieved for this test. We guess it was a relatively constant 70 degrees Fahrenheit.

Our predictions were that there would be no real difference between the Punished and Pristine Glens but we might see some difference in the Fatigued Glen. We’re just not buying this "UV light damages whisky" stuff. And we set ourselves to blow this myth apart by testing them in multiple settings. 

Results follow:






Taste-Ice and Water

Pristine Glen

Light Gold.

The marketing video is correct. No caramel color and beautiful light colors.

Light Peat.

No Islay malt this… it’s an approachable rather than intimidating peat.

Sweet and Soft.

This is a light-footed, dancing sort of scotch. Again, very approachable.

Fruit and Heather.

A tiny bit of water really opens up the youthful flavors of this scotch… a great purchase to understand what Highland malts are.

Punished Glen

Washed Out!

Definitely a washed out gold… almost a light gold.

Skunk and Mold!

No joke. This was a clearly unambiguous finding. The aroma was absolutely vile. Beavis and Butthead would do better to describe these “flavor notes.”


This tasted like licking the moldy feet of the skunk we just smelled. Not kidding. We are stunned at how stark the difference is and the evil we’ve done to this defenseless scotch. 

Still Utterly Yucky!

Water, even at elevated volumes, did nothing to disguise the disgusting characteristics of the Punished Glen.

Fatigued Glen

Lighter Gold*

We think, think, we can detect a color difference but it’s very slight.

Lighter Peat*

Again, we think there’s the tiniest difference in the aroma… a somewhat lessened peat.


There’s a trend here… we think there’s a lessened flavor that we can detect. But it’s very slight. 

Fruit and Heather*

Water didn’t seem to hide the slightly diminished taste.

* NOTE: we couldn’t confirm the difference… see our “blind trials” below.


Myth Confirmed: Sunlight DOES Destroy Scotch Whisky (and probably anything else).

In scientific terms, these are completely “unambiguous results.” Our predictions were clearly wrong from the get-go. To our great astonishment, the 10 weeks on the rooftops utterly destroyed the poor Glenmorangie 10yr. We smelled it blind; we gave it to scotch snobs; we gave it to people who claim to hate scotch; we gave it to young and we gave it told; we gave it to men and we gave it to women; we gave it to people who claimed to have highly developed senses of smell and those who claimed to be scent-deaf. The results were universal and the results were emphatic: that Punished Glen was one of the foulest things anyone had come across.

We diluted the Punished and Pristine Glens 2:1 with water: no difference. We diluted the Pristine and Punished Glens in 4 parts Ginger Ale (we used a high-flavored, spicy ginger ale unfiltered Fresh Ginger Ale) with a twist of lemon and 3 ice cubes. And still… still there was a distinct aroma of skunk. We did at least dimly agree that after a third or fourth drink, there is probably less of a difference. Then, we went whole hog: 12 parts 7-Up to 1 part scotch and finally, there, the skunk was buried. No discernible difference. If you have a punished bottle, this is the highest and best use for it: bury it in dilutions of soda pop at 10 parts to 1 or greater.

One wonders if this is the result of temperature variation, or if one week was enough to do the damage, if darkened glass would have made a difference, or if slathering the bottle with sunscreen would protect it. Whatever the case, if you’re storing liquor where it has any exposure to daylight, move it immediately. We didn’t know better; the very night after this tasting we were scrambling to bury our bottles far away from any exposure to sunlight.

The Blind Trials.

The results were a little more ambiguous for the Fatigued vs Pristine Glens. We thought we could detect a difference… but was it real? Time for the Proof66 Blind trials. This involves a blindfolded participant where a coin flip determines whether Sample A (Pristine Glen) or Sample B (Fatigued Glen) would be offered to the blind participant, who would smell, taste, and then declare whether he or she thought it was one or the other over 10 trials. It’s a devilishly difficult test to pass.

Myth Busted: Time in a Previously Opened Bottle Does NOT Harm Your Scotch

Over the course of several 10x blind trials on the Fatigued vs the Pristine, all the participants felt that there was a clear difference and confidence in their selections was generally high at about 60%-70%. But the results showed otherwise.  Over the course of the many trials, the data showed exactly 50% right and 50% wrong declarations when guessing between Pristine and Fatigued. That is, our educated guesses were an exact match to raw, statistical chance. Based on that, we were deluding ourselves. There is no discernible difference tasting neat between Pristine and Fatigued Glen.

In summary, avoid sunlight but don’t worry about drinking your good whiskey quickly. We often get email questions asking if such-and-such label is “still okay” to drink. Not only is alcohol an excellent preservative making spoilage a very small concern but we’re ready to go on record and say that your old bottles are also likely to taste just as good as an un-opened bottle… or that the differences are so slight that they will escape notice. (At least up to 10 years… as soon as someone provides us with a 20yr old bottle of something, we’ll be happy to repeat the trial again.)  

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