SECTION X.
An enquiry into the Volume of Malt, in order to reduce the Grist to liquid Measure.
Thegallon, by which malt is measured, though less, is nearly of the same capacity with that, which is used for beer or water. The quarter of malt, contains 64 gallons of this measure, and the barrel, within the bills of mortality, according to the gauges used by the excise, contains 36 gallons, but without the bills, 34; though the first quantity is the measure for sale throughout the kingdom. Hence it would appear, that proportioning the grain to the barrel of water would be no difficult undertaking. This however is so far from being the case, that, after having made use of several calculations to help us to the true proportions, we shall find, they want the corroborating proofs of actual experience, to be entirely depended upon.
The ultimate parts of water are so very small, as to make this, as well as all other liquids, appear to the eye one continued uniform body, without any interstices. This cannot be said of malt laying together either whole or ground; there are numbers of vacancies between the corns, when whole, and between the particles when ground, but for our present purpose the volume occupiedby any quantity of malt is properly no more, than the space which would be occupied by every individual corn, either whole or cut asunder, were they as closely joined together as water.
To determine, with precision, the quantity of cold water to be added to that, which is brought to the boiling point, (an act by the brewers calledcooling in) it is necessary to know, what proportion a quarter of malt bears to the measure of a barrel of water. Several operations will be found requisite to come to this knowledge; viz. to take several gauges of different brewings, more especially in the first part of the process; to be well acquainted with the degree of dryness of the malt used, the heat of the first extract, and the quantity of liquor the mash tun holds upon every inch; to find out what degrees of expansion are produced by the different degrees of heat in the first mash, how much less water the mash tun holds upon an inch when hot, than it does when cold, what quantity of water is lost by evaporation, and in what proportion at the several terms of the process. In order to put this in practice, the gauges of the following brewings were taken.
5 quarters of malt dried to 125 degrees.
The heat of the first extract was 136 degrees, to which adding two degrees, for what is lost by the tap spending, the true heat of the mash is 138 degrees.
The first extract, before it is blended with hops, may be estimated to be nearly as strong as a first wort of common small beer. This, when under a strong ebullition, raised the thermometer to 216 degrees, and seven barrels of such a wort, when boiling, occupied an equal space with nine barrels of cold water, at the mean temperature of 60 degrees. Now, if the degrees of expansion follow the proportion of those of heat, the following table, constructed upon this supposition, will shew how many barrels of cold water would be necessary to occupy the same space with seven barrels of wort of different heats.
The quantity of water evaporated in a brewing, when not in immediate contact with fire, is more considerable than it is generally apprehended to be; after repeated trials, I have found that what was lost in this manner amounted nearly to one fifth.
Now since the heat of the first tap was 138 degrees, and my mash tun holds 20,25 gallons upon an inch, the following proportion may be deduced from the preceding table.
and this is the true quantity contained in one inch, at a heat of 138 degrees.
The quantity of water used for the first mash, was 12B. 2F. 3G. or 428 gallons, of which one fifth is supposed to be steamed away, when the first liquor is gone through the whole process of the extraction: but as the gauges of the malt and water together are taken before the tap is set, in the beginning of the process, the whole evaporation ought not to be deduced, and one sixth seems to be a sufficient allowance on this account. We may therefore suppose 357 gallons to be in the mash tun at the time of gauging, which number being dividedby 17,71, will shew how many inches are taken up by the water at that heat.
17,71)357,0000(20,153542———28001771———102908855———1435
or 1,10 inch for one quarter. This number being multiplied by 17,71, the quantity of gallons contained upon one inch at this heat, will give 19,48 gallons for the volume of one quarter of this malt. There now remains nothing but to bring a barrel of water of 34 gallons, under like circumstances, as to expansion and evaporation, with these 19,48 gallons, with this difference only, that as the proportion required is, at the time the water and malt first come in contact, and not after the mashhas been worked, a less allowance for steaming will be sufficient, and may well be fixed at one seventh.
The barrel of water reduced; and as 19,48 gallons, under the same circumstances, were found equal to one quarter of malt, the following division will shew the proportion, between them.
Thus, in malt dried to 125 degrees, the quantity of 1,70 quarters is required to make a volume equal to 34 gallons, or a barrel of water, according to the excisegauging without the bills of mortality; and the quantity of 1,81 quarters is required to make a volume equal to 36 gallons, or a barrel of water, according to the excise gauging within the bills of mortality.
The more the malt has been dried, the larger the interstices are between its parts; the quantity of water it admits will consequently be greater than what is absorbed by such as is less dry. More of this last malt will be necessary to make a volume, equal to that of the barrel of water; and every different degree of dryness must cause a variety in this respect. It will therefore be proper to repeat the operation with a high-dried grist.
Gauges of a brewing of eight quarters of malt dried to 140 degrees.
The heat of the first extract was 142 degrees. Now, by the table of expansions (page 256).
of the water for the first mash, which must be divided by the real quantity of water contained upon an inch in the mash tun.
Excise gauge within the bills of mortality.
Having found the volume of malt at two distant terms of dryness, we might divide the intermediate degrees in the same manner as we have done before, could the certainty of these calculations be entirely depended upon; but as some allowances have been made without immediate proof, how near soever truth the result thereof may from experiments appear, it may be proper to point out what is wanting to make our suppositions satisfactory.
Some part of the calculation depends on the quantity evaporated; this, in the same space of time, may be more or less, as the fire under the water is brisk or slow, or as the weight of the atmosphere differs. The gauges are taken at the time the malt and water are in contact, and more or less water may be imbibed in proportion, both of the dryness and age of the malt; water as a fluid, malt as a porous solid body, must differ in their expansion, but in what proportion is to me unknown; effervescence may be another cause of want of exactness; the different cut the malt has had in the mill, its being or not being truly prepared, and lastly the difference as to time, of the mashing or standing of the grist, prevent our relying wholly upon the calculation. It is, however, not improbable that some of these incidents correct one another. Since 1,70 quarter of malt dried to 125 degrees are equal to one barrel of water, and 1,86 quarter of malt dried to 140 have the same volume, the difference being but 16 parts out of 100, the whole of theerror cannot be very great, and one quarter six bushels of malt may, at a medium, be estimated of the same volume with one barrel of water. But, as experience is the surest guide, I have, from a very great number of different brewings, collected the following proportions, and repeatedly found them to be true. I have added, in the table, the weight malt ought to have, at every degree of dryness.
A TABLEshewing the quantity of malt of every degree of dryness, equal to the volume of one barrel of water, and of the mean weight of one quarter in proportion to its dryness.
With a table thus constructed, it is very easy to reduce every grist to its proper volume of water. Suppose those of the brewings we have already mentioned; that of the small beer consists of 6 quarters of malt dried to 130 degrees, the proportion of which in the table is as 1,75 to 1.
These six quarters of malt occupy therefore an equal volume with 3,42 barrels of water. A brown beer grist of 11 quarters dried to 130 degrees; the proportion of this in the table is as 1,74 to 1.
The volume of these 11 quarters of malt is therefore the same with that of 6,32 barrels of water, and the whole being brought to one denomination, we are enabled to find the heat of the first mash; but the effervescence occasioned by the union of the malt and water must prevent this calculation being strictly true, the consideration of which shall take place hereafter.
The circumstances are different in the other mashes: the waters used for these, meet a grist already saturated, and the volume is increased beyond the quantity found for dry malt. The quantity to be allowed for this increase cannot be determined by our former calculations, and new trials are to be made, in order to fix upon the true proportion.
Gauging is undoubtedly the most certain method of proceeding in these researches; but even this becomes less sure, on account of the expansion, evaporation, effervescence, and other incidents already mentioned.—Our errors however cannot be very considerable, when we deduce our conclusions from numerous and sufficiently varied experiments.
The volume of the grist of pale malt was found, after the parting of the first extract, to be 15,41 inches, though the space occupied by the malt, when dry, was only 5,51 inches: and the volume of the brown grist, at the same period, was 22,36 inches, though the dry malt filled only a space of 8,21 inches. The proportion in both these cases, and in all those which I have tried, answers nearly to one third, so that the volume of the grist, in the second and all subsequent mashes, may be estimated at three times the bulk of the malt when dry, and this is sufficiently accurate for the operations of brewing, in which, for conveniency sake, the application of whole numbers should be effected.
As it is found, by the gauges, that the goods, after the several taps are spent, remain sensibly of the same volume, or at least very little diminished; may we not conclude, the parts absorbed by the water, in which the virtue of the grain and the strength of the beer consist,are contained in an amazing small compass? It is indeed true that hot waters and repeated mashes do swell somewhat the hulls and skins of the malt, but no allowance made for this increase will be sufficient, to remove the cause of our surprise.