The Useful Arts Employed in the Construction of Dwelling Houses. Second Edition

by Anonymous

Supposing the top of a sideboard to be the article which is to be veneered. The workman cuts out a piece of veneer, a little larger than is actually required, to allow for waste; and then lays it flat on his work-bench. With a veneering plane—which is a small-sized plane, having an iron jagged with notches like the teeth of a very fine saw—he works steadily over the whole surface of the veneer, carrying the plane in the direction of the grain of the wood. The action of this plane-iron removes all the saw marks, which were irregular in their course, and gives instead of them a series of regular parallel channels from end to end of the piece of veneer; these channels are but small in depth, and their object is to retain the glue which is afterwards used in the process of veneering.

The surface of the deal or other wood on which the veneer is to be laid, is in like manner planed with these parallel indentations; and then the process of veneering proceeds. The wood, having been well warmed before a fire, is coated with warm melted glue; and the piece of veneer is laid down flat on the veneered surface, and rubbed backwards and forwards, in order that the glue which is between the veneer and the under-wood may be pressed into all the little grooves produced by the plane. When the glue begins to get cool, the veneer can no longer be pressed to and fro, and is then left. This glueing has the general effect of making the veneer adhere to the foundation beneath; but there are parts where, from the accumulation of too much glue in one part, or from the presence of air which had not been expelled by the pressure of the hands, the veneer rises up as a kind of blister, convex on the upper surface. The workman employs a veneering hammer to level these protuberances. This veneering hammer is a piece of wood three or four inches long, and an inch in thickness, having a straight strip of iron plate fixed to one edge. The workman, placing the iron edge down upon the veneer, presses on the block of wood with his hand, and works all over the surface of the veneer, expressing all the superfluous glue from the parts which had formed the protuberances. As this redundant glue must have some place from whence to escape, the workman begins rubbing at the centre, and thence proceeds towards the edge, at which the glue finally exudes. There is a curious plan adopted for ascertaining whether there are any parts, imperceptible to the eye, where the veneer does not adhere closely to the foundation—viz., by sound. The workman strikes the veneer all over with a wooden or other hammer; and if the sound be distinct and solid, he knows that the proper degree of adhesion has taken place; but if the sound be hollow and dull, it indicates the existence of a vacant space between the veneer and the foundation; and a greater degree of rubbing or pressing is consequently necessary. If the surface of the piece of veneer be of large dimensions, two workmen are required to level all parts of the veneer before the glue gets cold and loses its fluidity.

But this operation—however good the glue may be, or however well the veneer may be pressed down—is not sufficient to cause the veneer to adhere permanently to the foundation, especially at the edges, where the air is liable to enter, and to cause the veneer to rise. To prevent this inconvenience, the veneer, at and near the edges, is kept down, either by the pressure of heavy weights, or, still better, by the action of screw-presses. These screw-presses consist of two pieces of wood or clamps, which are brought to any degree of closeness by means of two wooden screws, each screw passing through holes in both clamps, the handles of the two screws being, respectively to each other, outside the opposite clamps. The clamps are opened, by means of the screws, to such a width as to admit the edge of the veneered wood between them; and the screws are then worked up till the clamps grasp the wood tightly, where they remain till the glue is quite cold, and the veneer closely adhering to the foundation.

But even all this care is not in every case sufficient to produce a firm adhesion of the veneer to the foundation. It frequently happens that, when the hardened veneered surface is tried with the hammer, a hollow sound indicates that there is yet a place where the veneer has a vacancy beneath it. In such a case, the only remedy is one of a curious kind—viz., to lay a hot iron on the defective part of the veneer, by which the glue beneath is remelted. A small part of the veneer, reaching from the defective part to the edge, is also similarly heated, and the glue beneath remelted. Then, by means of the veneering hammer, the superfluous glue which had caused the defect is squeezed out, and pressed to the edges of the veneer through the kind of channel which had been prepared for it by the heated iron.

Where the surface of the wood to be veneered is more or less cylindrical, such as a pillar, the front of a drawer, &c., the piece of veneer has a curvature given to it, corresponding in some degree to that of the surface on which it is laid, by the action of hot water, before the glueing is effected. By sponging one side of the veneer with hot water, it causes that side to swell, while the other side remains dry; the consequence of which is, that the wetted surface rises into a convex form, leaving the other side hollow or concave:—this is, in fact, an instance of warping, where a thin piece of wood is either unequally heated or damped on opposite sides. The hollow side is then laid on the glued foundation.

When the veneered surface is dry, its edges are trimmed, and its surface scraped and sand-papered, preparatory to the finishing processes which the piece of furniture is to undergo.

Manufacture of Glue.

The preparation of this useful article forms a curious and important branch of national industry. The chief use of glue is for binding or cementing pieces of wood together, as practised by the carpenter and cabinet-maker, in which trades very large quantities are constantly employed.

Glue (which is nothing more than gelatine in a dry state) is obtained from the hides, hoofs, and horns of animals; the refuse of the leather-dresser, and the offal of the slaughter-house; ears of oxen, calves, sheep; parings of parchment, old gloves; and, in short, animal skin and (by a late improvement) bones, are all employed for making glue.

The first process in this manufacture is to free the materials from dirt, blood, and other matters which do not afford glue. For this purpose they are steeped in lime and water, and then placed in baskets, and rinsed by the action of a stream of water. They are then removed to a sloping surface, and allowed to drain, and whatever lime remains is deprived of its caustic property by the reabsorption of carbonic acid from the atmosphere, since the presence of lime would prove injurious in the subsequent processes.