When exposed to sunlight for even an hour, beer will undergo a chemical reaction that creates an organic compound called 3-methyl crotyl mercaptan. This compound can give your beer a "skunky" flavor similar to the commercial example Heineken. For this reason, always store the carboy in a dark closet or cover it with something. But what should you cover it with?
- Cut out a piece of brown corduroy to be about 36 x 24 in.
- Sew a straight seam up the length, making it about 34.5 inches (the carboy I'm using is 34 in. in diameter)
- Make a pocket along the top and the bottom and push elastic thru each (less elastic in the top and just bunch it more),
- Sew those up and VOILA! Done.