In that known as the Edinburgh mode of mashing, all the water required is sparged on after the first =filth. By this method, as soon as the taps have become fine, sparging is commenced, and tapping and sparging go on simultaneously until the extraction is complete. In working this system, the error is commonly made of putting on the sparging water too hot, even at a tempera ture of 82° to 88° (180° to 190° F.). The first sparge heat should not exceed 77° (170° F.), and if the temperature of the mash exceeds 68° (156' F.), the sparge water may be at only 71° (160° F.). The tun covers should be removed whilst sparging is proceeding ; and water should not lie on the top of the goods whilst sparging, which always occurs if the mash has been too hot, or the sparge water added at too high a temperature. The water remains on the surface of the goods in conse quence of coagulation having commenced, and the temperature of the sparge water should be at once lowered, and the taps closed for a short time. When the temperatures have been properly adjusted, the goads freely rise from the bottom of the mash tun and float, and allow the extracting liquor to readily peroolate. This is an important point, and the goods should be kept up at least 6 inches from the bottom of the tutt until the end of the sparging. As small brews must have the same time to extract as large brews, the runnings must of course be smaller in quantity ; and for this reason the sparge water must be hotter than with large brewings, where the running off is performed so much more quickly. The small quantity of water falling from tho sparger will cool more quickly than the larger quantity falling through the sante space.
After a mash has been maintained with the sparger at the temperature of 68° (156° F.) for about two and a half hours, the heat of the water should he auddenly lowered 12° or 15°, so as to reduce the action of heat iipon the goods to 66° (150° F.) towards the end of the aparging and running. In making strong beer, the necessity for strength will have required the running to have been stopped within two and a half hours, before the reduction of temperature, so that the effect of this reduction will be felt on the aftorwort only, which may be table beer. If it is require,d to pump the tail ends of one mash over for the sparge liquor of another, all that is necessary to ensure success is that the tail goods come off one mash at 63° to 66° (145° to 150° F.), and are re heated by a steam coil, attached to the pump, to the necessary sparge heat of 77° (170° F.), or that producing 68° (156° F.) in the mash.
Tap heats afford no safe guide to the brewer, for the almost obvious reason that these do not truly represent the temperature of the mash.
In the best practice in porter brewing, the temperatures of the mash do not differ much from those given for ale. Saturation should take place at about 1° lower, the temperature for the mash being ultimately the same as for beer, or 68°. The peculiarly dry, sub-acid flavour, common to Irish porters, is the result of too great range of mash heats, by beginning at too low and finishing at too high a temperature, thus twice submitting the mash to the chances of acidity. Porter is best
made from malt two-thirds of which is well-dried pale, and the remainder high amber and black. Roasted malt should be used to the extent of 1 bushel to every 5 or 6 barrels of finished beer. Brown or blown malts are a mere waste of grain, will not keep, and yield little extract. The roasted malt is generally put into the mash tun amongst the other malts, but sometimes it is put into the wort copper and boiled with the hop. An alternative method of great profit to the brewer on the large scale, is to mash the roasted malt by itself in a small tun fitted with a rake and false bottom, and an inner perforated concentric diaphragm through which to drain off the black extract. The washing out is performed with the extract from the large mash tun.
Before proceeding to the description of the apparatus used in mashing, it will be convenient to describe the operation of sparging, as the mechanism employed in .both cases ca. n then be classed, as they are used, together. Sparging is the process of extracting the remaining wort, which adheres to the insoluble draff or grains. The sparging is carried out by means of hot water, and if the wort has been run off at a temperature of about 63° to 66° (145° to 150° F.), the sparging liquid, as has been stated, should not be used above 77° (170° F.). This process goes on in different breweries to different extents, sometimes it is carried to such an extent that the wort obtained is excessively weak, containing only some 4 to 6 lb. a barrel. This is not usedt a once for the production of beer, as a rule ; it is not mixed with the previous wort, but is pnmped up into the copper and there used for the subsequent wort. This return wort, as it is called, is exceedingly liable to undergo decomposition, by which acidity, mainly due to lactic acid, but probably to other acids as well, is produced. In order to prevent the return wort from becoming acid, it is found convenient to keep it at a temperature of at least 88° (190° F.), and from time to time to add a. little bisulphite of lime. Throughout the whole of the period, whether during the night or during the day, until the next time of use, the return wort must be kept at least as high as 88°, for if allowed to fall to 66°, acidification is very liable to set in. The wort resulting contains not only sugas and dextrine, but also an amount of albuminous matter ; this amount depends upon two or three conditions, and chiefly upon the nature of the barley originally employed. For instance, if the barley came from the North of England or Scotland, or if it had been growing on heavy land, it would contain much more albuminous matter, than barley grown on a light warm soil. And brewers occasionally make an error in judging of the strength of the wort, by merely depending on the use of the saccharometer, because the soluble albuminous matter sustains flota tion of the instrument as well as sugar and dextrine. The amount of albuminous matter in the wort also depends on the previous malting process ; lastly, it depends on the nature of the water employed.