A- The reserve stock of bottled beer should be stored in a cool, dark place. He must never use full bottles for display purposes, where they will be exposed to the sun or strong daylight. Bottles with clean labels filled with water may be used as dummies for display purposes. Beer exposed to light will become light-struck. Light-struck beer assumes first an off-taste and then becomes hazy and develops a sediment. The speed at which beer becomes light-struck depends upon the intensity of the light. Beer must never be exposed to the direct rays of the sun which will noticeably affect it in a few minutes."
"[The bottle manufacturers] admitting that sunlight is hardly good for beer ... contends that very few dealers or consumers are foolish enough to expose beer to the direct rays of the sun. (Shopkeepers put dummy bottles in their windows)."
“Lightstruck - While this defect is well known in both odor, taste and
origin, it is sometimes not realized how little exposure can produce a
noticeable lightstruck character. The
wavelength of light causing this photochemical spoilage is 550 nm and below.* Bottled beer can become lightstruck in less
than one minute in bright sun, after a few hours in diffuse daylight and in a
few days under normal fluorescent light.”
Practical Brewer, Master Brewers' Association of the Americas 1977
* i.e., not just “UV light” [10 nm to 400 nm] as the modern beer geek myth has it.
"The reserve stock of bottled beer should be stored in a cool, dark place."
"Beer is highly susceptible to light, and we might add, light from any source. In sunlight, the reaction is almost immediate. The ultraviolet part of the light spectrum breaks down the sulphur containing molecules, forming highly odourous mercaptans and other sulphurous compounds. A customer complaint on this subject cannot possibly be mistaken, as a most objectionable odour and flavour is present."
"A surprising fact is that beer in the regular amber bottle will begin to be noticeably 'lightstruck' within about two minutes, while beer in a clear glass will begin deteriorating within 30 seconds."
---An Introduction to the Brewing Process: Comments on Bottled Beer
R.G. Black, revised by G.J. Kitz