In the year 1830 a patent was taken out by Mr. Robert Hicks for "an economical apparatus or machine to be applied in the process of baking for the purpose of saving materials;" and for carrying this invention into effect on the great scale, the Metropolitan Bread Company (now extinct) was established. The saving of materials mentioned in the title just quoted, had reference to the saving of the vinous spirit which is generated by the fermentation of the dough, and is given off chiefly in the process of baking. This spirit, when duly rectified, is pure alcohol, and the quantity thus* obtained from bread has been variously stated; but we believe it amounts to nearly a gallon per sack of flour when the oven is perfect, and the joints well luted. To make a chamber or retort so impervious as to carry on the process of distillation as well as that of baking, would, of course, be impracticable with such porous and friable materials as brick and stone; Mr. Hicks, therefore, adopted one of iron, laying inside upon the bottom a floor of bricks, that too scorching a heat might not be communicated from the metal to the bread; a fire is made under the oven, at a proper distance, and brick flues communicating with the fire chamber, are carried around the outside of the oven, so as to envelope every part.
The door of the oven is made to fit it accurately by grinding, and is brought into close contact by a transverse bar and screw, in the manner of closing the mouths of retorts. In the centre of the top of the oven a large tube, or neck, is fixed vertically, extending from the brickwork which covers the iron chamber; in this tube the vapours from the bread are collected, and are thence conducted by a lateral pipe into a common distiller's worm, which, being surrounded by cold water, the vapours become condensed, and the resulting liquid, composed chiefly of water and alcohol, in the state of "low wines," is drawn off into suitable receptacles for subsequent rectification. In order to regulate the temperature of the oven, an iron tube, about the size of a musket barrel, and about a foot long, and closed at the lower end, is suspended vertically in the middle of the neck by passing it through a conical hole in the latter, to which it is closely fitted: in this tube oil is deposited, and into the oil is suspended the bulb of a thermometer, whose graduated scale above exhibits the temperature of the oil, and, consequently, very nearly that of the oven.
To equalize the application of heat to the oven, Mr. Hicks adopted the revolving fireplace of Steel and Brunton. For this purpose the oven is made circular, and at about a foot from the bottom of it is a large circular plate of the same diameter as the oven (six feet), which turns in a horizontal plane on a vertical axis, forming a complete partition between the fire-place and the ash-pit, except where the fire-grate is situated, which is made of a sectorial form, and, consequently, readily admits of being shifted into or out of its place; and, in order that the air which is admitted into the ash-pit to promote the combustion of the fuel may not be diverted from its proper course, the rim of the circular plate is provided with a descending rim, which dips into an annular channel filled with water, forming what is called an hydraulic joint. Mr. Hicks states in his specification, that when the thermometer before-mentioned indicated a temperature of 280° Fahr., the oven is at a proper heat for baking, and that, during the process, a heat from 280o to 310° should be maintained; and we know that at this temperature bread may be perfectly baked.
Notwithstanding this circumstance, we have proved, experimentally, that the heat of ordinary baker's ovens is usually not less than 800° Fahr. at the time the first bread is put in; but the rapidly cooling influences it is afterwards subjected to, probably renders such a high temperature necessary at the commencement of baking by the ordinary process; this apparently entails such a wasteful expenditure of fuel, that it is well deserving of investigation which of the two modes of baking, that of a great heat at the commencement only, or that of a moderate heat continued throughout the process, is the best. It has been held, that the latter has the advantage of rendering the bread sweeter, by the vapour carrying off matters that are both unsavoury and prejudicial; while the former, from the vapour being retained in the oven, infects the bread. But this opinion can have but a slight basis to rest upon; a little reflection will show us that in Hicks's oven, as in others of the same class, the vapour must pass off somehow, otherwise it would become dense, and acquire so much expansive force, at a temperature of 300°, as to burst open the oven.
The elasticity of the vapour in it, like that of a common still, can, therefore, but little exceed the pressure of the atmosphere; but this weak steam is highly heated by radiation from the top, sides, and bottom of the oven, and thus the baking is effected. Now, if we consider the mean heat of a common baker's oven to be 450° (and we know it is not less), it is quite obvious that dense steam at a such temperature could not exist in a structure of the kind; nor, indeed, at a heat much above 212°. And as 212° is much below a baking temperature, by far the greater part of the vapourized water must escape, in the form of steam, through some chinks or fissures in the brickwork or door; for if it did not, the density of the steam would, infallibly, soon blow open the oven. The baking is, in this case, as in the former, effected by means of weak steam, surcharged with heat, by radiation from the top of the oven, which must necessarily receive a higher temperature, because it has, from its arched form, to operate at a greater distance from the bread, and has to suffer a continual abstraction without any fresh supply; hence arises the question, whether the loss of caloric, radiating from the arched top of the common brick oven, is greater in amount than, that which escapes unused by continuous heating at a lower temperature.
There are, however, other considerations which should enter into the inquiry, which we have not space to pursue farther, but must proceed to the next subject that presents itself to our attention. This is a domestic oven, which, we are informed, has been brought successfully into use in several families. The annexed figure gives a sectional view, the front of the oven being supposed to be removed to show the interior construction, a is the oven; b b the flue, which passes over the exterior surfaces of the sides, the back, and bottom of the oven; c is the furnace; d the ash-pit; e the brick-work enclosing the oven. It is not intended that anything should be placed on the bottom of the oven. The shelves are not formed of iron plates, but consist each of two oblong trivets of wrought iron, placed side by side, a little distance apart from each other. The oven is supported at the back by horizontal bars fixed in the brickwork at each corner.
The front of the oven has three separate doors and frames; one larger one for the oven part, two smaller underneath for the furnace and the ash-pit.
Notwithstanding the commendation this oven has received, it appears to us to possess the common defect of the ordinary ovens attached to kitchen grates; that of communicating a scorching heat in one part of the bread, or other article, while the opposite side of it is comparatively cold. Skilful operators may, by turning the bread frequently, and carefully regulating the temperature, bake tolerably; but without some very active circulating intermedium, ordinary attention will not suffice to bake in a proper manner. How far these defects are obviated in a recent invention, denominated Hebert's Patent Domestic Oven, the reader will determine. The object of the inventor has been to provide a very cheap and durable apparatus, capable alike of baking bread properly, and cooking other kinds of food; they are made of various sizes, to adapt them to the wants of different individuals, and are rendered as portable as possible, to suit the requirements of the army and navy. We shall here add, by way of example, a description of the smallest size, which we saw in the warehouse of the agents, Messrs. Donaldson and Glasgow, of Birmingham.
Fig. 1 exhibits an external view of the whole apparatus; the outside vessel b being simply a well-made cast-iron boiler, or pot, which, when used alone,
(that is, without the internal apparatus described underneath,) is applicable to all the various uses of other boilers, - but it possesses this further advantage, of having a strong double cased iron lid c, ground to fit so closely as to prevent the radiation of heat, and the escape of the rarefied steam, while it easily permits dense elastic vapour to pass off. The vessel is to be suspended over or in front of a fire, and in the case of the larger sizes, they may be conveniently set in brickwork, after the manner of common boilers.
For the purpose of baking bread or pastry, the roasting of meat, steaming of potatoes and other vegetables, etc, there is placed inside the pot delineated in Fig. 1 a perforated vessel, shown in Fig. 2. This vessel is made of smooth cast-iron, and drilled with holes at the side and bottom; and by means of little prejecting studs, it is held steadily in the middle of the outer vessel, so as to leave a free space of about a quarter of an inch between both; around which space there is constant circulation of extremely hot vapour, which operates upon every part of the bread or other material placed therein. To receive the latter, there is a movable bottom, shown separately in the adjoining Fig. 3, which is removable at pleasure; but it serves to correct the tendency of too much heat in this part, when the oven is suspended over a strong fire.
it facilitates the discharge of the contents of the oven, and is easily kept perfectly clean.
Inside of Fig. 2 there is also placed occasionally a connected series of shelves, or pans dd, which may either consist of two, as represented in the annexed Fig. 4, or of a greater number in the larger sizes. These are for the purpose of baking small bread, rolls, biscuits, tarts, etc. - the roasting of potatoes, for frying or stewing meat, etc. - which may easily be withdrawn from the oven by means of the bail handle e, which is jointed so as to fall down on either side.
A fifth appendage, for roasting meat, is also supplied. It consists, as represented in Fig. 5, of a circular dripping panf, having an upright spit g in the centre, and a jointed bail handle for putting it in or taking it out of the oven. The pan serves equally well for broiling, frying, and other processes, which every cook will comprehend without explanation.
The patentee states, that, by the application of the several parts of this apparatus, either in their single state, or combined in the various ways explained, bread and all other kinds of food may be baked, roasted, boiled, stewed, or fried, with the utmost facility and economy; the instructions for which are sent out with each of the ovens.