Chapter 6

The aptitude of new hay, malt, and other vegetable matters, to spontaneous combustion, when impacted together by incumbent pressure, and a certain degree of moisture, should be recollected; and that this tendency is not destroyed by excluding the admission of external air, but by quickly cooling and dividing the impacted hay.

The great quantity of oxygen, or vital air, both in the water of dilution, and in the fermentable matter, with which the fluid is more or less saturated, should be also recollected, which is about eighty-five parts in the former, and sixty-four parts of one hundred in the latter.

Though, in an unelastic or fixed state, it is one of the properties of combustion to disengage and render it elastic, great part of which, during the low combustion which it supports, and in which heat is visible or perceptible, and light in an invisible state developed, three parts of this oxygen, with about one third of its weight of carbon, is converted into an elastic state, under the form of fixed air, that separates from the decomposing mass; a circumstance attending also on the combustion of coal and other combustible substances during their decomposition by that process, which supported in them by the external air of the atmosphere, where heat and light are both visible from the intensity and velocity of the combustion; and wholly invisible in the former, not from exclusion of external air, but from the length of time elapsed in low combustion; the one being performed instantaneously, and the other taking several days from its decomposition. Although fixed air is known to extinguish a lighted candle, and destroy animal life, that is, to be equally unfit for the combustion of inflammable bodies, or the support of animal respiration, it is also known to be as successfully employed as atmospheric air, or even dephlogisticated air, to melt glass, &c., when applied to the clear flame of a wax candle, by passing a current of it through a blow-pipe, to direct that flame on the glass to be melted.[4]

[4] Count Rumford on the Economy of Fuel.

This will not be so much to be wondered at, when we consider that the proportion of vital air in fixed air is as twenty-seven to nine, and in atmospheric air, the proportion of azotic gas or phlogisticated air, to vital air, is as seventy-three to twenty-seven; therefore, the former contains three fourths of vital air, and the latter little better than one fourth; but the fixed air is in a combined, and the phlogisticated air in an uncombined state. Among the processes made use of by nature for the decomposition of vegetable and animal substances, fermentation, or low combustion, is a principle one. Air, in a fixed or unelastic state, may be as necessary here as air in an elastic state is known to be in the active combustion of inflammable bodies. Chemists and philosophers are no strangers to two sorts of combustion, one in external air, and the other in close vessels.

But this is not the combustion alluded to in fermentation, where all the requisites for complete decomposition is to be found independent of contact with the atmosphere; here one part is oxygenated at the expense of the other, and the other disoxygenated in favour of it.

Nor does the solution, or decomposition of metals by acids, the combustion of inflammable and vital air for the production of water, stand in need of external heat or fire, any more than the low combustion in which fermentation consists for the production of spirit, beer, or wine, than that generated by the self-operation of its own temperature; similar to this is the self-animating principle or power with which nature has endowed the animal body of generating its own heat by respiration.

In fermentation, the caloric, or matter of heat, which is plentifully disengaged by the condensation of oxygen, is prevented from breaking out into flame with the condensing hydrogen, from the presence of affinities in the fermenting mass, ready to absorb and fix them into vinous spirit, ale, beer, &c., with the other component element, carbon; by which they are too instantaneously taken up and fixed, to amount to more than bare ebullition, and pass at once from an incipient state of elasticity, to a fixed and non-elastic one, while the redundant heat, which would otherwise appear, is taken up and carried off by the abundant formation of carbonic acid gas, which requires so great a quantity of caloric to render it permanently elastic, as not only keeps this sort of combustion under ignition, but much below the degree of heat at which the accumulating vinous spirit could be raised to the evaporable or distilling point, though capable, as already observed, of detaching a considerable portion of it with the volatile gas, and of the water of solution, or the water of composition recently formed from the present attractions in its most volatile and incipient state of formation; both which we have seen ascend with the fixed air extricated, partly in a combined, and partly in an uncombined state.

One part of hydrogen is sufficient to saturate and fix above five of carbon, and they require nearly sixteen parts of oxygen to complete their formation into alcohol, while the water of dilution undergoes a proportionate decomposition and recomposition, to assist the resolutions and combinations, and support the admirable equilibrium preserved by nature.

At the same time that the extreme levity of the hydrogen gas accounts for the great quantity of heat which it holds in combination, and the high temperature requisite to effect its decomposition, and that such is its capacity for heat, that though combined with oxygen and water, it still possesses the property of absorbing a great deal more. It is this property that renders aqueous vapour lighter than atmospheric air in which it ascends; yet we have just now demonstrated the resolution and combination of hydrogen gas, and oxygen gas, both extricated from the fermentable matter and the water of dilution, and their formation into spirit, &c., at a temperature not many degrees above that of the incumbent atmosphere, and no higher than that excited by respiration in the animal system.

In which we have shown the vegetable oxyde, (saccharine matter,) when reduced by the admixture of water, to form the worts or wash, to be a carbonated hydrogenous fluid, containing the elements of wine, beer, ale, spirit, &c., and the mode of producing them under circumstances conducive to their formation; these are motion, heat, pressure, and mutual attraction, called into existence by a species of low combustion, or fermentation, somewhat similar to respiration. In which the materials, the products, and the liberation of caloric are ultimately the same, whether the operation is attended by visible fire from the velocity of action, or weak incalescence from the slow progression of its motion; in which the component elements are continually assuming a gasseous form, and as constantly losing it by the force of mutual attraction for each other. No sooner is the equilibrium broken, in one instance, by their gasseous appearance, than it is restored by their condensation, and the heat liberated by the latter taken up by the former, by which the equilibrium is preserved; in this consists the increase of temperature above that of the surrounding atmosphere, accompanied by the discharge of fixed air; to fix, and advantageously apply which, shall be the next consideration; and, by an accurate imitation of the modification employed by nature, to render the fermenting fluid so much the stronger by such fixation. To accomplish which, we must advert to what has been delivered in the preceding pages, particularly to the proportions in which the equilibrium preserved by nature consists, and exactly to her manner of combining them in sugar, malt, and other saccharine matter, her mode of breaking this equilibrium, or decomposing them by fermentation, and recombining them into wine, beer, &c., and by the same process restoring the equilibrium.

It cannot be doubted, but that, in the investigation of the acetous process of fermentation with the attenuation we do the vinous, they will mutually reflect light on each other; in which it will come out that wine, beer, ale, vinegar, spirit, &c., are not the only commercial preparation to which the doctrine of fermentation, or low combustion, may be advantageously applied, but also to others, that are perhaps equally important and productive.

The cleansing being at the meridian, or greatest temperature of the heat of the fermenting fluid, and the object of that cleansing being to reduce the heat, and thereby allay the violence of the fermentation, by which an immediate decomposition takes place, the lighter impurities buoyed up to the top of the fluid flows off with the yest, while the heavier dregs descend to the bottom, and the fermentation gradually declines as the cleansing draws to a conclusion, and the fermenting fluid forms a turbid heterogeneous mass, very perceptibly approaching towards a transparent homogeneous fluid in its progress to a drinkable state.

In laying out a brewery, the air should have free access to the coolers on all sides, under and over; cleansing vessels should be similarly situated, and, if avoidable, the coolers should not lay immediately over them, to raise their temperature, which should not be many degrees above that of the atmosphere, at temperate, which is fifty-two degrees; but the descent from the cleansing heat (seventy-five to eighty-five) should be progressive, that is, not sudden. A sudden chill would precipitate the grosser, and diffuse the lighter dregs throughout the fermenting fluid, which should be thrown off from the surface in cleansing; this would retard the fining, and empoverish the beer or ale; while the mode recommended will be found to promote transparency, and give strength and body, that is, fullness and spirituosity. In general, the cleansing commences too soon for the strength and quality of the goods, particularly for porter, since the introduction of a greater proportion of pale malt than formerly used; a more perfect fermentation is now requisite to keep up the genuine distinction in that flavour of porter from ordinary beers and ales, which, since the change of _lengths_, has much declined, though the only characteristic quality that gives it merit over other malt liquors--an object that deserves consideration in this great commercial branch of trade, and source of national wealth, where the loss of distinction will be the loss of trade. The rough, astringent, thirst-creating smack is the produce of the brown malt, and a well conducted fermentation. The porter now brewed can no more bear the sudden chill of a cooling atmosphere in the barrel cleansing, without too immediate a condensation and separation of its parts, than it is able to sustain the quick changes of a warm atmosphere, without an immediate tendency to acidity. As things now are, either extreme can only be avoided by a more attentive advertence to the mode of _cleansing_, so as to prevent a predominant tendency to either by adopting the means proposed, or such other, on the same principles, as are equally likely to preserve the quality, increase the strength, promote transparency, and avoid acidity. I know it may be urged by the most able brewers, that a high and rapid fermentation in the cleansing is a principal cause of that flavour for which porter is distinguished; that this kind of fermentation leads to a more perfect attenuation; and some of them may, with great truth, add, a perfect attenuation is the genuine mode of early bringing beer forward. This I most readily grant; it is the doctrine I wish to inculcate. The greater gravity of keeping beers, preserves them in a _mild state_, while their spirituosity prevents acidity. The flavour of the colouring matter now in use, nor the change it induces, is not, by any means, adapted to preserve the genuine flavour of porter, or compensate for that made in the change of malt; a change I by no means condemn, with respect to the malt; but however advantageous to the length, we must not altogether give up flavour, while we may equally as well, and indeed much better, preserve both by a due admixture of each sort of malt, and with suitable additions and proper correctives in the process or preparation of porter, both salubrious; as by the subsequent mixture of stale and mild beer, before sending out, or, afterwards, by drawing them from different casks into the same pot, when on draught, to suit the palate of each respective customer.

I hope it is by this time understood, that my views are to raise the _Process of Brewing_ above the vulgar error that tyrant custom has entailed on it, and by the free exercise of the brewer's abilities, both in a scientific and tradesman-like manner, so as advantageously to preserve flavour and quality, with almost any proportions of every sort of malt he may occasionally be obliged to use.

The world is continually exclaiming that _experience_ is better than _theory_. This is very true; for example, he who has had a very long experience, may, in general, perform operations with tolerable exactness; but this he undeviatingly does by certain stated means, without any deeper intelligence of the process. I would, with Mr. _Chaptal_, compare such a man to a blind person who is acquainted with the road, and can pass along it with ease, and perhaps even with the confidence and assurance of a man who sees perfectly well, but is at the same time incapable of avoiding accidental obstacles, of shortening his way, or taking the most direct course, and alike incapable of laying down any rules which he can communicate to others. This is the state of the artist of mere experience, however long the duration of his practice may have been, as the simple performer of operations.

Brewing, fermenting, distilling, &c., are branches of commercial chemistry, that generally challenge the attention and secure the protection of those governments that constitute them sources of revenue and trade. Chemistry is as much the basis of the arts and manufactures, as mathematics is the fundamental principle of mechanics. In the process of brewing porter, ale, threepenny, &c., to be subsequently treated of, the practical minutia of fermentation and attenuation shall be circumstantially laid down in each, so as to account for, and distinguish the variety of flavour, &c., assignable to each _cause effected_ by the different modes of treatment.

_Hops, the best method of cultivating and raising them._

A rich, deep soil, rather inclining to moisture, is, on the whole, the best adapted for the cultivation of hops; but it is observable that any soil (stiff clay only excepted) will suit the growing of hops when properly prepared; and in many parts of Great Britain they use the bog-land, which is fit for little else. The ground on which hops are to be planted should be made rich with that kind of manure best suited to the soil, and rendered fine and mellow by being ploughed deep, and harrowed several times. The hills should be at the distance of six or eight feet apart from each other, according to the richness of the ground. On lands that are rich, the vines will run the most; the hills must therefore be the further apart.