386 STUDIES ON FERMENTATIOX. 



mechanical action, similar to that which we notice in fining 

 operations. On the coolers an effect of this kind is produced. 

 The wort in the copper contains insoluble matters which pass on 

 to the coolers. Very bright when boiling, it grows turbid as it 

 cools, and then contains two kinds of insoluble substances : 

 I. Substances insoluble alike in the hot and cold liquid, some 

 of which even, as we have just seen, are formed under the 

 influence of heat and air : all these substances precipitating 

 rapidly to the bottom of the vessels. 2. Very fine particles 

 insoluble in the cold, but soluble in the hot liquid, appearing as 

 tlie wort cools down, and giving it a milky appearance. If the 

 air does not come into play the}^ remain in suspension for an 

 indefinite time, so to say. Wort taken boiling from the copper 

 and cooled down, therefore, forms a considerable deposit at the 

 bottom of the bottles. Now, if we put this wort into bottles 

 without filling them, putting into some only the milky wort 

 from above the deposit, and into others the same wort along with 

 some of the deposit, then raise it to 100° C. (212° F.), and 

 before it has time to cool down shake it up with air a good many 

 times, it will be readily seen that the wort in the bottles con- 

 taining the deposit will brighten more rapidly and satisfactorily 

 than those in the bottles without the deposit. The deposits 

 which are insoluble in the copper have, therefore, an influence 

 on the clarification. We must add, however, that this influence 

 cannot be compared with that of direct oxidation. 



The " turning out " of the wort and its stay upon the coolers 

 to a certain extent exhibit the difierent conditions which take 

 part in its clarification, inasmuch as the wort charged with its 

 insoluble matters is run off* very hot, and with more or less 

 violence against the external air. 



