A flawless wine is clear, this can best be determined especially with a white wine by holding the glass against a light source. With dark red wine this is of course difficult. Cloudiness in the form of clouds, haze or streaks is referred to in wine evaluations with the adjective blind and often indicates a more or less pronounced wine defect. Mostly this is caused by improper winemaking methods or lack of hygiene. The various reasons can be of a physical-chemical nature(proteins, tannins, crystals, metals) or biological nature(bacteria, yeasts) or are caused by substances foreign to the wine such as dust, filter material, cork dust and similar.
The Staubiger wine type defined by Austrian wine law is a cloudy wine marketed without completed clarification. Possible wine faults and defects that manifest themselves through cloudiness include brown fracture, protein cloudiness, acetic acid sting, yeast cloudiness (bacterial cloudiness), cheese, lime clay, lactic acid sting, acidity drop, slime stone, black fracture and white fracture. The cloudy substances contained in the young wine during ageing can be removed from the wine by fining and/or filtration.
Calcium turbidity caused by tartaric acid is not considered a wine defect. Also the residues, mainly in red wine, which are referred to as deposits, do not constitute a wine defect. Suspended matter produced by polymerization during bottle aging is removed by carafing after opening the bottle