The Chemistry of Cookery

by W. Mattieu Williams

But why are these roasters not in general use? Why did they die with their inventor, notwithstanding the fact, mentioned in his essay, that Mr. Hopkins, of Greek Street, Soho, had sold above 200, and others were making them?

Those of my readers who have had practical experience in using hot air or in superheating steam, will doubtless have already detected a weak point in the ‘blowpipes.’ When iron pipes are heated to redness, or thereabouts, and a blast of air or steam passes through them, they work admirably for a while, but presently the pipe gives way, for iron is a combustible substance, and burns slowly when heated and supplied with abundant oxygen, either by means of air or water; the latter being decomposed, its hydrogen set free, while its oxygen combines with the iron, and reduces it to friable oxide. Rumford does not appear to have understood this, or he would have made his blowpipes of fire-clay or other refractory non-oxidisable material.

The records of the Great Seal Office contain specifications of hundreds of ingenious inventions that have failed most vexatiously from this defect; and I could tell of joint-stock companies that have been ‘floated’ to carry out inventions involving the use of heated air or super-heated steam that have worked beautifully and with apparent economy while the shares were in the market, and then collapsed just when the calls were paid up, the cost of renewal of superheaters and hot-air chambers having worse than annulled the economy of working fuel described in the prospectus. Thus a vessel driven by heated air, as a substitute for steam, was fitted up with its caloric engine, and crossed the Atlantic with passengers on board. The voyage practically demonstrated a great saving of coal; the patent rights were purchased accordingly for a very large amount, and shares went up buoyantly until the oxidation of the great air chamber proved that the engine burned iron as well as coal at a ruinous cost.

Although no mention is made by Rumford of such destruction of the blowpipes, he was evidently conscious of the costliness of his original roaster, as he describes another which may be economically substituted for it. This has an air chamber formed by bringing down the body of the oven so as to enclose the space occupied by the blowpipes shown in [Fig. 1], and placing the dripping-pan on a false bottom joined to the front face of the roaster just below the door, but not extending quite to the back. An adjustable register door opens at the front into this air chamber, and when this is opened the air passes along from front to back under the false bottom, and rises behind to an outlet pipe like that shown at v, [Fig. 1]. In thus passing along the hot bottom of the oven the air is heated, but not so greatly as by the blowpipes, which being surrounded by the flame on all sides, are heated above as well as below, and the air in passing through them is much more exposed to heat than in passing through the air-chamber.

To increase the heat transmitted in the latter, Rumford proposes that ‘a certain quantity of iron wire, in loose coils, or of iron turnings, be put into the air chamber.’

This modification he called a ‘roasting-oven,’ to distinguish it from the first described, the ‘roaster.’ He states that the roasting-oven is not quite so effective as the roaster, but from its greater cheapness may be largely used. This anticipation has been realised. The modern ‘kitchener,’ which in so many forms is gradually and steadily supplanting the ancient open range, is an apparatus in which roasting in the open air before a fire is superseded by roasting in a closed chamber or roasting-oven. Having made three removals within the last twelve years, each preceded by a tedious amount of house-hunting, I have seen a great many kitchens of newly-built houses, and find that about 90 per cent. of these have closed kitcheners, and only about 10 per cent. are fitted with open ranges of the old pattern. Bottle-jacks, like smoke-jacks and spits, are gradually falling into disuse.

When these kitcheners were first introduced, a great point was made by the manufacturer of the distinction between the roasting and the baking-oven; the first being provided with a special apparatus for effecting ventilation by devices more or less resembling that in Rumford’s roasting-oven. Gradually these degenerated into mere shams, and now in the best kitcheners even a pretence to ventilation is abandoned. Having reasoned out my own theory of the conditions demanded for perfect roasting some time ago (about 1860, when I lectured on ‘Household Philosophy,’ to a class of ladies at the Birmingham and Midland Institute), I have watched the gradual disappearance of these concessions to popular prejudice with some interest, as they show how practical experience has confirmed my theory, which, as already expounded, is that fresh meat should be cooked by the action of radiant heat, projected towards it from all sides, while it is immersed in an atmosphere nearly saturated with its own vapours.

Let it be clearly understood that I refer to the vapours as they rise from the meat, and not to the vapour of burnt dripping, which Rumford describes. The acrid properties of the products of such partial dissociation are far better understood by modern chemists than they were in Rumford’s time.

His water dripping-pan effectually prevents their formation. It is still manufactured of the precise pattern shown in the drawing, copied from Rumford’s, and cooks who understand their business at all use it as a matter of course.