What should you check to assess the cleanliness of glassware without beer?

To assess the cleanliness of glassware without the presence of beer, performing the sheeting test is the most effective method. This test involves rinsing the glass with water and observing how the water behaves on the surface. If the glass is clean, the water will sheet off smoothly and uniformly. Conversely, if there are residues or contaminants present, the water may form beads or not spread out evenly, indicating that the glassware is not properly cleaned.

The sheeting test is a reliable indicator because surface contaminants can significantly affect the beer's appearance and aroma, particularly head generation and retention. Thus, ensuring that glassware is clean is essential for delivering an optimal beer-drinking experience.

The other options do not effectively assess cleanliness in the same way. For instance, checking for bubbles clinging to the sides might indicate cleanliness but can also be influenced by the carbonation of the beer itself when it is poured. Checking for head retention is not applicable without beer being present and would provide an unclear assessment of cleanliness. Inspecting for color does not directly relate to cleanliness, as the appearance and color of the glass do not indicate whether residues or oils are present.