Copper steam-pipes 4* sq. ft. .. 67* sq. ft.
Iron .. .. 8 111 Copper with double bottom .. .. 5 .. 82 Cast-iron boiler with double bottom 121 .. 203 Graham is of opinion that unboiled wort, after fermentation, no matter how vigorous the yeast may have grown, never produces sound ales. Worts therefore must be boiled, and the action prolonged, so that the albuminous substances may be broken down in complexity, their activity destroyed, and at the same time colouring matters produced as in malting. In the bailing process, if there should havo been, by chance, any insoluble starch carried over with the wort, it will be converted into soluble starch, but not into dextrine, for soluble starch is not converted into dextrine by the action of boiling. If any insoluble starch is run into tho copper, that starch will be found throughout the subsequent stages. Dextrine in the boiling process is not converted into sugar, although some brewers hold that opinion.
According to the present theory of brewing, boiling may be considered a necessity. Some theorists assert that it is not required, but no practical progress has been made in evidence of good results arising from omission of this part of the brewing process. By boiling, two results accrue, the elimination of a large quantity of albumen from the beer, which is comp/eted after about twenty minutes from the commencement of boiling, and the absorption by the beer of the bitter principle of the hop. But for neither of these results is ebullition necessary, as both may be attained by exposure of the wort to certain high temperatures. With low-dried malts, heat below the boiling point of water will precipitate the albumen of the malt, and a temperature either higher or lower will abstract the better principle of the hop, with, however, slight differences of flavour, resulting from different temperatures. Boiling is practically necessary as a means of evaporation. A copper can easily be made to evaporate 15 per cent. of the water from the beer while the albumen and hop are under treatment, allowing of an equivalent of water being used in the mash tun to extract the malt. Coagulation of the albumen by boiling niay be seen, when a sample of the wort is taken in a glass ; where the malt is low-dried and unsafe, the flakes are large, but when the malt is new and has been well dried the flakes are small. The precipitation is less from the second and third boilings of the mesh tun, than from the first; but notwithstanding this fact, it is the practice to boil the lighter mashes longer, for what purpose there does not appear sufficient reason to show, except that the first portion of the mash cannot be boiled long unless it is a very light brew, while the after portion may be boiled for evaporation as long as the brewer may desire. Boiling is continued for about two hours for the general class of beer. For export beer,
where a great quantity of hop has to be boiled down in a single copper, three hours are sometimes allowed. Heavy beer will require only one to one and a half hour, as the. greater density of the wort is the cause of considerable increase of temperature in the copper. If heavy beers are boiled too long, the pale wort becomes brown, and a. flavour similar to that of porter is given to the beer. Coagulation, and the discolouring of strong worts, occur in comparatively shallow depths, say about 4 ft. in SOMe coppers, so that coppers should be made wider for strong beers than for light beers. The boiling of heavy beers should always be followed by the boiling of light beer, in order to work out the mash-tun products, and utilize the half-extracted bitter of the hop, as well as to recover the strong wort absorbed by the hop in the boiling of the heavy beers. The method of working with repeated boilings and returning the contents of the copper is highly economical, and is generally pursued in the porter trade, where three boilings and returns of hop are common. Double boilings of hop are, however, supposed to be tbe safe limit in beer brewing, and many large brewers will not exceed one boiling with the bop, but disperse the quantity boiled over the malt, amongst tbe boilings of the mash extracts from which the worts bave been taken. In this case, the hop is sent to be pressed to obtain the final amount of extract. It is tb,e opinion of some brewers, who have had large practice, that reboiling of the hop affords great economy in brewing, and is perfectly safe when exposure to air is prevented. Most of those who have failed in trials of reboiling have worked with bigh final temperatures, technically termed bigh tail heats, which have given unsound products in the mash tun, and these, acting on the hop in the copper, extract from it an astringent principle imparting a bad flavour to the beer.