The right sort of glue to use for ordinary work is “best Scotch” (inferior kinds are often adulterated with lime). This glue is sold at all good tool shops; but if it cannot be obtained, choose the most transparent cakes. For fine work in light-coloured woods, Salisbury glue may be used; this is made in thin cakes, and is of a clear amber colour.
Preparation of the glue. Break it into small pieces with the hammer, and soak for at least twelve hours in sufficient water to keep it covered even when swollen by the water it absorbs: this water must be cold. It is no use attempting to melt glue by putting it into hot water; it will always be stringy, and give endless trouble. Put the pieces of soaked glue without any superfluous water into the glue pot, taking care that the outer vessel is kept full of water, which will prevent the glue in the inner vessel from burning ; this is very important.
The glue will now soon dissolve; it will be thin at first, but quite strong enough; subsequent boilings will, however, improve it, so long as it is never allowed to burn; indeed, as water is driven off by evaporation, more will have to be added. If stronger glue is required, it may be made with beer instead of water, and stronger still, if linseed oil is added to it instead of water, as the original water in which it was dissolved is evaporated by boiling.
Cleanliness is very essential to the well-being of glue; a wooden cover should therefore be provided for the pot, and if any dust or dirt is on the cold glue, it should be just washed off before putting the pot on the fire. A scum always rises as the glue boils; carpenters generally stir this in with the brush, I prefer to skim it off, and put it in a gallipot, where it accumulates and settles with waste scrapings, and much of it may be utilised afterwards.
A wire stretched across the pot is very useful to remove superfluous glue from the brushes; this is much better than pressing them against the edge of the pot, where quite enough glue is sure to accumulate and burn. Never use any of that old dried up and burnt glue, which may be generally found in the bottom of a glue pot kept in a kitchen; have the whole concern boiled out in a saucepan, before you put your nice fresh clean glue into the pot.
How to use the glue. It must not be supposed that the strength of a glue-joint depends upon the quantity used; those joints hold the best in which the pieces of wood are brought closest together. The following is a brief description of the process to be pursued :—Have the glue as hot as possible, the glue pot within easy reach, a basin of hot water, and a bit of sponge on the bench. Cover quickly with hot glue both the surfaces to be united, and rub them together, pressing out all the glue that can be got rid of; let the motion of the one piece on the other be but slight; for instance, in a three foot joint the top piece need never have more than an inch or two beyond the other, which is fixed, it is supposed, in the bench screw; it will soon be felt that they are inclined to stick together, then they must be brought at once to that which is to be their final position, and not moved again.
Superfluous glue may now be wiped off with the sponge when necessary, as when it is in an angle or an awkward place to get at afterwards; but as a general rule, and particularly in a long joint, it should be left on till cold, for it excludes the air, and goes a long way towards making a good, permanent joint.
If the edges of two long boards have to be glued together, the job will require two hands. One board having been fixed in the bench-screw, the other is rested against it, so that the edges meet obliquely, making a very blunt V. While one workman steadies this second board (with the help of a weight, or the jack planes on the bench, to keep it from slipping), the other holding the glue pot in his left hand, passes the brush, well loaded with glue, rapidly along the edges; he must not mind wasting his glue, there is no time now to be careful about not spilling a drop or two. When the edges are quite covered, he takes one end of the loose board, his assistant the other, and they rub it up and down a time or two, till it sticks, as with shorter pieces.
And here note, that it you are not skilful enough to shoot a perfectly true edge on your board, make it slightly concave rather than convex; for the ends always have a tendency to rise. In glueing flat pieces of wood together, such as two or three thin pieces to make one thick, with the grain running different ways, screw-clamps are required: these are wonderfully useful things for many purposes, very cheap, and not half enough used by amateurs.
The softest woods should be chosen for veneering upon—such as common cedar or yellow-pine;—perhaps the best of all for the purpose is “arrow board,” twelve foot lengths of which can be had of perfectly straight grain, and without a knot; of course no one ever veneers over a knot. Hard wood can be veneered, boxwood with ivory, for instance ; but wood that will warp and twist, such as nasty crossgrained mahogany, must be avoided.
The veneer, and the wood on which it is to be laid, must both be carefully prepared, the former by taking out all marks of the saw on both sides with a fine toothing plane, the latter with a coarser toothing plane. If the veneer happen to be broken in doing this, it may be repaired at once with a bit of stiff paper glued upon it on the upper side.
The veneer should be cut rather larger than the surface to be covered; if much twisted, it may be damped and placed under a board and weight over night. This saves much trouble; but veneers are so cheap, about 1d. a foot, that it is not worth while taking much trouble about refractory pieces. The wood to be veneered must now be sized with thin glue; the ordinary glue pot will supply this by dipping the brush first into the glue, then into the boiling water in the outer vessel. This size must be allowed to dry before the veneer is laid.
We will suppose now that the veneering process is about to commence. The glue in good condition, and boiling hot, the bench cleared, a basin of hot water with the veneering hammer and a sponge in it, a cloth or two, and everything in such position that one will not interfere with, or be in the way of, another.
First, Damp with hot water that side of the veneer which is not to be glued, then glue the other side. Second, Glue over as quickly as possible the wood itself, previously toothed and sized. Third, Bring the veneer rapidly to it, pressing it down with the outspread hands, and taking care that the edges of the veneer overlap a little all round. Fourth, Grasp the veneering hammer close to the pane (shaking off the hot water from it) and the handle pointing away from you; wriggle it about, pressing down stoutly, and squeezing the glue from the centre out at the edges.
If it is a large piece of stuff which is to be veneered, the assistance of a hot flat iron from the kitchen will be wanted to make the glue liquid again after it has set; but don’t let it dry the wood underneath it, or it will burn the glue and scorch the veneer, and ruin the work. Fifth, Having got out all the glue possible, search the surface for blisters, which will be at once betrayed by the sound they give when tapped with the handle of the hammer; the hot iron (or the inner vessel of the glue pot itself, which often answers the purpose) must be applied, and the squeezing process with the hammer repeated. When the hammer is not in the hand, it should be in the hot water.
The whole may now be sponged over with hot water, and wiped as dry as can be. And observe, throughout the above process never have any slop and wet about the work that you can avoid. Whenever you use the sponge, squeeze it well first. Damp and heat is wanted, not wet and heat. It is a good thing to have the sponge in the left hand nearly all the time, ready to take up any moisture or squeezed-out glue from the front of the hammer.
So much for laying veneers with the hammer, which, though a valuable tool for an amateur, is not much used in the best cabinetmakers’ shops; cauls are adopted instead. They are made of wood, the shape and size of the surface to be veneered, or better still, of rolled zinc plate, and being made very hot before a good blaze of shavings, they are clamped down on the work when the veneer is got into its place: they must be previously soaped, to prevent them sticking to the veneer. The whole is then left to dry together.
The hammer is quite sufficient for most amateurs. I have laid veneers with it 5 feet long by 18 inches wide, without assistance, and without leaving a blister. Cauls, however, are very necessary if a double curved surface has to be veneered, or a concave surface; they need not be used for a simple convex surface. By wetting well one side of the veneer it will curl up, and can easily be laid on such a surface; but it will be well to bind the whole round with some soft string to assist it in keeping down while drying.
No attempt at scraping, sand-papering, or polishing veneered work must be made till the glue is perfectly dry and hard. It should be left twenty-four hours in a warm room at least, and better still if left two or three times as long.
The processes for French polishing vary somewhat according to the nature of the wood. For common work in deal, the wood may be well sized first, then papered with fine glass-paper, and polished.
For mahogany, walnut, and similar porous woods, the pores must be filled by rubbing in, on a roller of old carpet, a mixture of Russian tallow (that is, tallow free from salt) and plaster-of-Paris, well amalgamated—before the fire in cold weather. Russian tallow may be had at most oil shops generally pure enough; but if the presence of salt is suspected, refine it by boiling it in plenty of water, stirring it well, and skimming it. Set it by to cool, and use the cake of tallow which will be at the top.
The more this filling-up process is persevered in, the less will be the subsequent labour in polishing: quite a bright surface should be got up by this alone. The mixture of tallow and plaster may be darkened with red lead for mahogany, or other colouring matter, according to fancy. This filling is not necessary for boxwood, ebony, or others of the hard woods.
To polish a surface thus prepared, not being hard wood and not in the lathe, take a ball of cotton wool saturated with methylated French polish; cover it with a fold of linen cloth; on the linen cover put with the tip of the finger a drop or two of raw refined linseed oil (not “boiled oil”); get on a good body of varnish by rubbing always one way with circular strokes; be very careful to go over all the ground each time you work round the surface; and do not go over the same spot twice before you have gone over all. The longer this is done the better. Never mind the smears, which, though they look queer, are the very appearance you want at this stage. Having got on a good body, leave your work and take to another piece. It is good to leave it, if convenient, even for a day or two. By the way, shut all doors and windows before you begin. You can’t do French polishing in a draft or in a very cold room.
When you resume work, use a mixture of half methylated French polish, and half methylated spirit, or less than half of the spirit when you commence, and put now as little as possible on the wool, covering it with more than one fold of fine linen or cambric. Very little oil, as before—only just enough to prevent the rubber from sticking to the work; go over it lightly, with an easy gentle touch, in circular strokes, all one way.
Never mind the smears. When it comes to look something like a good result, which it soon will, you may take out the smears by rubbing up and down with a mere trace of spirit on wool well covered with the linen, but avoid going over the same place twice, and be very light and gentle, or you will remove your polish. Finally, rub it well with a clean wash leather (carefully folded, so as to have no hard crease which will scratch), or an old silk hand-kerchief, breathing on the work occasionally.
Boxwood, ebony, cocus, &c, may be rapidly polished in the lathe. At first get a body on of polish, and this can be done without using any oil. The work must not be turned round rapidly, but the pulley of the lathe moved slowly by hand ; then use your rubber with a drop of oil, and finally, the polish thinned with spirit.
If either on flat or turned work you require a very superior polish, you may remove nearly all the first coat with fine glass-paper, and put it on again, which will not take long, the pores being all filled. Remember that throughout the oil is only used to prevent the rubber from sticking, and it has to be got out afterwards with the spirit; so never use more than necessary.
In the lathe, when you come to the wash leathers, the work may be driven rapidly. A bit of ebony can be polished in five or six minutes to such a surface that small print can be easily read in it as in a mirror. Don’t use your rubbers when they get hard and dry, but nevertheless stick to an old one as long as you can, and if you have to put them by, keep them in a tin box tightly covered.
Sherrard B. Barnaby
The Quarterly Journal of the Amateur Mechanical Society – July, 1871