Industrially produced flavouring substances in powder or liquid form, extracted from various types of wood. Most liquid extracts are based on pure alcohol. They are added to red wines as an alternative to expensive barrique ageing or to improve colour and taste. Within the EU the use of such substances in liquid form (essences) is prohibited, but in solid or powder form is permitted. In solid form these are wood chips (pieces of oak wood). Such substances are considered to be oenological tannins. See also under Barrel (types of ageing) and agents used in winemaking.