Red wine is a type of wine made from dark-coloured (black) grape varieties. The actual colour of the wine can range from intense violet, typical of young wines, through to brick red for mature wines and brown for older red wines.
The juice from most black grapes is greenish-white; the red colour comes from anthocyan pigments (also called anthocyanins) present in the skin of the grape; exceptions are the relatively uncommon teinturier varieties, which produce a red colored juice. Much of the red-wine production process therefore involves extraction of colour and flavour components from the grape skin.
Most red wine is aged for some period before bottling, though this can vary from a few days, in the case of Beaujolais Nouveau to 18 months or more in the case of top Bordeaux reds. Ageing can take place in stainless-steel or concrete tanks, or in small or large oak barrels. The latter impart some flavour to the wine as a function of their age and size (small, new barrels give more flavour than large, older barrels).
Red wines sometimes undergo fining, which is designed to clarify the wine and sometimes to correct faults such as excess tannin. Fining agents include egg white and gelatin. Some red wines, particularly those designed for early drinking, are cold stabilized so as to prevent the precipitation of unsightly tartrate crystals in the bottle.
Most wines are filtered at some stage before bottling, though some winemakers use the absence of filtration as a marketing tool. Filtration serves to make wine completely clear and to eliminate any remaining yeast cells and bacteria, which could render the bottled wine microbiologically unstable. Wine is normally filled to glass bottles with cork stoppers, though aluminium screwcap closures and plastic stoppers are becoming increasingly common. Alternative containers such as Bag-in-Box, TetraPak and plastic bottles are also used.