Page:A Practical Treatise on Brewing (4th ed.).djvu/115

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The process of fermentation has generally been considered by brewers as very mysterious and uncertain, and over which they have no control. This to a certain extent is no doubt true, for the yeasty heads covering the beer in the gyle-tun during fermentation will assume different appearances according to the fluctuations of the weather, and the seasons of the year. In summer we never see the light yeasty heads in the third change, rising to the fine rocky or alpine appearance which they assume in open frosty weather, nor do the yeasty heads in the fifth change become so close or solid. Windy or hazy weather also affects differently the appearance of the heads of the beer during fermentation.—(See Regular Fermentation.) Over these different appearances, therefore, We have no control, and very likely never shall, unless we could also command the weather. But although we cannot at all times attain the same fine appearances during fermentation, by proper management we can always obtain a sound, regular, and healthy fermentation, and which will invariably produce good beer. We shall now proceed to show how this may be accomplished.

All irregular or unhealthy fermentations arise either by the worts becoming tainted from bad