600 MEETING HELD AT THE CRITERION RESTAURANT, PICCADILLY, W., ON MONDAY, OCTOBER 17th, 1910. Mr. Lawrence Brunt in the Chair. The following paper, by Mr. C. S. Meacham, was read by the Hon. Secretary, Dr. L. T. Thorne: Pneumatic Mattings. By C. S. Meacham. There have already been contributed to the Journal of the Institute three papers on this subject, i.e., J. Sleeman, 1891; Dr. Hiepe, 1898; and Briant and Vaux, 1901. The "Honning" drum system has been so well described in both of the last-named papers the principle of the system with drawings by Hiepe, and the method of working by Messrs. Briant and Vaux, that it does not appear necessary for me to go into a detailed description of the system. I shall, therefore, confine my remarks to points arising out of what may perhaps be considered as a severe working test, the result of experience with an installation of 18 30-quarters capacity germinating drums, under severe climatic conditions. Even the short winter at the Cape is not very favourable for floor malting, and the summer temperature is, of course, consider ably higher than the summer temperature of the United Kingdom. Under such conditions a pneumatic system is the only one workable, but both its advantages and disadvantages become more apparent than would be the case in a cool climate. The above-mentioned plant, if worked continually to its fullest possible capacity without a stop for the whole of the year, is capable of making 16,300 quarters, or 90 quarters every t\vo*days. In practice, however, we do not get beyond the rate of about 12,000 quarters per year for the following reasons: (1) As the building is practically full of machinery, and this is working continuously day and night with the exception of very short intervals, it is better to give it a rest and complete overhauling once a year, and this may well occupy a month.
MEACHAM: PNEUMATIC MALTINGS. 601 (2) Owing to the disadvantages of working, and the extra cost for power in very hot weather, it is advisable to atop malting for the one or two hottest months of the year, and this is also the time when some of the hands are busy taking in the new season's barley. (3) By steeping on regular fixed days three times a week, the work is kept regular and systematic, and heavy work on Sundays is avoided. One of the chief characteristics which differentiates a pneumatic from an ordinary floor malting of equal capacity is the small area of the building, owing, of course, to the small ground space taken up by the germinating drums as compared with floors. This point affects the question of barley storage. The pneumatic maltings practically consists of four storeys 1st, the germinating floor; 2nd, the steep floor; 3rd, the barley bins; and 4th, the staging over the barley bins containing the hoisting, conveying, cleaning, and screening plant The steep room is of the same area as the germinating floor, and the barley bin room as much less as the space taken up by the kiln-turning machinery, etc., at the end of the bin room. Where a supply of barley for nearly a year's working has to be stored (particularly in a warm climate), the question of storage is of much greater importance than where, as in ordinary floor makings, sufficient only has to be taken in during the late autumn and winter months for the winter season. This is particularly the case at the Gape, whore the whole of the barley for the year has to be taken into the maltings within the space of the first few months, and these the hottest months of the year, the temperature of some of the barley going into the bins being as high as 75 F. It is here that the small area upon which the maltings stands is a handicap, on account of the restricted space available for the barley bins. There is prac tically no storage space in the steep room, for, besides the six steeping cisterns, the floor space is partly occupied, from one end to the other, on both sides of the steep tanks, by the belt conveyors; there are elevators at both ends of the room, whilst the valve openings from the barley bins are distributed over the entire overhead space. There is, therefore, only room here to temporarily Btow a few hundred quarters in sacks, whilst the steep room, being naturally a damp room, is not suitable for prolonged storage of barley. 2x2
602 MEACHAM: PNEUMATIC MALTINGS. Now, the storage of, say, 10,000 quarters of barley on a floor area of somo 4,500 square feet means the construction of very deep barley bins, and this is assuming the outer walls of the building to be taken as part of the bins, in which case the walls would, of course, need staying and tying together (my own experience, however, has been with a nest of 32 wooden bins of a depth of 25 feet, built inside and free from the walls by a space of 2 feet). Storage is, under these conditions, a somewhat risky matter, and in such a warm climate is very subject to an attack of weevil. The damage resulting under such conditions, in spite of all that can be done, is considerable. I would strongly advise that the barley bins in a pneumatic makings should not be constructed of wood, and there is probably no better way than forming the partitions of reinforced concrete, with the necessary dividing walls to provide for proper grading of barley and for localising any outbreak of weevil that may arise. It has generally been stated that barley, if kiln dried, is not subject to weevil attack. My experience does not endorse this, as weevil have developed strongly in kiln-dried barley only a couple of months after kiln drying. Kiln drying does not kill the egg or larva of moth either, as these also hatch out after barley has been well kiln dried. Before leaving the subject of barley storage, it is as well to point out that when the malting operations are in continuous progress, there is, of course, no opportunity of utilising the malt kilns for barley drying. If the barley is to be dried, a separate drying plant should be installed, and from my own experience I consider it a very desirable adjunct to a pneumatic makings, although my experience does not endorse the opinion that kiln drying prevents weevil. I would, however, recom mend drying on kilns rather than in drums, for reasons that will become apparent when dealing later with malt-curing drums. The only means available for turning over the barleys in these deep bins is that of transferring from one bin to another through the barley conveyors and elevators. As these same conveyors and elevators are in use every alternate day for conveying barley to and from the barley screens for steeping, they are not always available for trans ferring barley. For stock-keeping purposes such transference of barleys has, of course, to bo carefully recorded in "Barley Bin Book." There are several objections to continual transference of barleys from one bin to another. First of all, it is a costly process, for there is
MEACHAM: PNEUMATIC MALTINGS. 603 the extra fuel for additional load on engine, as well as wear and tear of machinery, and if the operation has also to bo carried out at night, it means an extra, man. Secondly, the passing of barley at a high velocity from bin to conveyor, conveyor to elevator, from tho elevator again to conveyor, and finally the force with which it passes down the chute from the conveyor and strikes the bin or the barley below, cannot be beneficial to the germ of tho barley. As an instance of the velocity with which the barley enters the bin as it leaves the conveyor bands, it has been found necessary to line the wooden bins with sheet iron on any part where the stream of barley may como in contact with the sides of the bin, as the wood soon becomes bored out* It is advisable, of course, to avoid this concussion with the sides of the bins, and where possible this is done, but in a large nest of bins it is not possible to prevent it in every case, owing to the angle of the chutes. Canvas bags put on the mouth of the chute to deflect the barley do not last long, and 'need frequent renewal. To sum up the above, I should recommend that more extensive area for barley storage should be pro vided than is afforded by the area of the germinating drum room, so that the barley has not to be stored at so great a depth ; that where such long storage is required as in pneumatic makings, the bins should not be constructed of wood, but of iron or concrete; bins kept as few and large in area as consistent in dealing with different sorts of barley, but with outlet valves fairly close together so as to allow of the removal or transference of barley from any particular part of the store without much trimming. Steeping. The steeping process does not call for much remark beyond noting tho fact that the system of throwing the grain from the top of the cistern by means of compressed air is rather costly in the matter of power and water. The amount of compressed air taken for changing over steeps from one cistern to the other for aeration purposes, and when emptying cistern, makes such a demand upon the air reservoir and compressor that air pressure on the water sprays in the coke tower is for the time partially suspended, and this, in very hot weather, is felt at onco in the rise of the temperature of the air taken into the germinating cylinders. The chief object of making the cisterns to thus empty over the top, instead of by a valve at the bottom, is to aerate the barley during the steeping process, and also to save height in the building, as in this cose the bottoms of the
604 MEAOIIAM: PNEUMATIC MALTINGS. cisterns can be kept down below the level of the top of the germinating drums, whereas if they were in a position to empty each cistern to command any of six drums from the bottom, a considerable height from the top of the drums to the outlet of the cistern would be required. It is a case of pros and cons; the cisterns must, of course, come in between the barley bins and germinating drums, and if the cost and inconvenience of blowing over the steeps for emptying is to be avoided by increasing the altitude of the cisterns, then more head space in the steep room will be necessary, and the higher will be the floors of the barley bins and the whole building, with the further consequence that all barley has to be raised this additional height by barley elevators. I merely point out the matter for information, without making any definite suggestions for its remedy, beyond the obvious one in regard to air pressure that the air reservoir should be of such size as will not allow the pressure to be too quickly affected by the amount used for the cisterns. In a hot climate whero the temperature of steep water is never low, the benefits of aeration during change of grain from one steep to another are, of course, felt to the full. We now come to the prime factor in pneumatic maltings the germi nating.drums and, naturally, if there is any point of interest to discuss, it will centre round these. It has been generally stated, and I think accepted, that the best system of germinating in drums is that in which the air is drawn through the growing grain, thus enabling the operator to control temperature and growth. In the drawings in Hiepo's paper ( /". Fed. Inst. Brew., 1898, p. 237), [which he tells us were supplied by the makers], it is shown by arrows how the air passes inwards and upwards from the lower inlet tubes on the periphery of the drum through the mass of growing grain to the inner tube, and Hiepe says " the air can pass into the first small chamber, then through the growing barley into the middle tube." Briant and Vaux in their paper (1901) also say "provision is made whereby those tubes which are not covered with the grain are closed, so that the air in passing from the exterior to the interior of the drum has to travel through the grain" Hiepe's second drawing also shows the " provision spoken of by Briant and Vaux for shutting off the air from the inlet tubes which are above the level of the growing grain." I am sending with the paper a drawing of the device in question, which is
MEACHAM: PNEUMATIC MALTINGS. 605 a fan-shaped sheet of iron kept in position to close the apertures above the surface of the grain by a pendulum-like weight, the whole being balanced upon a central pivot (Diagram A). The impression derived from the abovo-quoted statements, and which I believe closely agree with the claim put forth for the Uenning drum, is that the air is drawn through the body of the growing grain, and is prevented from entering the drum at a point above the surface of the growing grain, and this, I think, is generally accepted as taking place. It is my object now to show that this is not what actually takes place, or rather that it, at all events, does not take place in the degree suggested by the statements and drawings quoted above. Diagram A shows a section of a drum charged with germinating DlAOBAM A. DlAOBAM B. barley. A is the central perforated tube through which the air is drawn. B, B, are the air inlet tubes, whilst the dotted line shows the level of the germinating barley at the angle it assumes as the drum slowly rotates. Of these air tubes, three marked with a cross are above the level of the grain, and may be imagined to bo closed by the iron screen which is marked C. It will, I think, be readily admitted that, as the air is drawn from the centre tube of the drum by a suction fan, it will be taken in where there is least resistance, and this would, of course, if the air could gain access, be along the entire length of the upper portion of the central tube, where the malt is thinnest.* However much the drum is revolved, the surface of the malt, of From this point I shall, for the sake of simplicity, in every case speak of the growing grain ns " Malt."
606 MEACHAM: PNEUMATIC MALT1NG8. course, retains approximately the position marked by the dotted line. Now, to stop the air from thus gaining an easy access to the tube through this thin layer of malt is, of course, the function of the iron screen (shown in Diagram A), and if this were effective, then the air must go through the mass of the growing grain if the fan were powerful enough to draw it, and wo should have a condition of aeration corresponding to our previously conceived notion of what takes place. If this were actually the case, the air would, to its fullest extent, be capable of keeping down the temperature. If you will look at figuro A, however, jrou will see that the iron screen, instead of completely covering up the mouth of the end of the tubes B, B, leaves a space on the outer edge uncovered (the space showing black); this space is about an inch wide, and as the air drawn through this is only restricted by the thin edge of the iron screen, and not by any length of orifice, the amount of air which can obtain access through this space is very considerable. In whatever position the drum may be, there are always three such tubes exposed. The first thing occurring to one's mind, on finding a drum so constructed, is that it is an accidental defect, but an examination of the whole of the drum reveals the fact that it is carefully arranged so by the makers. In seeking an explanation for this, the one which appears the most plausible is that the makers in their first plants found that if the upper tubes were completely covered, there was not sufficient power in the suction fan to draw the requisite volume of air through the lower tubes, it having to pass through'a densely packed mass of malt, 2 feet 6 inches thick, and this is particularly the case with wet solid English barley when first put in from the steep, at which stage it is very difficult to get the air through it, and again, later, after sprinkling. Strengthening this supposition is another set of conditions equally tending to yield air to the drum at a point where there is little resistance, and which gives one the decided impression of having been put in as an after-thought to remedy the defect of insufficient air. The drum has a double end at the air intake, which gives a space over the entire end of the drum to receive the air from the large intake tube before it is drawn through the perforated air tubes on the periphery of the drum. At this end there are eight circular
MEACHAM: PNEUMATIC MALT1NGS. 607 holes introduced into the end of the cylinder from this air chamber (see Diagram B, B 2). The distance from the outer surface of the large central perforated tube to the nearest edge of these holes is rather less than 6 inches. For the first few days, until the bulk of the barley in the drum is sufficiently increased by the growth of the rootlets, the grain is only some 6 inches above,the front upper part of the inner tube. This leaves one or more of the orifices more or less uncovered as the drum revolves (see dotted line). By being shut up in a drum of germinating malt with doors closed while the fan is at work, it will be found that the force of air coming through these exposed orifices, although being naturally drawn into the centra] tube directly it enters the drum, is yet sufficiently -strong to blow out a candle at a distance of some 2 feet from the orifice; DlAOBAM C. at a distance of about 6 feet the effects of it are lost, as it has all been drawn into the central tubes by the suction fan. Diagram C is a diagrammatic illustration of what approximately takes place. As these perforated discs are all of them only n short distance from the central air tube, it is probable that from all of them, even under the grain, there is a certain amount of air drawn through as indicated by the arrows at the lower orifice on the diagram. Revert ing again to Diagram A, there are two small pulleys (marked D), the function of which is to keep the iron screen C pressed close up against the ends of the air tubes, and there is a set screw by which the pulley is fixed at the correct distance to run on the surface of the outer plato as the drum revolves. If the surface of the plate were
608 MEACIIAM: PNEUMATIC MALTINGS. true, theso would doubtless answer their purpose, but with (in some cases) ends of cylinders far from being true, these pulleys touch in some places and not others, and two things happen. If the end of the drum be taken off, grooves will bo found where the pulleys have been running tightly pressed hard against the end of the drum, whilst for the remainder of the circumference there is no sign of contact. When the friction takes place, the screen is frequently carried round until the upper holes are completely exposed before it gets free and swings back again to partly cover up the orifice, whilst when the pulleys are not touching, the screen is failing in its work of pressing close up to them. Now let us consider how the above-mentioned defects are likely to affect our malting process. It will bo evident that under these conditions we have not the perfect distribution of the air supply through the malt that has always been claimed for pneumatic makings, nor does the malt get much or possibly any aeration until it in turn rolls over the surface at the top of the central tube (with the exception, perhaps, of the grain at the inlet end of the drum which lies against the air inlet B 2). So long as the weather is cold, and temperatures of germinating drums have no tendency to rise too high, the above-mentioned defects are not felt, for frequent turning is not then required, and in one turn of the drum, occupying some 35 minutes, all the malt, as it falls over tho top of the inner tube, has in turn been subjected to the current of cold air. It is with a high outside temperature of air entering the coke tower, and a correspondingly high temperature in the germinating room, that the inefficiency of the aerating power is felt, for then, in spite of continuous turning of tho drum, with air valves full open, there is difficulty in keeping down the temperature of the malt to anything like normal limits. From the point of cooling alone, the question might naturally be asked: "Why continually turn? Why not let the cool air pass through the malt, and so keep it cool without turning 1" So it might, apart from other considerations, if the air would pass through the body of the malt, but it will not do so, for if the drum is allowed to stand and the air left on, it is only the top layer over the central tube that will remain cool, the malt in the other part of the drum continually rising in temperature. As the malt increases in hulk owing to the growth o
meacham: pneumatic mat/tings. 601) the rootlets, the depth of grain over the top of the centre tube increases, but I am not sure that less air is drawn through owing to the interstices of the wire-like roots than at the earlier stages when the malt lies thinner and the fact that, owing to the clinging nature of the malt due to the interlacing of the roots, the malt, as it falls over the tube, does not maintain the same straight line it did in the earlier stages (Diagram A), but assumes a convex form following the form of the tube, and thus leaves three of the tubes, B, B, exposed the same as in the earlier stages (Diagram A). The end air discs, B 2, are at this stage completely covered, and a thermometer test shows them to be acting in a very restricted manner on the malt within six inches or so of the hole. There is thus a more even thickness of malt over the tube than at the commencement of malting, but that the air drawn through the malt by the fan is still chiefly, if not entirely, through this upper layer is manifest by the fact that the temperature of the malt, although cooled as it passes over the top, rises again in temperature before it again reaches the upper part of the back of the drum before again falling over the central tube to be re-cooled. My experience has been that the drum works better, cooling down the malt quicker, and therefore reducing the amount of turning, when the screen is removed entirely, and the air left an uninterrupted entrance into the top exposed tube. The following may be taken as an example of what takes place in warm weather on commencing to turn and aerate a drum after, say, two hours' standing. Suppose the following to be the conditions existing: Temperature of air outside 78 Temperature of air from coke tower going into drum after being cooled with compressor sprays 60 Apparent temperature of germinating drum (as indicated by air outlet thermometer), say 66 Temperature of drum room 66 "What we might naturally expect, if this cold air wero being drawn equally through the mass of the grain, would be an immediate and continuous drop of temperature of the malt as the large volume of air (6 colder than the malt) is drawn through. This is not,
610 MEACIIAM: PNEUMATIC MALTINGS. however, what takes place; instead of a drop, there may even bo a slight rise in the temperature in the air outlet as the drum starts to revolve, and afterwards no fall of tomporature until after the drum has completed its first revolution. Why this it* so is not difficult to understand, in the light of what has been stated above. The air, being drawn chiefly, or only, through the upper part of the central tube, is raised in temperature directly the drum begins to revolve by reason of the continuous fresh supply of warm malt which now, as it rises from the back of the drum, commences to fall forward from above, whilst the temperature of the air will be further raised after passing through the upper layer of malt, by passing through the length of the inner tube, surrounded as it is by the warm malt. It is not until the drum has made one complete revolution, and all the warm malt in succession has passed over the top of the inner tube, that any appreciable difference is registered by the outlet thermometer, and by the time the malt has been carried up again to the top of the back part of the drum, its temperature will be 1 higher than that which has passed over the tube to the front of the drum. I must now ask your attention to another important point which largely affects this question of temperature, i.e., the temperature of the drum room itself. In the instance given above, the temperature of the drum room was equal to that of the malt, i.e., 66, so that, the temperature of the room was as high as that of the malt. The germinating drums are made of a single thickness of iron plate, which, with an inside wet surface next to the damp growing grain, has, of-course, a high conductivity. Now, with such very poor cooling power as is possessed by the limited action of the cool air being drawn almost entirely through the top thin layer of malt, the influence of the temperature of the drum room itself on the grain within the drum is considerable, and where this temperature is higher the malt will, apart from its own increasing temperature duo to germination, ever bo approximating towards it in spite of the action of the colder air drawn through by the fan ; in fact, the one is neutralising the other. This is the effect the above moderate room temperature would have upon drums containing young pieces whose temperature might be required to be kept lower; whilst, if the temperature of the room rose to anything
MEACIIAM: PNEUMATIC MALT1XGS. 611 near 70 R, the effect would be such as to preclude any low temperature of malt, even with continuous turning. It will at once be seen that, had the temperature of the drum room been lower than that of the malt (say, 60 F.), the effect would have been different, for, with a temperature of room lower than that required for the growing grain, the iron drums will, of course, net in a reverse manner, and tend to somewhat cool down the grain, at all events, the outer layer, towards that of the room. The relation between the temperature ft of the drum room and the required temperature of germination is, therefore, one of considerable importance, and is, especially when working daring high summer temperature or in a warm climate, a potent factor with regard to the temperature of the growing pieces. The evil of having the temperature of the room continually sending up that of the drums is that, with the present defective aeration, it adds to the necessity of continuous turning day and night to try and keep temperature down. This adds greatly to the cost of coal for steam power, and of wear and tear; whilst, especially with young pieces, it knocks off a large quantity of rootlet. Tho remedy is a small cooling machine for keeping down the temperature of the room. All pneumatic makings should bo built of thick walls, with air spaces and with double windows. The conditions obtaining in a cool climate where the temperature of the room is considerably below that of the malt would, of course, be exactly the opposite, and would necessitate tho raising of the temperature of the room by artificial means. This is probably easier and less costly than the opposite operation of cooling by means of refrigerating machinery. There is, however, one point which applies equally in either case, i.e., the impossibility of so regulating the room temperature that it shall suit equally the young pieces which require keeping at u low temperature, and the older pieces at a higher temperature. Further, with the room temperature at too low a point, difficulty is experienced in mellowing whilst withering; or, in other words, withering has to be carried on at too low a temperature, owing to the low temperature of the air of tho room drawn through, to be effective. The arguments used in a contribution to the discussion of Sleeman's paper in 1891 by Dr. Horace Brown on withering, still, to my mind,
612 MEACHAM: PNEUMATIC MALTINGS. retain their full force, for mellowing whilst withering under presont conditions of germinating in drums with a low room temperature is a difficult matter. On the old flooring system, the temperature of the thickened up piece was, for the purpose of rendering the malt mellow and friable, raised to a point higher than that at any previous stage in the flooring. At the same time (as pointed out by Dr. Brown) " there is a constant and large evaporation of water... going on from the surface of every grain of malt." Whilst the temperature of the germinating room has to be kept low enough to suit the younger pieces, the temperature of the withering drum is lowered at once by pulling through it the cool air of the room. The amount of air at withering stage can, of course, be con trolled and limited to whatever extent the maltster chooses by means of the inlet air valves, but if he is to keep his malt sweet at this stage he cannot shut oft' his air supply for too long a period at a time. In other words, there is no difficulty in keeping the temperature of a withering drum down when the temperature of the room is low; the difficulty is in keeping it up sufficiently high whilst giving it sufficient air to keep it sweet. A solution of the difficulty would be the insulation of the drums, so that the temperature of the room could be always kept high enough for the purpose of withering, without affecting the temperature of the young cooler pieces. Mould. There appears to be an impression that with pneumatic makings there is a complete immunity from mould. This, however, is not the case; in hot weather there is considerably less mould than would be the case in malting the same barley under the same atmospheric temperatures on floors, for the following reasons: (1) All air coming in contact with the growing grain up to the time of starting to wither is filtered through the coke tower, and passes along the damp air flues (if the coke in the tower is fresh and of sufficient depth, the air being practically mould free). (2) The absence of damaged grain by feet of workmen, &c. The amount of mould will, of course, depend largely upon the condition of the skin of the barley, but even with the best of screening, and half corn removing machinery, and the latest methods of washing the grain during the steep, spores are carried over with the barley into the germinating drums, and mould makes its appearance during the last few days. During the withering, when the outside
MEACHAM: PNEUMATIC MALTINGS. 613 unfiltered air of the room is drawn through by the fan, the grain is, of course, really converted into a filter bed for the mould spores con tained in the air, and if the temperature is high, there is an increase of mould by the time the piece has gono to kiln, and before it is stopped by the firing. Malt Drying and Curing. We now come to the drying and curing operations, and here, as the construction of the drum is, with one exception, similar to that of the germinating drum, similar defects appear as a result. My experience has been with the double process of kiln-drying first, and drum-curing afterwards, but I should not, as a result of that experience, recommend the arrangement, but should rather prefer a double kiln or two separate kilns side by side, each large enough to take the whole of one day's steep. This would, with four days' drying and curing, give a kiln loading for every two days, to keep pace with the germinating drums, the same as is the case with having drying kilns and curing drums. My reasons for the choice are as follows: (a) I do not consider the drums perfect in their action, for reasons stated further on in connection with the question of diastase. (b) In the case of the kiln only, there would be a great saving of coal for power, and wear and tear of machinery! as considerable power is expended on the curing drums and fans. The gearing for this is heavy. As this is run continuously day and night until finished, the advantage of kilns from this point of view will, I think, be admitted. (c) A reduction in the amount of work at the makings filling the drums from kiln and again emptying them would be avoided, and the work reduced to the one operation of emptying the kiln. (d) Diastatic Power. It is, I think, a general experience that the diastatic power of a drum-cured malt is lower in relation to its colour than is the case with the kiln-cured malt. In considering what may be the cause of this, we may take into consideration that the construction of the curing drum is practically the same as that of the germinating drum, with exactly similar air inlet and outlet arrangements, except that owing to the presence of an insulating space at the air inlet end of the cylinder, the circular holes at the end are not possible. We may, therefore, expect the same
614 MEACHAM: PNEUMATIC MALTINGS. defects in the distribution of the hot air as takes place in the germin ating drum with the cold air. The extent of the defect is possibly less in the curing drums, owing to the fact that tho malt, being dry, would be in a condition to allow of a more free passage of air than is the case of wet grain, but that a similar restriction of the air inlet exists is indicated in several ways: 1. There is tho same open space above tho iron screen as was mentioned in tho case of the germinating drums, and the screens are also very imperfectly held against the ends of the inlet tubes which are above the level of the malt in the drum. 2. By entering a drum when charged with malt and the fan going, the inlet of air from the three exposed air inlet tubes that are above the level of the malt is found to be considerable. 3. If one of the blank doors of the air inlet tubes at the outlet end of the drum be taken off whilst it is below the level of the malt, and a piece of light tissue paper allowed to be drawn in, it does not adhere to the perforated side of the tube, as would be the case if the air were being drawn through it, but at once flies to the other end of the drum, showing that the inlet of air is from the upper partially exposed tubes above, rather than from the lower ones through the malt. 4. If from any cause (such as extra turning on tho drying kiln, resulting in too great a removal of rootlet) the malt should be rather less in bulk than usual, and only cover the upper part of the central tube by an inch or two, it is very difficult indeed to raise the temperature of the malt sufficiently high for efficient curing, the hot air apparently coming almost entirely through the upper tubes, and, as there is so little malt for it to pass through, it has but little power in heating tho whole. Larger fires than usual have to be kept up, and the final curing temperature of the malt is reached with difficulty. %The best temporary remedy in such a case is to put a few bags of malt culms into tho drum, so as to increase the bulk of the malt, and consequently its depth over the upper surface of tho central tube. In this connection it is well to notice the difference in range of temperature between the hot air inlet, the malt, and the air outlet The following set of temperatures shows, in parallel columns, the temperature of the air at different stages of the curing as it enters and leaves the drum, aa well as that of the malt as it passes over the central tube taken by an inside registering thermometer:
MEACIIAM : PNEUMATIC MALTINGS. 615 Temp, air inlet. Temp. malt. Temp* air outlet. f First 8 hours...i 11 I o 160 170 180 100 205 215 220 e 122 130 134 140 150 156 162 o 110 118 122 126 138 144 150 Last G hours...«r 250 250 250 260 270 186 188 190 192 194 168 170 172 174 180 The difference here shown is greater than wo might expect if the hot air were being evenly drawn through the body of the hot malt, for, in that case, the malt would approximate to the temperature of the hot air continuously being drawn through, and the temperature of the air being drawn through would not be so greatly reduced. Instead of this being the case, the body of the malt does not get within about 50 of the inlet, whilst the air in passing through loses about 70 to 80. Notice also that the air comes away 10 to 20 cooler than the registered temperature of the malt If wo now turn to the circumstance of the hot air getting an entrance into the central tube chiefly at the points of least resistance, viz., through the thin upper layer above the tube, we can see how it is possible for the continuous cooling down of the air bjr its passing through the cooler layer of malt that is being continuously brought up from the bottom as the drum revolves. We must boar in mind that the malt, as it travels downwards again with the drum, will have a tendency to lose temperature owing to the absence of hot air, and also to the cooling effect of the much lower temperature of the room acting upon the conductive iron plate of the drum. Temperatures of the malt taken from the bottom and back part of the drum with registering thermometers show this to bo the case. Tho result is that the portion of the malt passing over the central tubo is subjected for a few minutes to extreme heat whilst the hot air is passing through it, whereas the remainder undergoes a process more akin to baking. I am inclined to connect the low VOL. VII. 7. 2 Y
616 MEACHAM: PNKUMATIC MALTIXGa diastatic power of drum-cured malts with the above-mentioned conditions. The curious fact of the hot air coming away 10 cooler than the malt it has been heating may be due to its passage along the central tube after passing through the malt, which, for the greater part of its circumference, is in contact with malt at a lower temperature than that of the top. The relation between the capacity of the germinating drums and the curing drums is a further reason for preferring to finish a malt on kiln instead of transferring to the curing drum. In the hot weather it would be an advantage to reduce the quantity of grain steeped, so as to give greater cooling power. This cannot be dono if curing in drums, as any decrease in quantity gives rise to the difficulties in curing mentioned above. This would, of course, apply in the case of curing on kilns too, but to nothing like the same extent as it does in the case of curing drums. A final word as to mechanical kiln turners. These are excellent in their action, and leave the malt more uniformly level than can be done by the most careful fork or shovel work, but they have one weak point which, unless attention is paid to it, means waste of fuel, irregular drying, and loss of time. I refer to the clear space always left under tho turners when they are stopped. This should bo carefully filled in each time tho turners are stopped, so as to prevent tho heated air from all rushing through this exposed portion of the wire flooring. In bringing to your notice the foregoing characteristics of the pneumatic system of malting, it is not my intention to unqualifyingly condemn them. With respect to the germinating drums, for a hot climate, where ordinary malting is not practicable, the germinating drum or other pneumatic system is indispensable, and in spite of tho defects I have dwelt upon, it is capable of turning out, especially where the tem perature of the drum room can be kept down by artificial means, and a supply of cold water be obtained for the coke tower, a malt of good quality, particularly with barley of the Brewing Californian type. The advantages, in a distant part of the world, of having freshly made malt all tho year round, instead of slack malts at all times tho result of a long sea voyage, largo stocks, and occasionally slack malts being shipped at the end of a season are too great to be lightly set aside.
DISCUSSION. 617 Of course, where a fairly cool water supply is not to hand, water cooled by a refrigerating machine is necessary, and would add con siderably to the cost of malting. During a malting season, in a temperate climate, where there is no excessive outsido temperature to fight against, where temperature of germinating drum room has not to be kept down by freezing plant, and no extra wear and tear of machinery with corresponding con sumption of power by almost continuous turning, the full force of the defects pointed out would not be felt, but it is, of course, especially claimed for the pneumatic system that it can be worked all the year round, and, in whatever climate or temperature, the defective and uneven distribution of the air through the grain, both in germinating and curing drums, is a matter which, in my opinion, leaves room for improvement. Discussion. The Chairman said that the paper was a thoroughly practical one. The author seemed to be of opinion that, at any rate for hot climates, the pneumatic system of malting was the only one possible, but the paper drew attention to a number of mechanical defects connected with the apparatus. Mr. M each am appeared to differ from othor users of drums on several points ; in particular he did not approve of curing in drums, but he, the Chairman, had seen many drum-cured malts and was not dissatisfied with the curing. Mr. Meacbam was also of opinion that mould occurred in drum as on floor, but he, the Chairman, did not think this was so, and he remembered that the late Dr. Morris, in a dis cussion on a paper on the same subject, had expressed his experience that there was remarkable freedom from mould in drum malt. Fortunately, a number of gentlemen were present who had had con siderable experience in pneumatic malting, and others who had brewed from such malt, and he hoped these would give them the benefit of their opinion. Mr. Cuthbert Vaux said he might state his experience during some twenty years on the question of drum malting. To him the paper had been exceedingly interesting, because it referred to climatic conditions entirely different from those experienced in this country. The temperatures which ranged in South Africa were such as he hoped they would never experience in England. Ho was therefore not 2 Y 2
618 DISCUSSION. surprised at Mr^ Mcacham looking on the drum system from the aspect he did ; but he could not think it was at all condemnatory of drums in England, or that his remarks would apply at all, except, of course, to the question of inlet, which had already been raised in this month's Brewers' Journal. It appeared that some one in Germany had brought out a patent to remove this difficulty. When he was malting in Germany and in Denmark none of those difficulties arose, where there were temperatures much warmer than in England. In his experience he had not found the temperatures running away from him, except from some breakdown of machinery or through a deficiency of air such as occasionally occurred. As a rule the temperature could be guided most consistently with drums, according to his experience. It was scarcely fair, he thought, to compare drums in South Africa with drums in England ; and his experience had been always that Hen Ming's drum was the most reliable quantity in the brewery. Whenever a floor malt and a drum malt were put before him, he preferred the drum malt or a mixture of the two; but that was another question. The restriction of diastase which occurred in drum malting required a mixture of floor malt; but from the stability point of view he much preferred a drum malt. If the present Government had not knocked them about as it had, he should certainly put down more drums in the future. There was no doubt that drying drums slightly restricted the diastase, but they had other good points. No doubt if the inventor referred to succeeded in remedying the difficulty about the inlet, they might even yet bo able to use drying drums to advantage. He must say that he considered drum malt to be the backbone of a grist. Dr. E. R. Mohitz said that the piper was a judicial one; the author did not lead them to suppose that drum malt was the end of all things. He pointed out its defects, but he advised that, under the difficult climatic conditions prevailing at the Cape, it was the best system. Ho knew a little about drum malting, and ho thought it all right; but he should not use the eulogistic language about it that Mr. Vaux had used. He could generally tell drum malt from floor malt, for even when well made, it was generally rather hard; and even when dried on an ordinary kiln, the diastase was rather lower than in malts made from the same barleys worked on floors. The general tendency of a drum malt, apart from a certain surface hardness, which probably arose from excessive aeration, seemed to be towards a
DISCUSSION. 619 slight under modification. When mashed in the laboratory they showed rather less extract in tho brewery perhaps it was not so rather low diastase, and rather low carbohydrates. On tho question of mould he agreed with tho author, for he had himsoif soon a con siderable amount of mould in tho drums. In this country there was no particular need to malt on tho drum system; it had certain advantages, especially with high nitrogen barleys which otherwise might tend to run away, but, taking it all round, hi3 experience was that drum malting was not a great practical improvement on the floor system. Mr. R. Chichester said it appeared from this paper that the diastase was very much restricted; and he thought it would bo found an advantage if one raised the temperature of the malt higher than 122 before dropping into the curing drums. If the kiln heats were raised to, say, 170 before running into the curing drum, the diastase would not be so much restricted, as it would not take so long to finish the malt off in the drum afterwards. It was the prolonged baking which crippled the diastase. Mr. E. S. Beavex said he had no practical experience of drum malting, and in consequence was incapable of criticising the mechanical details of these drums. One great difference between drum malting and floor malting, however, appeared to have been generally lost sight of, and that was that in drum malting tho only means of restricting germination was to keep down the temperature of the mass of germinating grain, which was constantly increasing owing to the process of germination itself, by pumping cold air through. In the floor system this result was mainly obtained by exposing tho surface; and the constant evaporation which was going on also kept down the temperature. Moreover, the process of carrying large quantities of air through tho germinating grain necessarily removed tho COo as it was formed. His view with regard to modification was that it was to some extent conditioned by tho amount of CO2 present, and that tho enzymic action which went on, as had been pointed out by moro than one observer, was largely a starvation phenomenon. Ho was under the impression that tho presence of a certain amount of CO2 was favourable to modification. It had often occurred to him as possible, or at any rate, as worthy of experiment, to maintain to a reasonable extent the CO2 in the atmosphere which surrounded the germinating
620 DISCUSSION. grain. It might even be possible and he throw out this suggestion to experimenters to pump round and round the air which was passing through the drums, instead of constantly carrying fresh air compara tively free from CO2 through tho drums. Anyway, in the present drum system the atmosphere in the drum with the air passing freely through it must be quite different in character from the atmosphere surrounding the grain in floor malting. If the floors were noticed rather carefully, one sometimes came to the conclusion that over-turning and over-aeration did as much harm as good, especially as to modifi cation. The paper was very fresh and candid in its treatment of the subject, and, he thought, showed that in this system it was only by constant exposure to a cold current of cold air that undue activity of all sorts, germination, mould activity, and onzymic activity, could be restricted. On the floor system they had all sorts of methods: they could do half a dozen things; they could turn or plough or furrow the grain, aerating it and disturbing the accumulating CO2 more or less as they wished. Notwithstanding the claims made for the drum system, he believed there was on the floor more control over the general conditions under which tho grain was germinating. Mr. G. Cecil Jones asked for the name of the maker of the machinery described by Mr. Meacham, and stated that at least one experiment had been made in the application of refrigeration to floor malting. That particular experiment was not encouraging, and, though ho was by no means prepared tp Bay that it was not worth following up, ho warned maltsters that experiment along these lines would be found costly. Dr. Thorne said that no information was given as to the makers of the apparatus. Mr. A. E. Hewer said he must admit that he preferred good floor malt to drum malt; and he always preferred a mixture of floor malt with drum malt Still, he must strongly corroborate what Mr. Vaux had said, that there was great stability about drum malt. Ho did not think it ever failed in that respect, and that perhaps some of the hardness might be due to excessive turning. But perhaps that was an evil which would come out in a hot climate where excessive turning was necessary, with resulting restriction of rootlet; and possibly that might account for some of the hardness. He always preferred to turn as little as possible.
DISCUSSION. 621 Mr. Hugh Lancaster asked how often the drum revolved. Ho said he understood that one revolution took about 35 minutes* Was it continually revolving during the malting, or only once in so many hours? Dr. L. T. Thorne said ho took it from the paper that in South Africa it was kept revolving pretty continuously. But the suggestion was that it ought not to be necessary; and that probably in England and other places whore there was a lower temperature it would not be necessary. Mr. K. Chichester said the turning greatly depended on the outside temperature and the time of year. In summer, the drums would not stand so long as in winter. In winter, one would let them stand as long as one could, especially at the withering stage. At that stage the less air one pulled through the drum, the mellower the malt. In summer, when one had to pass large quantities of air through the grain in order to keep the temperatures down, one got a harder malt than in winter. He did not see why one should not in winter make as tender a malt in the drums as on the floors, and certainly in the warm weather analysis showed the malt from the drums was superior to malt made on the floors. As a rule, the drums in winter would stand from four to six hours; but in the summer sometimes they would run all day long; it all depended on the outside conditions and the age of tho piece. Mr. S. K. Thorpe said reference was made in the paper that kiln drying barley in the drums was not successful; but he knew of ono case where a drum was put in for the purpose of kiln drying, and it proved a great success. To begin with, by having a hopper over tho drum and one immediately underneath, you could empty tho drum and fill it again in half an hour. In that case you did not get a loss of heat; there was great economy in that way, and you could use any kind of fuel provided it was pure, so that there was moro economy in that direction also. Yon could keep the kilning tem perature to anything you wanted; and there was no delay in getting the temperature up, which there was necessarily in an ordinary floor kiln. Altogether it proved moro economical and effective than kiln drying on the floor, and a drying drum could be filled twice in 24 hours, and the barley dried as thoroughly as if on a kiln double the time.
622 DISCUSSION. The Chairman said he had very little to add to the interesting discussion to which they had listened, but ho would like to refer to one or two matters. First as to the question of kilning and drying in drums: in respect to barley drying there was no doubt that drums were extremely useful because at the commencement of a season, when barleys came in rapidly, it was possible to dispose of them quickly by sweating in drums, which also were quite economical in use for this purpose. Ho had been informed, however, by more than one maltster that drum-dried barleys did not, as a rule, keep very well, and that it was preferable to dry on a kiln such barleys as would be held over three or four months before steeping. In regard to the matter of extract, ho had had an opportunity spread over a number of years of comparing laboratory and brewery extracts from drum-made malts, and he agreed with Dr. Moritz that the laboratory extract was frequently a little low, but the brewery extract did not suffer equally, in fact, with a drum malt the difference between laboratory and brewery extract was, as a rule, smaller than with other malts. With regard to the general question of curing in drums as distinguished from kilns, Mr. Meacham was evidently of opinion that drums should not be used. Ho did not share that opinion, but quite agreed with the desirability of drying on a kiln. He was of opinion that curing might quite satisfactorily be carried out in drums. It was true that drum malts were, as a rule, low in diastase, but this was not due to the curing drums, for the diastase was equally low whether cured in drums or on kilns. Looking at the whole question, he thought experience had showed that the drum system of malting possessed a good many advantages. It was not, perhaps, all that was originally claimed for it when it was first introduced, and it had not, as was at one time predicted, supplanted the floor system. Excellent malts were, of course, produced on floors under favourable conditions; but, unfortunately, they could not command the weather, and were not in the relatively independent position which existed when working in drums. Most of them would agree, however, that floor malts made under ideal conditions were just as good, and, perhaps, a little better than drum malts. They were indebted to Mr. Meacham for sending over this paper, which was just the character desired at their meetings. And, with their permission, he would send him their thanks. They were also much indebted to Dr. Thome for reading the paper so clearly.