It then will be left alone (often overnight) until it has reached pitching temperatures, what may take up to the best part of a day. Contamination should not be an issue since near-boiling wort is a very effective sanitiser. Once the wort has cooled to a temperature that is friendly to yeast, the yeast is "pitched" into the wort and allowed to ferment. It is at this point that 'wort" becomes "beer." Primary fermentation in homebrewing takes place in large glass or plastic carboys or food-grade plastic buckets, nearly always sealed. When sealed, the fermenter is stoppered with a fermentation lock which allows the carbon dioxide gas produced to vent, while preventing other gasses and particles from entering. Recent innovations in nanotechnology have enabled a fermentation lock called the Sterilock to also prevent bacteria, wild yeasts and other potential harmful fungi reaching the fermenter although in some beer styles known as Sour Beer, bacteria or wild yeasts are desirable to obtain the sour characteristics. During this time, temperatures should be kept at optimum temperature for the particular yeast strain being used. For ale this temperature is usually ;  for lager it is usually much colder, around . A vigorous fermentation then takes place, usually starting within twelve hours and continuing over the next few days. During this stage, the fermentable sugars (maltose, glucose, and sucrose) are consumed by the yeast, while ethanol and carbon dioxide are produced as byproducts by the yeast. A layer of sediment, the lees or "trub", appears at the bottom of the fermenter, composed of heavy fats, proteins and inactive yeast. Often, the brew is moved to a second fermenting vessel after primary fermentation called a secondary fermenter. This secondary fermentation process is often utilized by more advanced home brewers to enhance flavor. While not required, it is generally practiced by home brewers who wish to age or clarify their beer by removing it from the sediment left behind by primary fermentation. In addition to using two different fermenting containers, some home brewers may choose to only use one container in which primary and secondary fermentation take place. This container is usually referred to as a uni-tank. Uni-tanks are usually conical in shape, and can either be made from plastic or stainless steel. A popular plastic conical for homebrewing is FastFerment, while a popular stainless steel conical fermenter for homebrewers is The Blichmann Fermenator. Upon conclusion of fermentation, the beer is carbonated before it is consumed.