This section is from the book "Modern Buildings, Their Planning, Construction And Equipment Vol6", by G. A. T. Middleton. Also available from Amazon: Modern Buildings.
The ovens themselves, as made by special bakery engineers, may be divided into two classes, namely, drawplate and peel ovens, the former being used in preference to the latter where space allows. In the lower part of Plate III. is illustrated an interior view of Messrs. Morris & Sons' bakery at Richmond. Drawplate ovens made by Messrs. Werner, Pfleiderer, & Perkins are shown, with a peel oven on the extreme left. The upper part of Plate II. shows the electric machinery.
The drawplate oven, as the name implies, is one where the bed or bottom plate is made to draw out. It consists of a brick-enclosed chamber heated by steam pipes above and below the baking space, which pipes contain a certain amount of water and are hermetically sealed at both ends. The fittings are made of heavy iron, as is also the bed of the oven, which runs on ball bearings and with telescopic motion on the framework, which in its turn runs over a special track fixed into the concrete floor. The iron door is made close fitting, and is raised by means of chain and wheel at side, its action being counterbalanced by a weight. A clock is generally placed above these ovens, which is set at the time at which bread is introduced, so that the attendant can know accurately the time taken for baking.
The peel oven is that in which the bed-plate is a fixture, and the doors are made to open on hinges or to slide, the bread being inserted into the oven by one of the many kinds of wooden shovels known as " peels."
The drawplate oven possesses the advantage that it can be loaded very expeditiously, and inspection of the whole baking can be easily accomplished. On the other hand, where the space in front of ovens is limited, then the advantage of the "peel" or fixed oven predominates.
Ovens may be made to suit any particular arrangement and for any kind of bread. A general idea of the construction is shown in Fig. 103, the point of difference being the flat and sloped bed. The external walls are finished off with glazed brickwork in one or more colours as fancy dictates, and this can with advantage be carried around the sides of the bakehouse itself, or where cost has to be considered the walls may be cemented and painted.
The ovens may be arranged in various combinations, as, for instance, with double decker drawplates, i.e. one drawplate above the other, each with its set of rolling tracks; or the same arrangement with two peel ovens; or again, with one peel oven and one draw-plate one above the other. An oven used for French and Vienna bread is shown in section in Fig. 103. This is as made by Messrs. Joseph Baker & Sons, the main difference from an ordinary oven being that the chamber has a lower roof, whilst the sole is inclined and is generally made of glazed tiles. These ovens may be built one above the other, both with inclined soles or else one inclined and the other level. They can be supplied, if so desired, with flash heat, besides the ordinary steam heat, which is said to give a delicate colour and crisp crust to the bread. Flues are introduced into the oven through which the heat from the furnace can be drawn whenever required, being under entire control of the baker in attendance.
Continous French & Vienna Bread Oven.
Messrs. Thomas Collins & Co. make ovens which differ in construction from those above described. The oven and furnace (Fig. 104) occupies a floor space of 9 feet wide and 11 feet deep. In this the ovens consist of one large lower oven 8 feet square, and two smaller separate ovens above, each 8 feet by 4. The combination may be varied from one oven to four single ovens in two tiers, the single oven being 5 feet wide. When a mixed trade is done each of the compartments may be used for different purposes, and warmed at different temperatures.
As will be seen by the illustration, the oven itself is composed of iron, which is in two thicknesses separated by a layer of non-conducting material. The space beneath the oven is utilised as a proving cupboard.
The oven, on account of its structure, adapts itself to situations where it is expedient to place it on the first floor of a building.
The heat is obtained by means of a fuel fire in the furnace at the back, and a series of tubes is carried above and below the baking compartments, a steam boiler is placed above the fire, which can supply steam to the ovens and prover.
A portable oven may not be out of place. One made by Messrs. Chas. Portway & Sons is shown in Fig. 105. It is 2 feet 8 inches in depth, 2 feet 8 inches to 3 feet in length, and 4 to 5 feet 6 inches in height. It consists of double cased iron, packed with non-conducting material. Each shelf has its own door, which drops to a horizontal position when open, so becoming a continuation of the shelf. The fire-box, which extends to the rear of the oven, answers the purpose of a combustion chamber. A movable grate is suspended under the fire-box, and the action of heating is as follows: Air enters through the circular ventilators at each side of fire-box, becomes heated as it passes round the stove, rises in the heated chamber, and reaches the shelves by apertures in the plates, passes over the goods, and down again to the front of oven to the stove, where it is reheated. The flue pipes shown are connected to the nozzle in the stove, and as they are branched in two they radiate a greater amount of heat than if one only were used.
Ovens may be built to any size, but that usually adopted has a sole plate 12 feet long and 6 feet wide. Where the floor of the flour store is not of concrete it should be cross-boarded, so as to prevent the flour from passing through. The flour is stored in sacks, and these are emptied into a large wooden hopper, communicating with either a blending or a sifting machine. The latter (Fig. 106), while fixed to the ceiling, consists of a steel shaft covered by a spiral brush, its action being to brush the flour against a sieve at the bottom of the machine, so removing any string, fluff, or foreign matter, which it carries to one end and there ejects into bags or other receptacles. It is 3 feet 6 inches long, including pulley, and 2 feet wide. The flour is then dropped into a canvas shoot, which conveys it to the kneading machine, where yeast and water are added. This machine consists of a heavy iron framework, the kneading trough being rectangular on plan and having a double semicircular bottom, into each part of which a beater revolves. These act in opposite directions, so affecting a very thorough kneading of the dough.
Fig. 107 shows a machine fitted with two beaters, which is usual, but such machines are also made with one beater only, where the output is small and expense a consideration. The average space required would be about 6 feet 6 inches long by 6 feet deep, and 6 feet 6 inches high.
The kneader is tilted up by means of the hand wheel at back, the whole revolving on its front edge, so easily tipping out the dough into a travelling trough which is made to suit its length and capacity.
In bakeries of average size the flour is bought ready blended from the millers, but where this has to be carried out by the bakers themselves the act of mixing will have to take place before the sifting and the kneading, the flour being conveyed from the blender to the sifter, and then by canvas bags to the kneader. The same style of machine as the kneader may be used for blending or mixing of flours.
The dough is left to rise in the trough, and then is taken to a moulding table or a special machine, - the table being of a convenient length and width according to number of bakers, and fitted with drawers into which the moulded pieces of dough may be placed away from the cold air, which would have the effect of forming a crust on them. Instead of putting the dough into these drawers, it may be placed on a travelling rack, holding a number of trays, each provided with a covering canvas cloth and conveying handle at each end, so that two operators can easily tip the whole tray load of moulded dough on to the oven plate when this is made of the draw-out pattern, - which expedites matters very considerably.