What to look out for

Warning signs browning . . . A bad sign in young wine (probably oxidised), though quite acceptable as the colour associated with ageing, matured red wine - most evident on the rim of the wine against the glass.

bubbles . . . Normal in sparkling wine, and a small amount of tiny bubbles can be acceptable in "sur lie" wines that retain more carbon dioxide from fermentation than most still wines, but otherwise they usually warn of instability (bacterial spoilage).

cloudiness, haziness . . . Could be okay up to a point in certain older wines, or wines that have undergone little to no fining or filtration, or no malolactic fermentation, but a lack of clarity can also point to bacterial spoilage.

pinking . . . When white wines turn light pink after bottling, it's usually indicative of over-reductive winemaking - too deoxygenated. Could also be a sign of oxidation.

slick . . . An oily film on the surface of the wine in a glass is invariably caused when the glass (or the decanter) hasn't been properly rinsed or dried.

ullaged . . . A bigger-than-normal air-space between the cork and the wine in an unopened bottle can result from seepage (leaking cork) or evaporation. Too much ullage can mean the wine in the bottle is oxidised.

NO PROBLEMO:

crystals . . . Shiny tartrate crystals on the cork or inside walls of the bottle (resembling tiny shards of glass) are unsightly but harmless and don't affect the quality or character of a wine. Sometimes they're regarded as a positive, indicating a less processed wine.

sediment . . . Harmless tannins and tartrates that separate out of the wine and settle on the side or bottom of the bottle - usually due to little or no fining or filtration of the wine. Can be ignored, or removed from the wine by the process of decanting.