MEETING of the LONDON SECTION, HELD at the ENGINEERS’ CLUB, COVENTRY ST., PICCADILLY, W., on MONDAY, FEBRUARY 14th, 1927.
Mr. James Stewart in the Chair.
A DISCUSSION ON FERMENTING VESSELS
was opened by Messes. E. B. Collier, A. Cotching, L. G. Simpkins, and R. J. B. Storey
WOODEN VESSELS.
By A. Cotching
During the last few years many complaints have been made with regard to the use of wood for fermenting vessels, which, to a great extent, could have been avoided if they had been made of suitable material, had received proper care and treatment, and not remained in use long after the surface of the timber had become contaminated. Many kinds of wood have been used. In the past oak and fir were most popular, and although they were both hard and durable, they were not quite ideal timbers for the purpose, as the wood contained a number of large knots, was coarse in grain, and with the constant cleaning and scrubbing of the surface, had a tendency to tear up and become rough.
American White Cedar has also been used with success in some breweries, but as these trees do not grow to a great height, the wood was full of small knots which present rough places and was not pleasing in appearance. Teak has not been used to any great extent. It has a hard surface and is very durable and would appear to be more suitable for the purpose than the other timbers mentioned. It will stand heat well and has been more used for mash tuns and other similar purposes. Of late years British Columbian Pine has been used for making fermenting vessels. It is fairly hard and free from knots, but the surface, when finished, owing to the nature of the grain, cannot always be planed as smooth as was desirable.
New Zealand Kauri Pine was first introduced into England about 40-50 years ago, and the timber has proved itself, in every way, the best and most suitable for Fermenting Vessels. It is hard, close grained, free from knots, and when made up has a pleasing, hard, smooth and silky surface. It is obtainable in large, wide planks, the trees growing to a great height with trunks of large dimensions. Precautions should be taken to ensure that the wood is cut from the living forests of New Zealand, as in recent years a timber has been imported and sold as Kauri Pine, which has been lying buried in the swamps, probably for some hundreds of years, and that timber, although similar in appearance, is not suitable for Fermentation Vessels owing to its absorbent nature and other defects, which appear after being in use a short time.
The greatest efficiency from a Wooden Vessel can only be obtained if the timber used is thoroughly weather-seasoned, carefully selected, free from sap, and other defects, and is made by skilled mechanics. In constructing and erecting, care should be taken that there should be an air space all around the vessel, also that gangways and splashboards should not be fixed to the sides as, when washing down, the wet is liable to get between and cause rot. All the bars and bolts inside the vessel that are likely to come into contact with the wort should be of Muntz’s, or similar metal, and not iron, as the latter has a detrimental effect on all timbers, but more especially Kauri Pine. The outside ironwork should be galvanized; the extra cost of which is not great.
Round vessels have many advantages, as having no corners, they are easier to clean and have a longer life than squares.
They could also be left out of use for a longer period without fear of leakage. On the other hand, they occupy more space, and for this reason the square shape is generally used.
Where space is limited, it is perhaps better to have a double or treble vessel in preference to single ones, where it is only possible to have a few inches between, for if they are well made and erected, there should be no danger of leakage from one compartment to another.
When a new vessel is ready for use, it should be seasoned by using a small quantity of common salt and cold liquor. New wood has, in the past, been frequently ruined by too drastic measures, which softened the surface and injured the fibres of the timber.
In the cleaning no difficulty should be experienced if, directly the vessel is empty, the sides are well soaked with cold liquor. No hot water or cleansing agents should be used, as both tend to make the surface of the wood soft and woolly. The cleaning process should be finished off by a good scrubbing with fine pumice powder, which will prevent to a great extent the formation of scale. Finally, the vessel should be sprayed with a suitable sterilising agent and allowed to stand, before the final wash out.
To prevent yeast adhering to the wood above the beer level, the surface should be coated over with a preservative, in the form of a paste. An empty vessel should never be left with liquor on the bottom, as this will soon go stale and effect the wood. From time to time the vessel should be allowed to remain out of use for a few days. This will help to keep the surface of the timber hard, and also afford an opportunity for inspection. If scale is found to be forming in uneven patches, it should not be scraped off, but the whole vessel should be planed. All parts of the outside of the vessel should be kept clean. A thorough painting once a year with raw linseed oil will keep the wood in good condition.
The life of all timber vessels depends mainly on their construction, position, use, and treatment. Under normal conditions, after 20 to 25 years, the pores of the wood in places are likely gradually to become more open, caused by the slow withering of the tylese3, which permit bacteria to find their way into the timber and so constituting a source of infection, which is very difficult to combat.
ALUMINIUM AND COPPER VESSELS
By R. J. B. Storey
The Speaker said he supported the doctrine that there should be no wooden vessels in a fermenting room. Some sixteen or eighteen years ago, it became obvious that the wooden fermenting vessels in the brewery he was connected with were on the wane. They were made of red deal or white cedar and had been in use in most cases for 12 or 18 years, and drastic treatment with pumice, hot water, sulphur dioxide and steam in an attempt to obtain sterility had rendered the wood soft and woolly, and constant planing failed to secure a passably smooth surface. At that time all the skimming squares were copper-lined, and the linings—put into red deal squares, which had shown signs of stringent cleaning methods after ten years’ wear—had given every satisfaction, and there was, moreover, no trace of yeast poisoning by copper. There was so little information available as to whether copper poisoning was due to impurities in the metal used or whether certain types of yeast were particularly susceptible to copper, that it was necessary to search for some other material, and he investigated the claims made for aluminium, which was then talked of as a suitable lining for fermentation vessels.
At his brewery an aluminium lining—and he believed it was the first used in this country —was put in seventeen years ago and seemed as good to-day as it was then. In a year or two, all the fermentation vessels were similarly treated, precautions being taken to provide an escape for any moisture which might be between the vessel and its lining. So long as alkalis and mercury thermometers were avoided and the vessels were left clean, and as dry as possible, there was nothing to fear with aluminium, and they could be scoured with fine pumice just as freely as copper vessels. Should, however, the vessel be likely to be idle for some months, it was advisable to protect it from air by a coat of suitable spirit varnish. Any scale which might have formed could be removed by scouring with dilute nitric acid. The vessels were all fitted with hanging copper attemperators, so that there was no question of contact between the two metals. In the early aluminium vessels, a little trouble was experienced by moisture settling in the joint between the aluminium and the gun-metal outlet, but modern methods had overcome that difficulty, and the outlet to a modern lined vessel was perfect as that of any other metal vessel.
The life of copper fermenting vessels seemed to be almost everlasting, but—if kept burnished—they’re required more labour than aluminium, though—in fairness to copper—he must admit that his beers only remained from 12 to 24 hours in the aluminium, as against 4 to 6 days in the copper vessels. There always was the possibility of copper poisoning of yeast. To some extent this could be guarded against by bronzing the copper with an alkali after cleaning, but more thoroughly by coating the vessel all over with Tetley’s enamel or with Dukeron; but either of these enamels would have to be renewed fairly often as scrubbing gradually removed it. Tinning would no doubt get over the poisoning danger, but the renewal of the tin would be difficult and expensive.
Those who were keen on a smart fermenting room should be warned against painting or varnishing a metal lined wooden vessel; to keep air from both sides of the wood was to invite rot. His remarks had been confined to copper and aluminium lined vessels, but, after all, lining might suffice, but it was not the ideal; personally, he was in favour of solid aluminium or copper fermenting vessels; properly lagged with a distinct bias towards the former.
Mr. W. J. Watkins said the chief trouble he had experienced with Kauri pine was leakage if the vessels were left empty for 48 hours or more. Some brewers considered it advisable to leave such vessels empty for a few days if possible as it was beneficial for them to be exposed to the air, but he had to fill them on the third day or they leaked. He did not think a good case had been made out during the discussion for concrete, and apparently the blistering, the possibility of fracture and the renewal of the lining were the chief troubles. He did not like slate fermenting vessels as he had found the joints give trouble and they were very liable to crack. Steel vessels were far too expensive for most of them, and again, there was the joint question, and if the vessel had to be made in one piece there was a limit to the size. Moreover, the loss of heat by radiation was very high, and damaged glass lining was difficult to repair. The general consensus of opinion appeared to be in favour of aluminium and it seemed the easiest material to keep free of scale. Wooden vessels could be kept fairly free of scale by the use of pumice, but the wear caused by such cleaning was heavy.
Mr. H. Lloyd Hind said he gathered that the choice of material for fermenting vessels depended on the weighing up of the pros and cons of all those which were available. Wood and slate were evidently approved of, judging by the remarks which had been made. Kauri pine was an excellent wood, but it was necessary to emphasise the danger of using “Swamp Kauri” which had lain buried for many years and in consequence was very porous. Yeast poisoning from copper vessels certainly occurred, but rather infrequently. Many breweries carried on for years with the same strain of yeast either in blackened or polished copper vessels. Poisoning was most likely to occur when the yeast had been weakened through some other cause.
It was desirable to have enamelled steel vessels in one piece, and doubly enamelled, but it was often difficult to get them into the brewery. Concrete he had seen giving every satisfaction when lined with “Ebon.” A distillery company he believed was experimenting with a form of concrete incorporating pitch known as “Prodorite,” and had found it useful as a vessel in which to heat sawdust with strong acid for conversion into sugar. As it appeared to stand this very drastic treatment satisfactorily, he had great hopes that when further developed it would be of use for fermenting vessels. With regard to hammer hardening of the surface of copper, he would like to know whether the surface of copper which had been properly hardened became after years of use softer, and more likely to have a deleterious effect on yeast.
Mr. J. Auld said his experience comprised wood, copper lined and aluminium vessels. The first-mentioned were made of red deal and lasted six years, and it then became necessary to line them with copper. The cost, including the removal of the attemperators, was £1 per barrel. When first using copper lined vessels he did not stipulate that the copper should be hammer hardened and copper poisoning of the yeast occurred. New copper lined vessels which were hammer hardened gave no further trouble with poisoning. He was satisfied with aluminium vessels, but they required rather more cleaning than copper.
Mr. A. P. Heard said he was opposed to the use of wood vessels and wherever possible this material was being replaced as quickly as possible by aluminium. He agreed with Mr. Johnson that there was a certain amount of character given to beer fermented in wooden vessels which could never be obtained from metal vessels; some of these characteristics could, however, be well dispensed with. He had noticed that the beer of certain breweries had a character which possibly the inhabitants of that district who consumed the beers liked and would object to if it were changed. The cleaning of aluminium vessels was not a difficult matter—the use of nitric acid occasionally, a certain amount of pumice, a wire brush and appropriate labour would keep aluminium perfectly clean.
Mr. C. A. Finzel asked Mr. Simpkins if the slate vessels he used suffered from pitting. He agreed with what Mr. Cotching had said about Kauri pine.
Mr. A. W. Kibble remarked that he was an advocate for copper vessels. Old wooden vessels ought not to be lined but should be pulled down and replaced by properly built copper vessels. Slate was a good material for fermenting vessels, but the upkeep was slightly heavier than wood or copper, also the increased weight and expensive foundations were an objection. He had used aluminium for priming vessels; it was satisfactory except for a slight discolouration.
Mr. J. G. Daniell said he was of the opinion that beers with most character and outstanding merit came from those breweries which used unlined wooden fermenting vessels, and that those vessels still held their own if they were properly looked after and renewed when required.
Mr. C. A. Warren said that beers from copper lined vessels frequently contained as much as one-sixth grain of copper per gallon, and he would be interested to know whether any of the authors were of opinion that the copper flavour sometimes came through to the beer. He thought he had noticed such a flavour in some light bottled beers.
Mr. H. Heron said experience obtained in several breweries gave ample proof of the direct poisoning effect of unsatisfactory copper on the most vigorous yeast. Immunity from copper poisoning appeared to be due to the use of copper, the surface of which had been efficiently hardened. Such copper could be burnished without apparent harm although it was possible that after a time continued scouring would eventually cause trouble. Cold hammered copper gave the best results in the brewery. He could assure Mr. Storey that his suggestion of tinning the surface of copper lined fermenting vessels would undoubtedly produce a “tin haze” in the beers fermented in them. He considered that the efficiency of wooden fermenting vessels depended entirely on the purity of the atmosphere and its freedom from more dangerous types of organisms. In cases where the air entering the brewery was subjected to contamination with malt dust, wood owing to its liability to become contaminated could never be an entirely sound proposition. He could not agree with the speakers who had stated that the character of beers brewed in wooden vessels was always superior to those brewed in other vessels. He had seen beers brewed in copper and aluminium vessels which possessed as good and even better character than those produced from wood. The views expressed might have been true under pre-war conditions but the lighter gravity beers of to-day were so sensitive to changes and infection that the best results could only be obtained when fermenting vessels were used which could be rendered sterile.
Dr. Seligman said the late Sir George Beilby had found that the surface treatment of metals resulted in a superficial layer of what was termed vitreous-amorphous matter. The surface of any metal so treated had a vitreous appearance and it was in the same metastable condition as glass. It was under strain and the tendency was for it to revert to the crystalline state. This reversion would take an immense time and it could not alone account for the behaviour of hammer hardened copper linings. The vitreous surface from one point of view was highly resistant because it was very smooth and a perfectly smooth surface was comparatively immune from attack, owing to the absence of points from which gases caused by such attacks could be disengaged. On the other hand, being under strain it was more liable to attack, and it had been found that many metals were more readily attacked in the hardened than in the unhardened crystalline state. These two circumstances operating together might account for the cases cited by Mr. Heron.
Mr. E. B. Collier remarked that he differed from the statement that the best beer was brewed in wooden vessels. Good beers could be brewed from copper and aluminium lined vessels, as well as from wood. A good deal could be said in favour of cement or ferro-concrete vessels. It had been stated that copper lining to be safe should be enamelled, and aluminium vessels required watching for pitting. If cast iron vessels were used there would presumably be joints and he regarded joints as troublesome, and there was, in addition, the danger of iron contamination. He had had considerable experience with copper lined vessels and had never been troubled with yeast poisoning. The fact that the use of preservatives had been limited, in his opinion, ruled out the use of wooden fermenting vessels.
Mr. A. Cotching, in reply to Mr. Storey’s question said he had had no experience with teak for a fermenting vessel, but he had used it for a mash tun with good results. He did not consider the lining of an old wooden fermenting vessel a wise procedure, it should be replaced with new wood or a new vessel should be made of some other material. He had experienced no difficulty in obtaining carbonic acid of 99 per cent, purity from wooden fermenting vessels, which were constructed for that purpose, the front opening being closed by a shutter with a rubber joint. As the thickness of most timber used for fermenting vessels was 3 ins., planing could be done many times, for the amount planed off on each occasion was very small.
Mr. L. E. Simpkins said he had never had a slate vessel flake, except on one occasion which was probably due to a heavy blow the vessel had received. He had experienced no trouble with jointing, and he had never observed a slate vessel leak.
Mr. R. J. B. Storey said he had used “Bar Acid” on iron vessels and had found that unless that material was cleaned off every two months the iron came through. His bottling vessels were watched and nearly every filling examined for iron content, and it was found that if used for over two months there was invariably one-seventh grain of iron per gallon which gave the beer a distinctly inky flavour. He could not agree with Mr. Cotching about the non-porosity of wooden vessels. Teak had been mentioned as suitable for fermenting vessels, and it would be interesting to hear the experience of users of that wood. He feared the flavour of it. In lining vessels, he had found it a convenient practice to cut out the rotten timber, and to fill up the spaces with Portland cement; this, however, could not be done with aluminium.
Crescent City Brew Talk 