408 



trouble called casse, or causes the colour of the wine to " break." 

 Two cassea are known, the "brown" and the ''blue." Sulphur 

 fumes are used as a preventative or a colour restorer. Used as a 

 preventive, it gives better results. Six grammes of sulphur per 

 100 gallons after aeration and before fermentation, six grammes 

 when first drawing off, and six grammes when racking for the first 

 time, will prove efficacious against this trouble. 



VATTING is the name given to that period during which the 

 must is in contact with the husks. As a rule, short fermentations 

 result in delicate wine, with good keeping qualities ; long fermenta- 

 tions producing harsh wines, heavy in colour, and not so easy to 

 keep. 



Whenever possible the vatting of the grape pulp should be 

 done by gravitation ; time and labour is saved, and the work is 

 done with greater cleanliness. 



The filling of the vat should be done during the day, and 

 not spread over two or three days. 



It is immaterial whether only one or several kinds of grapes 

 are mixed together in the va.t, provided that they be all of one type 

 and are meant for making one class of wine. Each sort is, however, 

 generally fermented apart from the other, and the resulting wine is 

 blended afterwards if required. 



The vats should not be filled to more than four-fifths of their 

 capacity, as much swelling of the mass occurs during fermentation, 

 and if the rise of the liquid occurred during night time loss of wine 

 would result. By keeping the level of .the fermenting must below 

 the edge of the vat, excess of air is to a great extent screened off by 

 a layer of carbonic acid gas ; whilst being about three times as 

 heavy as air, covers the fermenting liquid and prevents oxidation 

 and acetification of the cap or floating husks. 



Questions are often asked : Should the fermentation be con- 

 ducted in open or in closed vessels ? Should the skins or caps be 

 kept immersed or left to float during fermentation ? In both cases, 

 more especially in hot countries, both theory and practice strongly 

 favour open vats and submerged heads. There takes place during 

 fermentation a chemical reaction which results in the splitting up 

 of grape sugar into alcohol and carbonic acid. This reaction, which 

 is set up by living organisms or yeast, is accompanied by much 

 evolutions of heat, and the richer the liquid is in sugar, the warmer 

 the temperature, within limits, which we will consider presently, 

 the greater that evolution of heat becomes. 



Unless some means exist of dissipating that heat generated 

 during fermentation, its accumulation would reach a point which 

 would soon endanger the life of the active agent of fermentation. 

 Fortunately, two natural outlets exist for the dissemination of that 

 generated heat : 1st, radiation from the surface and through the 

 sides of the fermenting vessels ; 2nd, by the free escape of the 

 carbonic acid gas, which rises to the surface in warm bubbles which 

 burst and allow it to escape. 



