When beer is poured, what is an indicator of a beer-clean glass?

A beer-clean glass is essential for ensuring that the beer’s flavors and aromas are properly showcased. An indicator of a beer-clean glass is lacing and proper head formation, which is the correct response.

When a beer is poured into a clean glass, it should produce a stable, persistent foam (the head) that holds a good amount of bubbles. As the beer settles, this foam clings to the sides of the glass, which is known as lacing. This lacing indicates that the glass is free from any oils, detergents, or residues that could interfere with the beer’s carbonation and appearance. Proper head formation contributes to the beer's aromas and enhances the drinking experience.

Other options suggest less desirable characteristics for serving beer. For instance, bubbles forming only at the bottom indicates a glass that may not be entirely clean, as clean glass should promote even carbonation throughout the beer. Crumbling foam and a flat appearance with no bubbles suggest that the beer is oxidized, stale, or that the glass has not been appropriately cleaned, which negatively impacts the overall presentation and drinking experience.