The flavour of newly-distilled whisky is crude and unpleasant. This is particularly the case with pot-still whisky, which contains more of the secondary constituents than the patent. still product. By storage in wooden casks certain changes are brought about in the character and amount of the secondary constituents, with the result that the flavour is improved. This process is "maturing"; it is effected more readily in the patent. still whisky than in that from pot-stills, which is often stored for many years in wood. Casks which have previously held sherry are frequently used for the purpose, and new casks sometimes receive a preliminary treatment with a sweet wine before being employed for the maturing of whisky. Much the greater quantity of the spirit, however, is matured in plain wood. The chemical changes which occur during storage will be dealt with later (p. 452).