JOURNAL of the INSTITUTE of BREWING
published 1935
CASK LINING
By A. F. Johnston
The efficiency required in our industry has attracted the brewers’ attention to the question of their cask plant, and the necessity for improving its condition and soundness. The vexed question of cask lining is, therefore, receiving considerably more attention than formerly.
An efficient lining should be highly adhesive and elastic, it should possess a hard, smooth surface without porosity, odour or flavour, and it should not present any difficulties in its application or tend to dis-organise the cask plant. Difficulty in obtaining these conditions has undoubtedly been the cause of failures in the past, and the reluctance of brewers to change their present methods. The fact that brewers have abandoned the wooden fermenting vessels and replaced them with metal or metal-lined vessels, shows the trend of opinion with regard to the use of wood in direct contact with beer. This has also had the effect of changing methods of cleaning, according to the nature of the metal or lining of the vessel.
We have not advanced so far as to adopt metal for cask linings, but there should be no argument against an efficient lining if this be forthcoming.
Mr. J. W. Huxley has, for a considerable number of years, made a close study of cask lining, and has succeeded in using a pitch lining conforming very closely to the conditions mentioned above, and which is giving complete satisfaction under general trading conditions.
Many other types of lining were tried out without success, before this particular one was adopted. An important advantage of this lining is that any sedimentary yeast or hops remaining adhering to its surface can be easily removed, together with all deposited matter, by one simple process. After re-pitching, the cask is rendered perfectly sound once more at a cost less than it would take to unbend and scrub.
Method of procedure — Two machines are required, a pre-heater and a pitching machine.
The pre-heater consists of an enclosed iron vessel shaped at the top to carry the cask— with a burner protruding sufficiently to enter the bung-hole when the cask is placed upon the stand. The burner is fed by coal-gas and air and is regulated by the operator. A single-burner pre-heater consumes approximately 60 cu. ft. per hour, the floor-space required is 2 ft. by 2 ft. and the weight is 2 cwt. The name of the burner when correctly regulated does not protrude more than 1½ ins. and therefore, cannot touch any part of the cask. Bung-bushes cannot become overheated, as they only come into contact with the cold feed pipe. This pipe is naturally kept cool by the cold air and gas passing through it, and therefore, has a considerable advantage over steam-heater pipes. The machine rapidly de-pitches any casks that require re-pitching or will dry out unlined casks without the necessity of un-heading.
The pitching machine has no complicated or moving parts to get out of order, compressed air being the only power necessary to operate it. Coal-gas is advised as a means of heating as this provides an excellent temperature control and is entirely safe.
The plant consists of a cast-iron pitching kettle divided into an upper and a lower chamber—the lower chamber containing the pitch and the upper chamber receiving any surplus pitch from the cask. The pitch in this upper chamber returns to the lower one by a non-return valve, when pressure is released in the latter. The non-return valve automatically closes when 8 to 9 lb. of air-pressure is put on the lower chamber for the purpose of forcing the pitch through the nozzle into the cask. A safety device ensures that no pitching operation can take place without the cask being in position. The operator has only to move one lever to carry out this work. To remove the smoke arising from the pitch—an operation which takes place immediately after pitching—air is admitted into the pitching nozzle by a movement of a second lever.
The working temperature of most pitches is between 350° and 400° F. It should not go below this temperature, and although it appears to be high it should be remembered that the pitch is deposited in a thin film on the surface of the cask and cools too rapidly to have any harmful effect on the wood. The writer can state definitely that the life of casks treated in this way is certainly longer than that of an unlined cask.
A point to emphasise in pitching is the importance of having an ample supply of air at a fairly high pressure to drive out all the pitch smoke and volatile constituents which might transmit flavour to the beer. Air at a pressure of 15 to 20 lb. per sq. in., used for 45 to 60 seconds is found to be sufficient for the purpose.
The lining will set in approximately 3 hours, after which, as a safeguard, the casks may be washed with liquor at 130° F., and after the draining period they are ready for the racking cellar.
“Stinkers” and musty casks may be used without fear after being pitched, and should a pitched cask be found to have become foul, it is only necessary to de-pitch and then re-pitch to make it sweet again. All casks passing to the racking cellar are carefully examined, and it is only when they fail to pass that re-pitching is necessary. As a precautionary measure, however, all casks or export, stock ales, and those intended for bright carbonated beers, are re-pitched before use.
The cost of pitch is approximately 4¾d. a pound, and as a barrel or 2 kilderkins require 1½ lb. of pitch, the cost for a barrel is 7d. and that for a kil is 3½d. A single pitching-machine will line 30 casks per hour.
The temperature of the washing liquor for these lined casks should not be higher than 130° F., as the softening point of pitch which has been subjected to a temperature of 400° F. is 135° F. This does appear to be a very low temperature for the washing, but it should be realised that only a perfectly smooth, hard surface is being dealt with and that all the sources of infection, such as the pores of the wood, etc., have been eliminated. The results obtained in practice have proved perfectly satisfactory under the conditions described. This method of washing showed a considerable economy compared with the cost of washing unlined casks and should be balanced against the cost of re-pitching. The life of the cask is considerably extended owing to the reduction of “throw-outs”— and cooperage is reduced to a minimum. Experience gained in treating casks in this manner has shown that not one cask per month is returned to the brewery where the beer has been spoilt by the lining and stock ales stored for a period of twelve months give excellent results, while no difficulties or complaints have been encountered in the export trade. Although export casks are returned in the poorest possible condition, under the system of lining described they can be quickly returned to trade.
An advantage that lined casks have over unlined casks is the fact that they are gas-tight, and that is of special significance when light gravity beers are concerned. Such beers, as a rule, have only sufficient gas when they are sent out to keep them in proper condition for a short period, and any loss of gas cannot subsequently be made up by the beer itself on account of its low gravity.
Another advantage that may be claimed is that there is no loss of beer due to absorption by the wood, and during the past two summers such loss has been a cause of com plaint to many brewers. Consistency is the aim and object of every brewer, and a cask which will ensure this is certainly worthy of consideration.
For the service of chilled and filtered beers in bulk a gas-tight cask which is also sterile would remove any uncertainty respecting condition, whilst it would tend to conserve brilliancy by its freedom from infection.
Crescent City Brew Talk 