Page:A Practical Treatise on Brewing (4th ed.).djvu/117

Rh prove, that when worts are perfectly sound in all the stages of the process, their fermentation will at all times go on regularly and uniformly, if properly managed, and with sound yeast. The only difficulty, therefore, is, to know when any such unsoundness has actually taken place. A slight knowledge of chemistry will then not only materially assist us in tracing the evil to its cause, but also enable us, in after brewings, to prevent its occurrence, should it even proceed from atmospheric influence. As this evil, however, will sometimes arise, notwithstanding every precaution employed to prevent it, chemistry must be resorted to for enabling us to counteract its baneful effects.

If the brewer have a sensitive smell and taste, they will at all times enable him to judge of the soundness or unsoundness of his worts. But when these cannot be depended upon, litmus paper will be found a very useful substitute. All worts, even when running from the mash-tun, contain a portion of acid, which more or less, according to circumstances, will change the colour of the litmus paper. What we denominate sound worts, will give the paper a kind of dirty brownish red. When we find that the tinge of the paper is a brighter red, there must be additional acid, or perhaps a different acid, produced in some part of the process.