The process of mashing having been described, the apparatus employed must be considered. A mash tun in its simplest form is a vessel of convenient size and shape, in which the malt and water can be mixed together, and from which the wort can be drained off. Mash tuns aze usually made of wood, but oast-iron tuns are rapidly extending in use. A mash tun should have a capacity of from three to four barrels of malt, at least. Cast-iron mash tuns are constructed in segments bolted together, the connecting flanges being planed and truly fitted, or rust-joints being used. The bottoms of such tuns are usually formed of segments around a central casting, having as many sides as there are segments. It is necessary to case these metallic tuns in order to prevent too rapid radiation of heat ; and the smaller the mash tun, the greater is the necessity for this protection, because the area of exposed surface is in greater proportion to the contents than with tuns of more considerable capacity. To enable the worts to be drained from the goods, mash tuns are made with perforated false bottoms, placed at a short space above the bottoms of the tuns. These false bottoms are made of wood, of cast iron, galvanized sheet iron, or of copper. When wooden false bottoms are used, the holes in them should be burnt, not bored, so that they may not be liable to close up by the swelling of the wood when damp, and they should be well countersunk on the under side. The cast-iron false bottoms are also countersunk on the under side, the countersinks being cast in the plate, whilst the holes are drilled or punched.
The removal of the welts is effected at four or more points independently, so that in the event of the wort drawn from one portion of the tun not being clear, the tap communicating with it can be shut off. Another plan for attaining this end, is by an arrangement of mash-tun bottom, of which Fig. 302 is a section. The peculiarity in this form of mash-tun bottom is that the wort is drawn off from a number of points, at one and the same time, through a series of radiating tubes, H, of various lengths. The pipes H communicate with a central chamber, fitted with a removable top. The space below the false bottom with which the pipes El communicate is divided into compart ments by the strips D, on which the false bottom rests, and the whole apparatus is constructed so that it can be readily removed from the mash tun for cleansing purposes. The pipes F and I serve for the removal of the wort, regulated by the cocks J.
Mash-tun covers vary greatly in construction and efficiency, and in some instances, as in the case of the mash tuns used for porter brewing at the City of London Brewery, they are dispensed with ; this, however, is an objectionable practice, particularly in tho case of large mash tuns. The simplest form of cover is a plain wooden disc, fixed a short distance above the mash tun ; the space between the disc and the tun itself being closed by sacking whilst the mash is being made. Mash-tun covers of this kind are used at Reid's and other breweries. At Mann, Crossman, and Paulin's brewery fiat wooden covers are used, but are suspended so that they can be lowered to the mash tuns.
Another form of wooden mash tun cover is adopted in Allsopp's brewery. In this instance the mash tuns are covered by a permanent wooden roof, carried by a framework extending above the sides of the mash tun, and this frame is fltted with sliding shutters. Another plan is to form the oover of wooden segments of convenient size, applicable to nnash tuns of moderate dimensions. At Hoare's brewery there is a very large cast-iron mash tun, capable of mashing 190 qrs., fitted with a dome-shaped cast-iron cover ; the central portion is fixed whilst the curved rim is formed of a number of flaps hinged to the centre. At Truman's brewery, the covers aro formed of sheet copper, stiffened by brass ribs of T section. Each cover is in two parts, the central part carried by suspension rods at a fixed height above the tun, and the outer part, hung from chains which pass over pulleys, and provided with balance weights, so that this part of the cover can be raised and lowered. The junction between the two parts of each cover is formed with a projecting flange, which bears upon a ring of indiarubber carried by a corresponding flange on the c,entral part of the cover.
Before the introduction of machinery, the malt and liquor were mixed in the mash tun with oars, or wooden stirring-rods, and this method is still adopted in very small breweries. Where larger mash tuns are employed, such method of mashing would not only be too laborious, but would produce most unsatisfactory results. The appliances most desirable for mashing are those best effecting the thorough mixing of the hull and flour of the crushed malt with the liquor, and leaving the goods in a porous condition, so as to be readily penetrated by any further amount of liquor. One of the earliest mashing machines, still in use in many old breweries, consists of a radial frame, whioli travels round in the mash tun. This frame has two horizontal shafts, one above and slightly in advance of the other. Each shaft carries a number of chain wheels, and over these work chains fitted with transverse teeth or rakes. As the shafts revolve, the teeth on the chains are drawn up through the goods, all parts of the latter being successively acted on as the frame carrying the shafts travels round the tun. At Barclay's, all the mash tuns but one are fitted with chain rakes of this kind, and they are also in use at Reid's and other London breweries. At Barclay's, the chains are now made of malleable cast iron. At Reid's, where there are four mash tuns, each capable of mashing 160 qrs., the mashing machine in each tun is double, or instead of the frame carrying the chain wheel shafts being merely a radius of the tun, it extends across the whole diameter. By this arrangement the goods are turned over twice during each revolution made by the frame, and the mixing is thus effected more quickly. In slow gear, the frame makes a complete revolution in fifteen minutes, whilst in quick gear it completes the circuit in ten minutes, the speed being equivalent to one revolution in five minutes with a single machine. In Reid's machines, the rake chains are of wrought iron throughout.