Your recent article on the exact nature of bubbles in beer and other beverages keyed an old memory. In Cleveland, during Christmas, one brewery used to bring out its holiday oddity for sale. They billed it as “the pale stale ale with the foam on the bottom . . . and the top!” There really was foam on the bottom and top. Sorry, can’t remember the brewery, nor can I vouch for the brewing process or the shape of the glasses. I was underage at the time.

Allan Weiser
Los Angeles, Calif.

About 50 years ago, it was my job to ferret out new uses and customers for a then-new wetting agent-detergent product. I sold a Coca-Cola bottler some to use in bottle washing. He was fighting mad on my return, because all the bottles so washed would gush out the Coke. My company lab decided it cleaned too well–probably removing a microscopically thin layer of soap inside the bottles that covered the tiny irregularities in the glass, which seeded the reaction. I don’t believe anyone ever pursued the cause-effect beyond that.

Harold C. Smith
Van Wert, Ohio

The story says, “the upward rush of bubbles pulls the liquid with it . . . .” This is incorrect. First of all, the bubbles are rising because they are being pushed upward by the greater pressure on their bottoms than on their tops. The reason the central column of liquid rises is because the column is less dense as a whole than the surrounding cylinder of liquid, since it has more bubbles in it. Therefore, it is displaced upward by the surrounding, more dense liquid (not pulled up by the rising bubbles). It rises for the same reason the bubbles rise.

George Van Vechten
Waterbury Center, Vt.