During the past few weeks, a highly interesting experiment--and one,
moreover, destined to materially influence the development of the uses
of gas in a fresh field--has been in progress, under the guidance of Mr.
Booer, at a baker's shop in the Blackfriars Road, London. The experiment
in question is nothing less than the application of gas for heating
bakers' ovens, in a manner not hitherto attempted, and such as to bring
the system within the means of the poorest tradesman in all but the
smallest towns. It will be remembered that the success of the gas-heated
muffles for burning tiles and glass led to the attempted construction of
a model baker's oven, heated by the same fuel, which was shown in action
at the Smoke Abatement Exhibition at South Kensington in the winter
of 1881-82. This model attained considerable success; but its design
demanded either a new structure in every case, or considerable
alteration of any existing oven. In the proposed system, moreover,
the oven was heated wholly from without--a condition supposed to be
necessary to meet the objections of the bakers. It is evident, however,
that there must be considerable waste of gas in heating a mass of tiles
and brickwork, such as go to the construction of a common baker's oven,
from the outside; and the objection to handicapping such a costly fuel
as gas in this manner becomes more apparent when it is remembered that
in the usual way the oven is always heated by an internal coal fire.
When it is further considered that the coal commonly used by bakers is
of the most ordinary quality, full of dirt that would condemn it in the
estimation of a gas manager, the sentimental objection to allowing a
purified gas flame to burn in a place which this rubbish is permitted to
fill with foul smoke becomes supremely ridiculous. Consequently, when
Mr. Booer, whose work in connection with the gas muffle is well known
in England and America, seriously addressed himself to construct, upon
altogether new lines, a cheap and practical baker's oven, he wisely put
the gas inside.
There are many other conditions which Mr. Booer, after consultation with
practical bakers and others, set himself to fulfill, the observance
of which lends to the present Blackfriars experiment much of its
interesting character. Thus it was observed that, while it is not
difficult to build an oven in a given spot, and bake bread in it, this
cannot truly be called a _baker's_ oven. By this term must be understood
in particular an oven in an ordinary bakehouse, set in the usual style
and worked by a man with his living to get by it. Before the problem of
extending gas to bakers' ovens could be considered solved, it had to be
attacked from this aspect. Mr. Booer, to do him full credit, seems to
have early appreciated this fact in all its bearings. He not only saw
that it was necessary to save gas, as much as possible, by putting it
inside the oven; but he was told that, in order to meet with any general
success, the cost of converting an oven to the gas system must be
rigidly kept down to about ten or twelve guineas. The latter seems
a particularly hard condition, when it is remembered that the only
improved baker's oven in practical use at the present day is the steam
oven invented by Mr. Perkins, which costs two or three hundred pounds to
erect. Mr. Booer also had in mind the necessity that everything possible
for a coal oven must likewise be performed by a gas oven; and in this
respect he set himself to surpass the costly Perkins oven, which will
not bake the common "batch" or household bread, generally the principal
article of sale, more especially in populous and poor neighborhoods. The
peculiar efficacy of the common coal fire in this respect proceeds from
the essential principle of action of a brick oven, which is found simply
in the fact that the work is done entirely by heat previously imparted
to the tile bottom, roof, and sides of the oven, and thence radiated to
the bread. No other kind of heat will bake batch-bread--i.e., loaves
packed in contact with one another--which requires to be thoroughly
soaked by a radiant heat in a close atmosphere of its own steam. Now,
as a coal fire is eminently qualified to impart, by radiation and
otherwise, this necessary store of heat to the brickwork, it is plainly
a difficulty to effect the same purpose with a fuel which, of
itself, can scarcely radiate heat at all. The system of the gas
cooking-oven--the utilization of the heat of the combustion products as
formed--is clearly inapplicable here; for a different kind of heat is
needed, under conditions that would not sustain continuous combustion.
Therefore, there is nothing for it but to heat the bottom and sides
of the brick oven by the direct contact of powerful gas-flames; thus
supplanting the coal fire, but leaving the actual work of baking to be
done afterward by stored-up heat in the regular way.
Having settled the general principles of a system of this kind, there
still remain a number of scarcely less important details, in the dealing
with which lies the difference between practical success and failure.
Thus it is not merely sufficient to heat an oven for bread baking; it is
also necessary to heat it within the times and according to the habits
of work to which the baker has been accustomed. Work in town bakeries
begins at about midnight, or shortly after, and the condition of the
oven must conform to the requirements of the dough, which vary from day
to day and from season to season. In order to master all these niceties,
as far as a knowledge of them is necessary to his purpose, Mr. Booer
has spent many nights in the bakehouse in the Blackfriars Road; and has
thereby obtained a command over the technicalities of the work which has
served him in good stead, not merely for adjusting his gas heat, but in
answering the innumerable objections always raised when a revolution in
an immemorial trade is threatened. It is with considerable satisfaction
that we are enabled to declare, after duly weighing all the conditions
as to first cost and otherwise imposed by himself and others, that Mr.
Booer has succeeded, upon these terms, in vindicating the claims of gas
to be a cheap, efficient, and cleanly fuel for heating ovens under the
control and according to the methods of working of the baker himself.
The oven with which this success has been achieved is one of two in the
bakehouse of Mr. Loeber, of 161 Blackfriars Road. It measures 7 feet by
6 feet internally; being what is technically termed a 6 bushel oven. The
alterations made by Mr. Booer consist in the first place in the removal
of the flooring tiles, and the laying down of a new bottom, under which
run a number of flues radiating from the side furnace. The throat of the
furnace, where it enters the angle of the oven, is bricked up, and eight
pieces of ¾-inch gun-barrel tubing project above this dwarf wall,
and radiate fan-shaped under the dome of the roof. These are the
gas-burners, which are supplied from a 1½-inch pipe led into the old
furnace. The same pipe supplies the similar burners which are inserted
in the flues under the oven bottom. This is really all the plant
required. It should be remarked that these bottom flues are carried to
different points of the side walls, and the products of combustion are
allowed to rise upward into the oven through gaps left for the purpose.
A supplementary supply of heated air is provided to help the combustion
of the gas in these flues, which would otherwise be languid. When the
gas is turned on from the main cock in the furnace either to the top or
the bottom set of burners, a long match is used to light them from
the same point. This is effected without risk of firing back, by the
adoption of a specially constructed atmospheric nipple and shield, the
pattern of which is registered. The flame from the top burners unites in
a sheet of fire, which spreads out all over the crown of the oven, at
the same time that the burners below are doing their work, and the
products of combustion flow together through the oven to the chimney,
which is the same that was used for coal. At first, as might be
expected, there was considerable difficulty in finding the most suitable
position of the chimney damper, aggravated in this case by the fact that
the other oven worked with a coal fire into the same shaft. Finally,
however, the two flues were disconnected with the happiest results.
During the past fortnight the oven has been in regular use, and the
bread has been sold over the counter in the ordinary course of trade.
Two and three batches of bread have been baked in one day in this oven;
the economy of its use, of course, increasing with the number of loaves
turned out. As a rule the gas is lighted for about an hour before the
oven is wanted, and about 250 cubic feet are used. Then the cocks are
shut and the oven is allowed to stand closed up for ten minutes, in
which time it ventilates itself, and the heat spreads over it. Then the
batch is set, and the baking occupies from an hour to an hour and a
half, according to the different classes of loaves. Two batches are
baked with a consumption of about 620 cubic feet of gas; costing, at 2s.
10d. per 1000 cubic feet, just 11d. each batch for fuel. This cannot be
considered costly. But the system possesses many other advantages. In
the first place, it is much more cleanly than coal; for the oven never
requires wiping out, which is usually done with a bundle of old rope
called a "scuffle" and the operation is attended with a most unpleasant
odor. Then there is no smoke--a great advantage from the point of
view of the Smoke Abatement Institution. More to the purpose of the
journeyman baker, however, is the fact that there is no stoking to be
done, and he can therefore take his repose at night without having to
attend to the furnace. Besides this the master has the satisfaction of
knowing that the oven will always be hot enough if he simply attends to
the time of lighting the gas--a consideration of no small moment. It is
no mean testimony to the reality of Mr. Booer's success that Mr. Loeber,
having seen his difficulties and troubles from the beginning, and marked
how they have been overcome, is content to acknowledge that even this
first example is capable of turning out bread in a condition to be sold
over the counter. There is a good opening in this direction, for there
are 6,000 bakeries in London alone, to every one of which Mr. Booer's
system might be applied with advantage to the tradesman and his
customers. And what may be done with gas at about 3s. per 1,000 cubic
feet may certainly be done to still greater advantage in many towns
where the price is lower. Mr. Booer has entered upon his work in a
proper spirit. He has begun at the beginning, with the necessities of
the baker; and has gone plodding on quietly, until he has achieved a
noteworthy success. It may be hoped he will receive the reward which his
perseverance merits.--_Jour. of Gas Lighting_.
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