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Behind The Still: How Sunlight Affects Bourbon


Behind The Still: How Sunlight Affects Bourbon


Written by Thomas Adams 
September 27, 2013

In the world of beer, exposure to ultraviolet sunlight has always been an important factor in taste and quality. Heavy exposure to UV rays can negatively impact the flavor of most beverages made with natural grains like barley, wheat, rye, and corn. But in the world of bourbon, sunlight is rarely a topic that’s discussed. However, direct UV light exposure on our favorite spirit does in indeed negatively impact its quality. But just how long does it take for bourbon to lose its luster when exposed to direct sunlight? We will test through an experiment to see if a mere 6 months of UV exposure can change the quality of a bottle of Bourbon.

100 ml bottles of Batch 26 on the shelf.

Setting up the Experiment: 5/20/2022

We chose a bottle of our flagship Black Button Distilling Four Grain Straight Bourbon from Batch 26 as our test subject. For reference, here are the specifications of our Four Grain Bourbon:

  • Mashbill: 60% Corn, 20% Wheat, 11% Malted Barley, 9% Rye 
  • Proof: 84
  • ABV: 42%
  • Age: 3+ years
  • 100% New York Grain 
  • Distilled and Aged in Rochester, NY

Experiment Baseline: 5/20/2022

All test bottles were stored in the same dark sample cabinet and at standard room temperatures. For our baseline, we measured color, aroma, and taste. We measured the color of our bourbon using a Standard Reference Method (SRM) Beer Chart. SRM charts are a standard for color testing beer and work for whiskey as well. Our control test measurement for Black Button Four Grain Bourbon at the beginning of the experiment was SRM 8.  

Standard Reference Method (SRM) Beverage Color Chart

Starting with two 750ml bottles of Batch 26 for this experiment, we broke one down into seven 100ml sample bottles. Then we set the first sample bottle aside to serve as our control to be opened in November at the end of the experiment. The remaining six 100 ml samples bottles were marked with the month they were to be tested ranging from June to November 2022. 

We placed the second 750 ml bottle of Batch 26 and the first control 100 ml sample bottle into one of our gift tubes to block out light. The remaining six 100 ml samples, marked by month, were placed on a windowsill in our office. Next to those bottles, we placed the tube with the unopened 750ml and 100ml control sample. Every sample bottle had the same environment, with exposure to light being the only variable. 

Each month we tested the 100ml bottle held in the tube against the marked monthly sample to see if we noticed any changes from the original taste and color notes observed at the beginning of the experiment. 

First Sampling: 6/20/2022

Well, experiments don’t always go as planned. Our initial expectation was that there would be subtle changes in the beginning with more drastic changes as the months went on. We were VERY wrong about that. Let’s talk about the damage just one month of direct light exposure did to the flavor and character of our test subjects. 

The notes on the light protected control changed a bit, but mostly stayed consistent. That isn’t surprising as the palate can perceive things slightly different from day to day. The real surprise was how quickly the light degraded the quality of the bourbon in the exposed bottle. It took all the wonderful notes from our Four Grain Bourbon and made it nearly undrinkable after only one month! We could have ended the experiment right then and there, but being curious types, we decided to give it another month. In the name of liquid science and due diligence, we wanted to confirm it wasn’t a fluke.

Second Sampling: 7/20/2022

It was no fluke! Just like the first sampling, the protected control bottle changed slightly but was mostly consistent. Holding true to the June light sample, the July light sample was equally unpleasant.  The flavor remained rough and rugged, with only hints of the character we know and love in our Four Grain Bourbon. The results were so dramatic that after only two months, we ended the experiment and made our conclusions.


The conclusions of this experiment are both clear and surprising. Clear in the sense that light obviously influences the quality of bourbon. But surprising as to how quickly it had that effect. We understand that this experiment exposed bourbon to a lot of direct UV sunlight which also imparted heat. But we strongly believe that overtime, even a small exposure to UV light will eventually change the character of bourbon, and not for the better. So, we strongly recommend that you store your bourbon in a dark and cool location. Or keep it in special packaging or a commemorative tube if your bourbon comes with one. Protect your bourbon so that every pour of choice is as exquisite as the last. Of course, we recommend that pour is one of our fine Four Grain Straight Bourbon Whiskeys. You can find them right here:


To shed some more light on the subject, check out this article in Food & Wine:

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