Single Malt: length of continous time maturing in small oak casks. To be legally entitled to be a Scotch whisky this time must not be less than three years. Blend: All the constituents of the blend must be more than three years old. The age of the blend is the age of the youngest constituent.   A term used in distilleries in reference to vessels : Wash Back - a large cylindrical vessel of wood or stainless steel in which fermentation takes place. Under Back - A small vessel used to regulate the rate of drainage from the mash tun.   A record book in which details of every fermentation are entered, allowing comparisons to be made over a period of time.   A constituent of spirit, other than ethanol or water. Over 500 congeners have been identified in whiskies. Some of those which are contributors towards flavour are present in only parts per billion quantities.   The means by which advantage is taken of the different volatilities of individual substances to produce a liquid containing more alcohol than is present in the fermented mash, to eliminate solid and involitile matter, and to give a balance of congeners.   A small but generous Scottish measure of Scotch whisky.   A protein or group of proteins, produced within a living cell, which is capable of promoting a specific biochemical reaction.   Any process where a micro-organism breaks down a complex molecule into simpler ones. In the production of spirit this refers to the action of yeast on sugars in the absence of oxygen to produce ethanol and carbon dioxide   An instument used to measure the densities of liquids, by comparing the density of the sample with that of water.   A cereal grain which has been germinated for a short time. Growth is stopped by kilning. For the production of whisky, malt is made exclusively from barley.The purpose of malting is to develop enzymes.   The Process by which the fermentable material in the malt is extracted by hot water and converted by enzymes into simple fermentable sugars.   Freshly distilled spirit is filled into casks to be stored for some years. This is a complex process at the core of which are, the extraction into the spirit of components of the cask timbers, the interaction of the spirit congeners with these extracted conponents and the inner surface of the cask, and the diffusion out of the cask of some of the more volatile constituents.