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.
(Contributed by Hedley C. Queree)
The number of storeys of which a bakery is composed will regulate the placing of the various machines. Generally speaking, it may be taken that the flour is stacked on the topmost floor, and that this is shot into hoppers which are connected either to blending machines fixed just below the ceiling, or else to kneading and mixing machines placed on the floor below.
The ground floor accommodates the dough-tables, dividing machines, and ovens. It is therefore necessary that the construction of the floor itself should be of such strength that a heavy dead load can be carried with safety. The concrete surface should be made with an easy gradient to enable it to be swilled down, for according to the Factory Acts all traps and drainage must be kept outside the building.
In small bakeries, or in localities where land area need not be considered, it is more convenient to place the kneading machine and ovens together on the ground floor.
The success of a baker greatly depends on his ovens, and great care should be exercised in the selection of these. This choice will regulate the construction of the bakery, and a change of opinion on the part of the baker-client would probably result in a radical change of planning, which is much to be avoided.
The ordinary builder-constructed farmer's or baker's ovens, as found in most places which date some way back, are scarcely ever built now, except perhaps in farmhouses, where the spirit of conservatism is prevalent. The modern baker would certainly never dream of building such an oven where he could obtain a specially constructed one as described later. However, Fig. 102 represents the plan and section of such an oven, consisting of an inner skin of 4 1/2-inch brickwork laid with a very fine joint of clay mortar, and an outer skin of 9-inch brick or stonework built in ordinary lime mortar. Between these two walls is inserted a 2-inch thickness of sand, which would also be carried over the 9-inch brick arched vault.
The general contour of the interior of the oven is pear shaped, with the door opening at its apex and the firing arrangements at one side or other of oven door. The flame and heat travel around the oven as shown by the arrows on the plan, and away by the flue. The doors, plates, and gratings are made of cast iron.
The splay at each side of oven door should be made of a good width, so that facility of movement will be given to the " peel " to work round to all sides of oven. The " peel " is a flat wooden spade with which the bread is placed in or drawn from the oven, technically known as "setting" and "drawing." The space beneath the iron sole plate is generally devoted to stocking coal, whilst that beneath the furnace grating is for the reception of ashes.
The sole or floor of the oven is made of good stout tiles, bricks, or stone, which must be of a very fine texture and free from grit of any description; as there is a continual friction from the action of the peel, which would cause trouble if the sole surface were not perfectly even in its wearing qualities.
The best place for the oven is in the corner of the bakehouse, so that the flue may pass conveniently from over the oven door into the wall alongside. Where this is impossible and the oven is merely backed against a wall, the flues would have to be carried by means of a gradual slope to the wall at back, an arrangement which should be avoided, as it becomes both an unsightly object and affects the drawing capacity.
When the bread is in the oven the door is left open, and an iron blower is placed on the iron sole plate, as shown dotted on plan, so enclosing the flue in the oven. This blower is made semicircular in shape, of stout sheet iron with two handles, and a glazed inspection hole through which the baker can watch the baking process.
The drawing shows a low vault roof: 18 inches at its springing level and 2 feet at head. Many ovens have been made with a higher vault, but it has been found that bread will not rise so well in these as in the low-crowned oven. The top of the oven can be utilised for setting dough, etc. A very convenient arrangement is to place a water tank above the furnace, fitted with service pipe and draw-off cock.
Ovens are either internally or externally heated, the former method as just described being used in farmhouses and older bakeries, but now rarely - if ever - built in a bakery of any size. The externally heated ovens are those fired by steam pipe or hot air. The former are economical and continuous, but require careful and undivided attention, as well as freedom from a chimney inclined to down draught.
Hot-air ovens vary considerably, the majority being extravagant in fuel and difficult to regulate, but the better ones are more economical than steam-pipe ovens, and are not affected by down draught or irregular attention. Steam-pipe ovens in their turn may be heated either by a furnace, fed by coal or coke, which produces a certain amount of dust and dirt and requires regular stoking, or, as is becoming more generally adopted, by gas, which is regular, continuous, and requires little or no attention.
Ord1nary Builder-Built Oven.
Ovens are generally fired at back, side, or front or bakehouse; preferably the former, as this will allow of the extension of the range of ovens at any future time. Space at the back of oven must be allowed for the stoking arrangements, the floor being at a lower level than that of the bakehouse.
A steam-pipe oven requires a greater space than one fed by hot air, for the former has its furnace added to the length or width of oven, according as to whether it is fired from back or side, whilst the latter has its furnace beneath. The stack to these ovens contains flues varying from 6 inches circular to 14 by 9 inches rectangular.