MEETING HELD AT THE BALMORAL HOTEL, Edinburgh, On Tuesday, January 30th, 1906.
Mr. Robert Jeffrey, in the Chair.
The following paper was read and discussed.
A Study on Extracts.— Part I (extraction from the mash tun)
By W. Stanley Smith, Ph.D., etc.
I will not conceal from you the fact that the choice of a subject upon which to address you has occasioned me some considerable measure of concern. It appeared to me as an English brewer, and one whose experience of brewhouse affairs in your beautiful and historic capital is of a limited order, that there existed the possibility of my wares being unsuited to Scottish craft; but in deciding upon the topic of “extracts,” I trust I have selected a subject that may prove of interest and utility to my fellow craftsmen on either side of the Tweed. It has always seemed to me that the power of speech is scarcely to be exercised in private without wholesome fear; in public it becomes a trust which should only be used on those rare occasions when one has “something to say.” I must at once confess, however, that to many of you my thoughts and experiences may not contain much that is of a novel character. I have virtually no new truths to propound, no very glaring error of the past to demolish. Indeed, most probably our theme exercised the ingenuity of the ale-wives of Babylon, in those far-off days when the facts and figures of commerce were recorded on tablets of clay. I have come here to learn, rather than to teach, for old as is the theme, it is not yet exhausted; and my excuse for being here at all is the discussion which usually follows these papers. I am selfish enough to hope that our subsequent proceedings will partake rather of a sifting of your views, than a criticism of mine, and I trust our discussion may take the form of debate, in preference to that of mere question and answer.
It was not until the introduction of instruments capable of affording an instant and fairly accurate measure of the “weight” of malt extracts, that any systematic plan of operations designed to effect uniformity of results became possible. The early history of the mash tun is enveloped in as dense a cloud of empiricism as is that of most other arts and crafts; and the very term “misterie,” so often heard in connection with the brewing of ale, affords us sufficient evidence of the jealousy with which the details of procedure were guarded. Even so late as the year 1793, a Scottish brewer’s instructions for the proper production of Edinboro’ ale contained this profoundly mystical note, to wit, “I throw a little dry malt, which is left on purpose, on the top of the mash, with a handful of salt to keep the witches away from it, and then cover it up.” Let it not, however, for one moment be supposed that no wisdom lay inherent in the practice of our forefathers. In many instances their customs survive to this day; and were it not for the fortuitous aid lent us by the inventor, and the spread of technical science, it is doubtful whether the art of brewing would have strayed so far from the paths associated with more or less barbaric ages. I have but to mention one or two striking illustrations to point this moral. In the course of our observations it will be necessary to call attention to the growing custom of screening off all malt below a certain size, and grinding these smaller corns in a separate milL This plan is recorded by Frederick Accum, nearly a century ago, as a common custom among the more important brewers of his day. Again, you will be aware of the popularity of “hop-economisor” appliances, as used in connection with our fermenting vessels, but it may not be such common knowledge that the idea is, also, at least 100 years old, and may be unearthed by the curious in old Mr. Baverstock’s “Treatises on Brewing.” Says he, “It has been asserted by those who have made the experiment, that a far less proportion of hops would serve as a preservative, or to communicate flavour, if it was the practice more frequently to introduce a part of the quantity allowed into the guylotun.
Such is the extensive power of fermentation.” These instances, alone, will serve to remind us that in practical observation the past generations of brewers were by no means unproductive. In fact, the more closely one studies the works of the best 17th, 18th, and early 19th century writers, the more is one impressed with the idea that they possessed that sort of practical, familiar, finger-end knowledge which a watch-maker has of a watch. The position is much the same to-day; but we have at our finger’s-end that rich harvest of facts garnered by labourers in many a fertile field of modern science.
It is, as I have said, not without anxious thought that I choose the study of extracts, as controlled by modern brewing procedure, for our consideration on this occasion. The standard of excellence we brewers must set before ourselves is, of necessity, a high one—perhaps, too exalted to admit of ever consistent attainment. But it is a standard which has been fostered by the formation and success of the various sections of the Institute of Brewing, and it is an ideal in which, I am sure, we all share. In the words of the late Professor Huxley (who, by the bye, received from Edinburgh the first academic distinction conferred upon him in Britain), we must strive to import into our business “the highest scientific habit of mind,” and, whenever feasible, bend our efforts to promote the unity of that couple, alas! too often divorced, science and practice. It may be asked, How can this best be accomplished? I can, at least, indicate the road. The superfluities of enthusiastic, but youthful, science, the fine epithets, the sweeping statements, must be pruned, sifted and weighed to the needs of modern industry. Truth need not of necessity be bald; but the fact remains that the real utility of science lies more in accuracy of statement than in luxuriance of diction. Have something to say, and say it, was the great Duke of Wellington’s theory of style. We should apply this theory by word and in deed; we should strive to follow the fundamental principles, as they appeal to us in our own time. These begin with observational science, or facts collected; they proceed to classificatory science, or facts arranged; they end with inductive science, or facts reasoned upon and laws deduced.
The chief essential of good extract lies, of course, in the malt. “Malt,” says Lintner, “is the soul of beer.” It is more; it is soul and body. In fact, as Carlyle might have put it, it is beer, minus time. But I do not intend to occupy these fleeting moments with so obvious a truism. It is rather my intention to develop the lines which lead to the most thorough extraction of the available material from malts of all sorts, sizes, and descriptions. The physical, as distinct from chemical, conditions which afford the best results with one class of malt material, will surely in due ratio prove best for all, and it appears to me that a careful consideration of the factors which surround and govern our mash-tuns renders it quite within the reach of practical technology to frame these conditions in the form of laws or rules. They must be based, as we have indicated, upon observational science, facts collected; the inductions from these facts will, in due course, form those guiding principles which may fittingly regulate the daily routine of the brewhouse. The first point we will subject to our analysis is that of grinding—the reduction of malt to a physical state in which the inner content of the grain presents a suitable number of points of contact to the solvent. I have an ineradicable habit of finding out what other brewers, who lived and worked in earlier days, have to say on such-like fundamental details in brewing empirics, and research through many records of both the distant and the near past has not failed to reveal, as usual, a full measure of practical and well-founded observation, touching on this very subject. It will therefore be of profit if we rapidly scan two or three of the more weighty opinions uttered in those bygone years.
The very words “malt,” “grist,” and “mill,” which we are accustomed so glibly to use, bear an original interpretation pregnant with meaning for the industry to which they apply. In its naked simplicity malt is but the idiomatic Saxon contraction of mailed, in other words bruised. The Romans, who contrived to infuse so much of their own conquering spirit into the equable insular temperament of our mead-drinking forefathers, endowed us with a broad-faced hammer or pestle, dubbed malleus; whence it requires no exercise of extreme subtlety to derive our modern mallet and malt. Yet the extraction is curious, and, when considered from the brewers’ point of view, remarkably interesting. Grist, again, is but that which thou grindest, and the mill, by Saxon’s termed molin, and by their descendants miln, was a mechanical invention for crushing to flour or meal. From Dom Boc days till the yesteryear our mill has simply served as a crushing machine, and its limits were strictly defined in terms of mash-tun drainage. The old writers, whose words I am now to quote, were not concerned with extract per se; for, in sooth, their range of industrial vision did not extend beyond the, so-called, buoyant tun of “goods” That these limits were taught by common sense and expediency none can deny; but we, I hope, shall more particularly discern their narrow confines. The senior person I intend to quote is an old-world follow, whose name I know not, but whose personality is vivid in The London and Country Brewer, published nearly 200 years ago, and indited by one who describes himself as “a Person formerly connected in a Public Brewhouse in London. Chapter VI of this precious work is headed “Of Grinding Malts” Says the author, “as trifling as this article in brewing may seem at first, it very worthily deserves the notice of all concerned therein; for on this depends much the good of our drink; because, if it is ground too small, the flour of the malt will be the easier and more freely mixed with the water, and then will cause the wort to run thick; and therefore the malt must be only just broke in the mill, to make it emit its spirit gradually, and incorporate its flour with the water in such a manner that first a stout beer, then an ale, and afterwards a small beer may be had at one and the same brewing, and the wort run off fine and clear to the last.” So much for the unknown—we will merely mark his words as to clarity, and note his preference for coarse grist. The point of view held by Combrune, our next author, is strikingly similar. His book was published in 1762, with “permission of the Worshipfull Company of Brewers,” He tells us malt must be ground “in order to facilitate the action of the water on the grain, which otherwise would be obstructed by the outer skins.” And listen to the sequel: “Every corn,” says Combrune, “should be cut for this purpose, but not reduced to a flour or meal, for, in this last state, the grist would not be easily penetrable. It is therefore sufficient that every corn be divided into two or three parts, nor can there be any necessity for varying this in one sort of drink more than in another. The intention of grinding is the same in every brewing, and the transparency of the liquor, mentioned by some people on this occasion, depends by no means on the cut of the corn.” Here, again, it is clear that physical conditions, closely connected with “transparency of the liquor,” or drainage, chiefly occupy, and certainly limit, the learned authors’ thoughts. It seems strange, perhaps, for us to disentomb the erudition of these erstwhile lights of the brewhouse, but, believe me, the phenomenon of “reversion” is not solely manifest in matters of enzymic action or the breeding of hounds. Thought, like the elements, has its Periodic Law. Hence, we pass on in no mood for apology, to consult old Richardson. He was the man who did more to popularise the methods of saccharometry than any other of his contemporary brewmasters, with the possible exception of Baverstock. And, moreover, in old Richardson’s utterance we discern the germ of a modern notion, namely, that of the finely-ground grist. He is discussing the oddities of varying extract yielded by malts hailing from North Lincolnshire, Berwick-on-Tweed, and the Yorkshire Wolds, and on page 238 of his book, The Philosophical Principles of the Science of Brewing, of which I am the happy possessor, these following words may be found, as written in explanation of extracts varying some 7*5 per cent., in malts obtained from the aforementioned barleys. “It might result,” says Richardson, “from the difference in grinding the same malt rounder at one time than another; for the intention of malting being the production of that saccharum, and other dissoluble parts which constitute the value of malt, it follows, of course, that in proportion as that process approaches to perfection, the increase of those valuable parts will be effected; and as the crushing of every kernel in pieces is indispensable to the setting at liberty of fermentable matter, it is obvious that if the operation of grinding be so carelessly performed that a certain number pass through the stones unbroked, the products must be less in proportion which these bear to the whole. Hence a continued attention is necessary to the preliminary particulars, as a foundation for those advantages which are to result from posterior considerations.” Here, indeed, is weighty truth, and no modern babbler on beer ever more nearly hit the mark.
Two further citations will serve our purpose. Mr. William Black, writing in 1835, manages in his cogent remarks on grinding to entirely forecast our own sentiments. “There are,” he says, “various opinions as to the fineness or coarseness of the grist, or grinding, some contending that if the pickle be at all broken by the rollers, the malt will not only give as good an extract, but that their taps will spend finer; a point to which many attach great importance. I am, however, of opinion that finer grinding will produce rather better extracts; and if the first liquor be properly taken, and allowed to remain long enough on the goods, there will be very little difference in the fineness of the worts; at all events, they will be quite as bright in the jack, or hop back, and perhaps also a little stronger than those from coarser grist.” So much for Mr. William Black, of 1835. I reserve my last citation from the comparative ancients as, perhaps, the best. It is a germ of wisdom due to the author of The Scottish Ale-brewer a certain W. H. Roberts, whose book has the distinction of having been published by the famous firm of A. and G. Black, of Edinburgh. “In England,” says Mr. Roberts, “there has long existed a difference of opinion, whether grinding or crushing is the more beneficial to the brewer; that is to say, whether he will obtain a better and a finer extract from malt ground with mill-stones, or malt bruised by rollers. My opinion, (continues Mr. Roberts) is decidedly in favour of the latter system, providing the malt is good, and that the wort is for ale; and it appears to me a matter of surprise that, amongst so many intelligent and scientific men (this was written at the dawn of modern science, in 1847) there should exist such difference of opinion. Certainly, if the malt is bad, the rollers will not crush it sufficiently; for, in this case the barley has not been well malted, and consequently the pickles are tough, and at the same time flinty, instead of being short and mealy.” Then follows some words in which we discern a gleam of technical intelligence now fully dawned. “Upon a cursory view,” says Mr. Roberts, “the ancient way of grinding by the mill-stones may appear the best; as we are apt to consider the more finely the malt is ground, the more readily will the liquor penetrate, and consequently we shall obtain a better extract.” The chief objection to his own argument noted by this thoroughly practical brewer, is the danger of the “goods” setting, and thus defeating the very object for which a fine grist system is devised.
An ingenious French writer observes that those who depend on the merits of their ancestors may be said to search in the root of the tree for those fruits which the branches ought to produce. Be this as it may, it will be obvious, from the words I have quoted, that even a century ago the trend of educated opinion lay mainly in favour of fine grinding as a means of increasing the extract. Nowadays, as we go further, and roundly assert that the whole secret of high extract is centered in this fact The limits imposed upon the set of malt rolls were, and until recently always have been, dictated by questions of mash-tun drainage. This is the reason why, when many of us signed our articles of apprenticeship, we were taught that malt should not be ground, but merely crushed or cracked. This alone excuses the eccentricity of fluted rolls, once so popular. The traditions fostered by centuries of difficulty over drainage became a fixed and settled article of faith, and articles of faith in the brewing world suffer hard and lingering decease. There is, however, one solid consolation for all the many millions of good extract that have been lost on this tradition, and that is—the pigs and cows have, no doubt, hugely benefited there from. Yes, I repeat, the prime secret of high extract is fine grinding.
A malt mill, constructed on modern principles, is a veritable triumph of engineering ingenuity. The screens, brushes, dust fans, magnets, distributing rolls, and every other essential, form together as perfect a machine as ever the wit of man devised. There is, indeed, nothing wanting to secure our aim—a clean wholesome grist, free from dust, nails, stones, straw, string, or any other of the odd things yielded of malt. The only question which suggests itself to me, in connection with our supposed ideal modern mill, touches upon the rolls themselves. As a general rule these are constructed of mild steel, which can be placed on a lathe and turned up, when the ravages of time, iron nails, and other adamantine entities have scored the pristine smoothness of their surface. Most professional brewery engineers will have nothing but mild steel for malt mill rollers. I am, however, much inclined to advocate the virtues of chilled cast-iron for this purpose, especially where the lessons of fine grinding are to be put to practical test. There are, I am fully aware, several objections to this extremely hard type of metal. It is said that a grave danger of smashing up the mill exists, when such unyielding surfaces are opposed by nails and stones—species of matter in the wrong place, which somehow or other occasionally manage to elude the screens, magnets, and every other contrivance designed to bar their ingress to the mill rolls. This danger is real, but when one of tho pair of rolls is fitted on a yielding bed, it will by reason of its very hardness be driven apart from its neighbour, and allow the foreign body to pass through uncrushed.
In many instances, where chilled cast-iron rolls are in use, it will be noticed that any stray nails or stones, which find their way on to the rolls, past the distributor, will dance like peas, and seldom be drawn in to the rapidly revolving mill. Mild steel, on the other hand, is invariably badly scored by any roving foreign body, and, its surface being less smooth, the very friction set up renders the pea-dance movements of extremely rare occurrence. Now every mark or indentation on the surface of mill rolls is a score against the attainment of high extracts. It is impossible to effect uniformity of grist and fine grinding with channelled rolls; it is equally impossible to set rolls with uneven surfaces close enough together for our purpose. Whilst one portion of the surface may be at just the right distance from the companion roll, another part may be too widely separated therefrom, and to adjust this means, perhaps, friction and rapid heating at certain areas of the surfaces. When using chilled and polished cast-iron rolls, the adjustment of distances is a far more easy matter, and the element of friction is reduced to an almost negligible quantity. I shall probably be asked : What is the proper distance apart at which rolls should be set? I propose to anticipate the query by giving the details of my actual procedure. I have found that the rolls may be set at from 1/20—1/70 inch apart, and that the closer the rolls are set, the higher are the extracts secured. In Table I I have embodied a series of practical tests, which are intended to illustrate the relations existing between grinding and extract. It should be mentioned that each line contains the average figures of about 30 separate analytical observations.
In most breweries it is customary to grind each class of malt separately with the result that the foreman is continually adjusting the index roll, to suit, as he deems it, the varied bulk of different types of malt. Acting on the tradition that more cracking of the kernel is all that is necessary, or, indeed, judicious, this method is not without justification. The long lean grains, which ere they reach our shores are baked in southern climes, obviously demand a closer set system of rolls than the plump and mellow product of favoured Scottish or English acres, assuming, of course, that the mere cracking theory is right But, as I have said, I do not think it is right, in fact, I have emphatically stated my view, which is founded on extended experiment, and which leads me to an entirely contrary conclusion. The question is really how one can, in the most expeditious and advantageous manner, prepare this finely ground grist. Here again I will give you my own experience as to the best means to employ. The various qualities and types of malt it is proposed to incorporate into the grist should be well mixed up together before grinding, and then passed through a screen which eliminates all corns below a certain size. These small corns may then be separately ground, and this is best done by passing them through a smaller mill kept specially for this purpose. I am fully conscious that this suggestion may remind you of the story of Newton and his favourite cat and kitten, but nevertheless the plan has certain marked advantages, which will readily occur to the practical brewer. It saves undue interference with the index of the main mill, and it ensures, beyond the possibility of doubt, that each and every corn is crushed. The idea is not even novel: it was mooted by Accum a century ago, and it is, for aught I know, followed out in many a modern brew-house. It solves any lingering difficulties in the way of obtaining fine grist, and I have found the best results follow on its adoption. But I anticipate a possible objection which may be raised against this system of mixing up the various malts before grinding. It is quite a common custom amongst brewers to start grinding with some of the long-husked foreign malt, so that this grain may be the first to pass through the mashing machine, and thus ensure a good drainage bed on the false-bottom plates. As a matter of fact, however, the great bulk of the malt which is the first to be ground is about the last to be mashed. It is, on the other hand, quite obvious that the method of mixing will ensure a considerable measure of uniformity in the grist, and that when it is coupled with carefully devised means of incorporating substitute material, it will, I am confident, yield results characterised by a satisfactory and uniform percentage of extract.
In connection with the subject of preparing our grist for the mill, 1 may be expected to say something with regard to preliminary kiln treatment of the malt prior to crushing. The system of placing malt on the kiln, and heating it up to about 140° F. 24 hours before grinding, has much to recommend it. From the strict extract point of view, and that is what we are more immediately concerned with at present, I cannot say that I have been able to detect results either favourable or otherwise in connection with this preliminary kiln treatment, but I am certain that the ultimate flavour of the beers has been usually improved thereby, and a point is thus gained which may well rank in importance with extract yield, and which well repays the time, labour, and expense involved in kiln work. After being removed from the source of heat and stored in sacks, or otherwise, for 24 hours, the average temperature of the malt as it passes through the mill will be near 70o F., and at this degree it will grind perfectly, and yield a fine, crisp, sweet-smelling, flour-like grist. I need hardly say that modifications of striking heat of the mashing liquor will follow on this system of kiln treatment, and that in my opinion such modifications, tending as they do to diminish striking temperature, cannot be anything but beneficial. The more nearly the striking temperature of the mashing liquor approximates the ultimate initial heat we desire in our mash-tun, the more nearly do we approach ideal conditions for the yield of extract. But, as against this, weighty questions of expediency will operate when we attempt to present to the liquor a grist which has already been warmed up to the desired temperature of saccharification.
I make no attempt to develop this point on the present occasion, but it will be obvious that a gradual and measured permeation of liquor throughout the mass of grain contents will be bettor fostered in the absence of evident shocks, such as might accrue by the use of striking liquor at temperatures very considerably higher than those we aim at for carrying out the process of the decomposition of starch.
There is just one other little detail which it may be worthwhile to mention at this juncture. Malt, as we know, generally contains a considerable mass of foreign matter, such as nails, stones, and other substances which do not require definite enumeration. And although most, if not actually all, of these undesirable bodies arc removed by the special contrivances provided therefore in a modern malt mill, yet when the grain is conveyed to the malt hopper on a jigger, or by means of an Archimedian screw, the provision of a few small pockets on the road, say about 3 inches deep, will greatly aid us in freeing our grain from undesirable constituents. In these pockets will he found a large collection of the stones, nails, heavy dust, and other matters which, by reason of their gravity, have naturally sought a lowly place.
The next operation which comes under notice is that of mashing. When one is dealing with grist which has passed through rolls set so close as 1/50—1/70 of an inch, it will be readily understood that this operation requires to be conducted with the greatest care and skill. A coarse grist will stand considerable friction and be none the worse for vigorous “knocking about”; a fine grist, such as I advocate, requires gentle, thoughtful handling in its progress towards our mashtuns. Until the day arrives when all these difficult questions and details which appertain to mash-tun drainage are solved by the universal use of the filter press, the cares and worries associated with a “set” mash will constantly be ours—unless, of course, we devote the same intelligent thought to the details of mashing as we have done, and consistently do, to many of the other important processes involved in the industrial manufacture of beer. “With very fine grist the practical procedure revolves around this principal point, namely, very careful regulation of the speed at which the machine travels. The proper rate to drive an outside mixer, such as Steele’s excellent contrivance, is just that rate which ensures efficient admixture of grist and liquor. This, and no more. The slower the rate, consistent with proper mashing, the better it is for meeting after conditions that will prevail in the tun. Fast driving tends to develop a set and sodden tun of goods, and to encourage a state of affairs which may, in the end, defy the utmost skill and persuasion on the brewer’s part. Set mashes and high extracts do not live in the same street. I think it is the general experience that Steele’s machine yields good and uniform results, and when driven at the right speed gives an admixture of malt and liquor as perfect as needs be, On the other hand, adherents are not wanting to the method involved in the use of a so-called automatic mixer, and whilst this type of machine does not, perhaps, admix the grist and liquor so intimately as a Steele machine, yet it has often been observed how buoyant is the mash for which an automatic mixer has been employed. This simple fact teaches us to exercise care where a Steele is installed, for by duly regulating speed and other conditions a perfect mixture may be obtained, combined with the utmost buoyancy of goods. Quite recently a new type of masher has been devised, the drawings of which have been kindly lent to me by Messrs. Braithwaite, of Leeds, and which I have laid upon the table. The principal feature of the new masher is that it affords greater control over the mash as compared with the old method of hot liquor supply. The grist-slide is in two parts, and opens from right to loft, giving a central fall of grist to the masher mouth. The slide is actuated by worm gear from either side of the masher. The hot liquor feed is in the form of a gunmetal breeches pipe, spanning both sides of the masher mouth, the water being sprayed on the falling grist through slots at both sides, running full length of the mouth. The rake spindle is of Muntz metal. Immediately under the hopper is an Archimedean screw, followed by blades which are adjustable, and which may be arranged to retard or accelerate (or even combine these actions) the flow of the mash, until it be discharged in a thoroughly mixed state, yielding, it is claimed, an increased extract. The rake shaft with worm and blades, is made a fairly close fit in the barrel of the masher, compelling the mash to pass through the mixer. Mash-tun rakes, again, must be sparingly and cautiously used, as high speed or excessive application will invariably result in a disturbed and sodden mash. The value of rakes in the mash-tun from an extract point of view is supreme, and it is only their misuse, in other words, too frequent use, that must be carefully avoided. Many an ugly mash has been set aright by one slow turn of the rakes; indeed, in cases where they are needed at all they are quite indispensable, and in cases where it is possible they are not really needed, they do no harm, so that, from every standpoint, experience extols the virtues of, and proclaims the necessity for, a well-regulated system of mash-tun rakes.
The whole question of mashing machines must, at this juncture, be regarded more or less from the subjective point of view. There are changes of standpoint taking place which may eventually alter our technical procedure in most material fashion. I have but to mention Professor Windisch’s latest dictum, in order to indicate the trend of modem thought on this extremely important matter. The learned Professor contends that the external mashing machine is already obsolete, and that an up-to-date brewer must necessarily discard this same piece of apparatus. I am not aware of the particular axe this eminent expert is, at present, engaged in grinding, but I honestly think, so far as British brewers are concerned, his advice is somewhat premature. The objects to be attained by a mashing machine are stated by Windisch to be as follows:—To occasion the preliminary admixture of grist and liquor, in such manner as to avoid lumps in the mash-tun. Secondly, we are to avoid the escape of malt dust; and this is, assuredly, a laudable desire when we set ourselves to deal with a finely ground grist. But Dr. Windisch argues that the introduction of centrifugal rousers or propellers, in place of the ordinary mashing rakes, has made the formation of lumps in the mash impossible, whilst an extension of the tubular grist chute, so that it dips below the surface of the liquor in the tun, prevents the dust from rising. All this is well and good, and is possibly fit pabulum for the Continental master of many mash-tuns. It is also possible that, under modern conditions, the external mashing machine wastes both time and money. As Windisch says, the grist requires from 15—45 minutes to pass through the machine, and under these conditions it is conceivable that the first portions receive a longer brewing than the last. Again, it is possible that the mashing machine limits the degree of thickness And temperature which can comfortably be employed in making up the mash; but, surely, we have the practical and potential limits of all these factors in sufficient command, under present conditions.
I now propose to devote a few minutes to considering the conditions which regulate the dimensions of our mash-tuns. This important topic has already been sifted, many years ago, by the late Mr. E. R. Southby, and that in a manner which leaves little or nothing of a novel nature to advance. In fact, I think that the dimensions he has sketched out in his book on “Practical Brewing” may, with advantage, be followed to this day; but, at the same time, the value of his figures is confirmed, to my idea, by a train of reasoning which would probably not have occurred to any practical brewer before the tradition of coarse grist had been definitely shifted to the limbo of things forgotten. Nowadays, we aim at fine grinding in order to secure all the available extract, and the dimensions of the mash-tun must be so regulated that the mash remains buoyant, and capable of absorbing in a given time a given weight of liquor. The connection between depth of goods, drainage, and extract is of a very intimate order, and these three closely allied factors may with great advantage occupy our attention, especially as regards their relation to another factor which, in judicious hands, can control and regulate those inequalities of ratio in the three first-named factors, and which, in industrial procedure, must inevitably be frequently in evidence, I refer, of course, to the sparge. In order to secure the highest extract with the least amount of trouble, or of mash-tun disturbance, I have found that the ideal depth of goods, in a 16-foot tun, and at the finish of mashing with two barrels per quarter, is about 65 inches wet dip. During the first quarter of the time it is proposed to occupy in making up the coppers, I find it is best to allow the goods to sink about 4 inches, and to carefully regulate this lessening of wet dip throughout the process so as to conform to the conditions which are actually taking place in the mash-tun. From the first moment of setting taps, a gradual decrease in the volume of malt contents is set afoot, and the lowering of the wet dip of the goods does not necessarily mean we have less liquor in the tun, at any given time, but rather that we have a constantly diminishing amount of malt material. I think the object we should have in view is the maintenance of a fairly constant ratio of liquor to malt material, so that the relative proportions of each are kept as uniform as possible throughout the process of extraction. I do not wish this suggestion to be taken in any arbitrary sense, but rather that it should embody the larger suggestion that a definite and regular rate should be cultivated in the fall of the goods. It will be observed that the adoption of some such plan of operations will, at least, assist us to draw off the extract without causing any violent shock to the goods. The effect of disturbance during the hours of sparging and running-off will generally be apparent in the movement of particles of heavy gravity, which may, sooner or later, result in complete stoppage of the regular, mechanical drainage so essential for securing the available extract of malt. A steady running of the taps, especially during the earlier stages, is of paramount importance for many reasons, not the least being the effect this careful procedure has in checking the gravitation of amorphous and nodular bodies, such as acrospires and hard ends, towards the lower layers of the goods. And the advantage of sparging on a definite plan, such as I have adumbrated, is not only confined to maintenance of the ratio of liquor to malt material, but it is also evident in its tendency to maintain the status quo of those heavy, partially insoluble, bodies throughout the entire bulk of the mash. The further these bodies are from the plates, and the more they are diffused, the less detrimentally will they act upon the drainage of the tun. Violent and erratic sparging, conducted without system, will often, on the other hand, occasion such a rapid flow of liquor through the goods, that the amorphous substances will speedily form a layer which we know too well is practically impervious to the liquor.
The depth of goods at the conclusion of mashing, which I have stated to be the most practically perfect for purposes of thorough extraction, is to a large extent controlled by this very factor we have just mentioned. In adopting as our rule of procedure the system of fine grinding, we must adapt every possible detail to the assistance of drainage in the mash-tun, and the maintenance of buoyancy of the goods. Now, if you will cast your eyes on this diagram, you will at once see how a comparatively shallow mash will assist in counter balancing the effects of an impervious layer of amorphous material. It is presumed that each tun contains a like quantity of malt. In the deep tun, of narrow diameter, a given quantity of amorphous material will naturally form a much deeper and denser layer, impervious to the liquor. The shallower mash-tun, as against this, offers a far greater area for impervious material to spread itself over, with the result that drainage through this much thinner and far less dense layer is scarcely impeded at all. I need hardly press the point any further—it is very obvious how largely the question of extract must be controlled by mechanical factors of this nature. There is only one other detail in connection with drainage to which I will direct attention. When the taps stop by reason of defective drainage, one often hears the brewer complain that his false-bottom plates are choked. This is seldom, or never, the case. As a matter of fact, free drainage can generally be restored by one turn of the rakes; and if the impervious layer had settled on the plates, it is obvious that no turning of the rakes, which do not touch the false-bottom, would effect a cure. No!, the amorphous material does not reach so far down as the plates; it stops some inches above, and that for reasons we can only surmise. It may be due to the pressure exerted by a layer of hot air between the false-bottom and the actual bottom of the mash-tun. That such an atmospheric cushion is normal to the tun, during the period of drawing off, seems probable from several phenomena commonly observable. For instance, if taps be shut off and the rakes started, it seems as if air bubbles were rising up through the goods, and a considerable amount of foam is formed. A gauge-glass fixed up the side of the tun, starting from the space between the actual and false-bottoms, also supports the view that a cushion of air is normal to that space. Soon after mashing the level of liquor in the gauge-glass will approximate to the height of the goods, but this level in the glass decreases far more rapidly than the height of the mash as the wort is drawn off, until very soon there exists no settled proportion between the two, and the relative rate at which the taps are run appears to control the column of liquor in the gauge-glass. The general conclusion I have arrived at, as touching upon this question of drainage, is that, in nine cases out of ten, when worts do not run freely from the tops, the resistance is in the tun itself, and not in the plates. If half the slots or holes were blocked up, it would not much affect the rate of flow, as I think is evident when one considers the relative area for drainage from the plates, and area for water to be distributed over the mash from the sparge arms. I heard the other day of an American device which tends to illustrate this point, inasmuch as excellent results are said to follow on its adoption. It simply consists of a mash-tun fitted with one central slotted plate, fitted in a converging bottom.
There is just one other advantage to be gained by adopting a definite system of dropping the goods gradually, and in such a manner ns to maintain a more or less fixed ratio between liquor and malt material and that is the decided minimising of the dangers of flooding, when, towards the middle of the drawing-off process, the rakes are used, and the operation generally called “mashing-up” is undertaken. I take it that the top layer of a mash, at half time, consists largely of lighter material, which has gravitated to the surface; under this is, probably, a zone in which liquor is in excess, and below this we might expect to find an area in which the better part of what extract remains is occluded. There can be little doubt that by maintaining, as far as possible, the homogeneity, or consistency, of the goods, by a judicious system of sparging quantities, the tendency to form layers of material of lighter gravity will be considerably minimised, so that when the rakes are used there is far less danger of undue disturbance, and consequent causation of flooding.
The resistance to passage of liquor through a mash-tun is, of course, largely controlled by depth of goods. In the old days, when grinding was made dependent upon the sparger capacities, the question of points of contact for solution was subsidiary to the all-important necessity of maintaining buoyancy. Hence, with a coarse grist, offering relatively less resistance, the depth of goods assumed a less prominent position, with regard to the question of extract, than we must concede to this point in these days of finer grists. Indeed, if we are to err at all, it may well be in the direction of shallower mashes. The difficulties of drainage which are encountered when one is dealing with deep mashes of finely ground malt are sometimes considerable, and I have found the shallower mash to work better, whilst yielding at the same time an equal extract if rather more sparge liquor be used. Let me illustrate this point. In a certain tun 58 quarters of malt were mashed with the object of producing an 18 lb. beer. The depth of goods after mashing worked out at 58 wet inches and some 6*8 barrels of sparge liquor per quarter, or 6*8 x 58 = 394*4: barrels in all, were necessary for making up the coppers. The goods invariably run well and free, and the extract is also invariably satisfactory. On other occasions, however, 74 quarters of malt are mashed in this tun, to produce a beer of 22 lb. gravity, and the depth after mashing amounts to 70 wet inches. With this mash there is seldom such free running, as is the case with that first mentioned, and the finely ground malt tends rather to resist the liquor in its passage through these deeper goods. In all 444 barrels of liquor are sparged, i.e., 6 barrels per quarter, as against 6*8 barrels over the shallower mash, but extracts come out much the same, so that the extra 0*8 barrel of liquor has done its work, and overcome the tendency for comparatively shallow mashes to permit the too rapid flow of liquor, with consequent loss of extract. In other words the increased washing counterbalances any defects inherent in more or less shallow mashes. You will note that the ideal depth of goods I have mentioned approximates in wet inches to the mean of the two gauges quoted above,
i.e. 58 + 70 = 128 ÷ 2 = 64 inches.
The whole question of quantity of sparge liquor demands careful attention and consideration. It is a factor which has an important bearing on the proper extraction of available malt extract. In all malt beers the quantity of liquor we may use is practically restricted within a narrow compass. Ignoring unnecessary finesse in our argument, it may be said that the liquor available for sparging under all malt conditions of brewing is simply that particular quantity from which a wort is produced which in the copper is about the same gravity as the beer we wish to brew. And it is here that a frequently unconsidered benefit arising from the use of saccharum is evident, because its use will permit of greater latitude in the quantity of sparge liquor. Again, the large contrasts in beer gravity as witnessed in the production of strong ales and ordinary “running” beers, come within our province from the extract standpoint. In producing strong ales, the taste for which, by the by, seems to be rapidly on the wane, we make use of relatively more malt with fewer barrels of sparge liquor per quarter, as against the weaker brew with much less malt and a considerably greater measure of sparge liquor per quarter. In such cases the time clement looms large and brewers will not need to be reminded how extract from heavy mashes may be thoroughly exhausted by adjusting the rate of sparge and the rate of taps—the inflow and outflow—in an intelligent and suitable manner.
I have mentioned the time factor. Here, indeed, we have a fine point for discussion, a point quite apart from the consideration involved in depth of goods or fineness of grinding. I have never heard a sound opinion expressed upon the good or bad influence of a short or long time in running off worts; but my own view extends at least to experience of the benefits which always accrue from that extra half-hour’s rest which follows on one turn of the rakes at half-time. To pursue the time factor too far leads, obviously, to a reductio ad absurdum. There are incidental elements to be reckoned therein, besides the actual extraction of malt content; and there are influences in different breweries which must affect the duration of time spent in making up coppers, quite apart from the extract question. In many of our smaller brewhouses, for instance, the brewing must be got through and finished in 12 hours, to avoid overtime and to enable the single-handed operative brewer to curtail his working day within reasonable hours. In such cases, if more than three and a-half, to four hours be taken up in running off the worts, the eventual collection of the gyle in fermenting vessels is inconveniently prolonged. Another brewhouse may find it necessary to use the plant a certain number of times during the week in order to produce the required quantity of ale for their trade, and in such cases it may be highly inexpedient to prolong the running of taps. And, yet again, there are establishments where the lengths brewed, and style of coppers used, must exercise a considerable effect upon the time element; where, as an example, they boil in three coppers, or three different lengths. These, we must concede, are all points upon which expediency will largely adjudge, and as the time saved may conceivably be of greater value than a small increment of extract, one would hesitate to pen a set of mice after the manner of those framed by the early Medes and Persians. And yet, as I have said, the whole subject is ripe for discussion at the hands of those rich in that experience which alone teacheth. Here I can only fringe the matter by adding an odd observation or two on the phenomena one notices when mashes are allowed to stand at various periods during the time of running off the worts.
It is well known that if we let our mash stand at the point, say, when the taps show a gravity of 2 lb., after an interval of time, which we will take as half an hour, these taps will show a higher gravity. It is obvious that extraction has accrued, and if the increase of tap gravity be anything considerable, it is equally obvious that we have to encounter defective mash-tun conditions. I do not wish to unduly emphasise any trifling rise of gravity that may occur on the mash standing, as in practical affairs it is unwise to split hairs, but in cases where the increase is notable the matter demands investigation. With shallow mashes, brewed to fashion higher gravity beers, and run off too quickly, the cause is obvious, but with average mashes, for running ales, where the usual time precaution has been observed, we must look to other causative phenomena. I think one of the most common is to be found in the “channelling” of the goods. Liquor, like other physical entities, has a habit of seeking paths of least resistance, and the inevitable result is that in the mash-tun, at least, these paths assume in time the relative proportions of channels, through which liquor will flow without adequate contact with the bulk of the goods. The matter centres on diffusion, and proper diffusion is one of the safeguards to be aimed at in our efforts to obtain the available extract from malt. It is quite reasonable to suppose that if the sparge liquor be rushed through our goods, or if it be not properly distributed on the surface, the time necessary for the formation of homogeneous solutions is lacking, and lighter fluids will more speedily descend. The mass of water, being unequally distributed throughout the mass of grist, must tend to inequalities of tap gravity. Faulty sparge apparatus, and uneven mash surface, may combine to cause unequal distribution of liquor over the surface, the consequence being that pools are formed, which tend to assume large proportions, and the weight of the water thus concentrated forms conical cavities, whence it will flow as down lines of least resistance. That this takes place seems proved by the fact that, at the earlier stages of running off worts, the taps often vary in strength, especially about half-time, when the sparge liquor begins to work through. Here we have an object lesson in what I have called “channelling”, and no doubt the inequalities in tap gravity are further occasioned by the fact that the mash-tun rakes afford surfaces down which liquor can course in a free and easy fashion. But by checking the lower gravity taps diffusion may be encouraged and equalization of gravities can generally be achieved. Of course, by far the most practical and convenient method of equalising gravities, as of encouraging equi-proportional diffusion, is to run the rakes round at half-time very slowly and carefully. The stronger wort from the lower depths of the tun is commingled with weaker stuff from the upper strata, and the homogeneous liquid thus induced can be far more readily washed through the filter-bed of goods than is the case when at every point a different pressure is exerted.
Before I close my remarks I should like to say just a few words on the results obtained by adopting this system of fine grinding. In the first place I found this method quite impossible under the old-fashioned conditions of sparging. The goods flooded and set without exception at every mash. But when I took the question of more perfect sparging apparatus in hand, and alighted upon my friend Mr. Harris’ ingenious devices directed towards this end, most of my initial difficulties ceased to trouble. I have not had time to dwell on the points which to my mind constitute the ideal form of sparging apparatus, but I hope to continue this “study on extracts” in a paper to be read before the Manchester Section of the Institute of Brewing early next May, and to develop this important topic in further detail. Suffice it for me to tell you that in using a grist composed of 43 per cent. English malt, 15 per cent. Californian, 17 per cent, flaked maize, and 25 per cent, inverted cane sugar, I have found the average extract obtained with fine grist and, what I may term scientific sparging, to be 3*3 per cent, higher than under the old conditions of coarse grist and clumsy sparging. In other words, the former average of 88 1b. per quarter now stands at 91 lb. per quarter on total grist.
I have dealt in the main with purely practical details. Indeed, I may perhaps be accused of having laboured the obvious, but I would not have it supposed that my words or attitude suggest a picture of the modern brewer as a sleepy and incurious creature. The possibility is remote in strenuous times like our own, and I am convinced that what some critics may denounce as indifference is an attitude not founded on crass ignorance, but rather on that long experience which has taught us the need for caution. When men are doing their work according to the best of their ability, they are sometimes prone to complain of the slighting words which those more closely associated with pure and exact science feel it incumbent upon themselves to utter. For us, however, the ordinary day’s task, duly considered and conscientiously carried out, will, at all times, suffice to bring its own reward, and I feel convinced that the reward will be all the greater, the bettor we learn to appreciate both the scientific aspects of our industry and the many practical details which become increasingly valuable, and ever deeper in interest the more thoroughly they are studied.
The Chairman said that he had listened to a very interesting paper.
Dr. Smith seemed to have obtained very remarkable results by his system of mashing and sparging, and he had been very much struck with his description of these methods. He was sure many would be able to give their own experiences on mashing, etc., with a view to increase of extract.
Mr. Heslop inquired if the author had ever noticed any difference in the drainage of his mash-tun with different malts.
Dr. Smith replied that there was no difference in the extract, as fine grinding neutralised that.
Mr. Donaldson, referring to the measurements Dr. Smith had given, inquired how the author put his rolls up. A gauge of 1/20 to 1/60 of an inch had been mentioned.
Dr. Smith replied that he used tin plates between the rolls. These plates could be got to any gauge. He kept a set of plates, so that the mill foreman always noted at what gauge the rolls were set. He had embodied that in a table.
Mr. Lorimer said he was sorry there had been so little discussion in regard to this very interesting paper, and with the view of trying to evoke a little more discussion he might mention an experience he had a long time ago which ran contrary to Dr. Smith’s theories. On one occasion the sparge was out of order, many of the holes being chocked up, and it was not distributing the liquor at all well. He was assured by a consulting brewer that there would be a great increase in the extract when the sparge was put into proper order; but to his disappointment there was no difference in the extract after the sparge was set right again. He doubted if the gain would be very much greater as the author imagined. Of course, Dr. Smith spoke from actual experience, whereas he gave the result of a single experiment only.
Mr. Gall asked if the author considered 25 per cent, of maize grits would make a difference in the quality of the beers.
Dr. Smith replied that he believed 17 per cent, would be a very good proportion to use, but he did not think it advisable to use more. He got excellent drainage with that percentage. He would not, however, like to give a decided opinion as to the quantity to be used.
Mr. Baird inquired what difference Dr. Smith had experienced between brewery and laboratory extracts with his system of grinding.
Dr. Smith replied that with very fine grist the extracts were precisely the same. With coarser grist the results were wider apart.