What indicates that a glass is beer clean when performing the sheeting test?

A glass is considered beer clean when droplets run off in sheets, which indicates there's no residual oil, grease, or detergent that would affect the beer's head retention and flavor release. The sheeting test involves rinsing the glass with water; if the water forms beads and does not sheet off smoothly, it suggests that the glass is not clean enough for serving beer.

When droplets run off in a continuous sheet, it demonstrates that the surface is free of contaminants that would interfere with the proper formation of the beer’s head and overall presentation. A clean glass will allow for optimal carbonation and retention of aromas, enhancing the drinking experience.

In contrast, if there are water spots, the surface might still have residues affecting how beer interacts with the glass. A frosty glass usually results from condensation and does not imply cleanliness for serving beer. Similarly, a completely dry glass does not ensure that it is free from residues; the sheeting test is the reliable method to confirm true beer cleanliness.