In manually washing a beer glass, what should be avoided in the detergent used?

When manually washing a beer glass, it is essential to avoid using fat, petrol, or oil-based cleaners because these substances can leave residues that affect the beer's flavor and appearance. Such residues can create a film on the glass, which may hinder the formation of a proper head on the beer and impact the overall sensory experience. Beer is highly sensitive to contaminants, and using cleaners that are not specifically designed for glassware can lead to a negative drinking experience.

In contrast, fragrance-free soaps and dishwashing liquids with natural ingredients are generally safer options, as they are less likely to impart unwanted flavors or leave harmful residues. While bleach-based cleaners are also not recommended due to their strong chemical nature and potential to leave a taste or odor, the most critical consideration when washing a beer glass is to ensure that no fat, petrol, or oil residues remain, as these can significantly detract from the quality of the beer served.