Light Absorption by Various Beer Bottle Glass  

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Courtesy of;

By Bradley E. Sturgeon, PhD, Monmouth College, Department of Chemistry,

Monmouth, IL 61462.

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Light can alter the properties of beer through a general process referred to as photochemistry; chemistry as a result of light ("photo").  To prevent photochemistry in a beer, beer is generally packaged in brown bottles to prevent photochemistry from occurring. Here we will show how the light is transmitted through different colors of beer bottles.

 

Shown in Figure 1, the black line represents the emission spectrum, or light. When this light shines on a bottle of beer, certain wavelengths of light pass through the glass and can potentially alter the beer properties via photochemistry. OK so far???....

 

When beer that is stored in a clear glass bottle that is exposed to light, the light is not shielded (the emission spectrum is unchanged, and as a result, all wavelengths (shown in black) will pass through the bottle and potentially alter the properties of the beer. Fair enough..

 

When beer stored in a green or blue bottle is exposed to light, some of the light is absorbed by the colour (green - green line; blue - blue line).

 

When beer stored in a brown bottle is exposed to light, the majority of light is absorbed (brown line), hence leading to a greater protection of the beer when compared to the clear glass bottle. EUREKA!!