TO REPAIR WOOD-CARVING—GLUE—NITRIC ACID GLUE—PREPARING DECAYED WOOD—ARTIFICIAL WOOD—FILLERS—SPRAYING—TO MAKE GLUE “TAKE.”

It will sometimes happen to a carver that, owing to bad wood or inadvertence, he splits away or breaks off a piece from his work. In this case he must have recourse to glue. This should be of the very best quality, perfectly light and clean. Glue is made in what alchemists used to call a balneum mariÆ, that is, of a vessel containing hot water, within which is a smaller vessel. The glue, which is in the inner pot, is therefore to be boiled by the heat of warm water, and not of the fire directly. Before setting it to boil, break it into very small pieces, say of the size of a hazel nut, and let it stand in cold water for twelve hours. It will now be like a thick jelly. Pour off all the water not absorbed, and put the jelly into the inner pot, fill the outer with water and let it boil till the glue is like a thick cream. Use it while in this state.

If you add to the glue, while thus liquid, some nitric acid, say about a tea-spoonful to half a pint of glue, you will have a very superior cement, which holds faster than the plain glue, and is much less liable to crack or split. It dries more slowly, which makes it very valuable for veneering and for large surfaces, where glue often dries before the whole can be applied. Again, when an article fastened with common glue is detached, it is often almost impossible to stick it on again with the same. But with the acidulated glue this is easy.

The greatest advantage of this glue is, that if it be kept excluded from the air it will remain in a liquid state for at least a year, and can be used cold. Its disadvantages are a very pungent and not agreeable smell, and the fact that, when corked up, the cork is most certain to get glued to the bottle, and requires to be broken to get it out, rendering a new one necessary. This may be avoided, however, with great care. Stir the acid into the glue with a glass rod or tube.

It may happen that a rotten, broken place is found even in the best wood; or the carver may obtain possession of a piece of ancient, worm-eaten, half-decayed carving, and with a very little skill such pieces can be perfectly repaired. Take a piece of similar wood, and reduce it to fine sawdust by means of a rasp. For this purpose American walnut and dark old oak, or cocoa-nut shell, which is easily pulverized in a mortar, is excellent. Make this into a paste with glue, and repair with it any broken places. This, if properly made, is quite like wood itself, and may be moulded into any shape. It “takes hold” of the ground, and when dry it may be filed into uniformity with the rest. It may also be cut with ease or trimmed to shape, or, in fact, carved. If there is too little glue in it it will break too easily, if there is too much it will be too glazy. But a proper mixture makes it quite like wood.

Scratches and chance cuts may be remedied by merely melting them with hot water. But for such small defects a filler is useful. This is a kind of paint or liquid cement, the object of which is to fill up the pores of certain coarse woods and make the surface fine. The squeezing wax, described in the chapter on making moulds, is a filler. Others are made by mixing flour with varnish, etc. Any dealer in paints and varnishes will supply a filler suitable to any special work.

When a piece of wood-work is so decayed that it is absolutely dropping to pieces, and cannot even be handled, it may be preserved and rehabilitated by the following process. Take some thin glue and water, or mucilage, or size of any kind, and a spray, that is, one of those articles such as are used for spraying perfumes, etc., and which are for sale in most chemist’s shops. Spray or sprinkle the glue over the figure, and, if necessary, gradually throw on it fine sawdust or other powder. As it dries it may be shaped and worked more freely.

We read continually in the newspapers of the opening of old tombs and ancient subterranean caves, in which are discovered dead bodies, bones, dresses, implements of bone and wood or leather, or even of baked earth, which gradually dropped into dust a few hours after being exposed to the air. And I have never known a case in which these objects could not have been preserved; certainly all which I have ever seen could have been. All that is necessary to do is to make a thin size, and very gradually spraying or sprinkling it on the objects, allow it to dry, little by little. There are very few cases in which, indeed, the spray cannot be successfully used. It was by the application of this principle that Sir Joseph Hooker preserved the ivory articles brought from Nineveh by Sir Austen H. Layard, and which would have perished but for him. He advised that they should be boiled in gelatine. The student who becomes an expert in such repairing will find plenty to do, and it will be his own fault if it is not profitable. Nineteen people out of twenty have not the least conception of the degree to which repairs may be carried. Some years ago a gentleman in America had a very curious and valuable vase from the pyramid of Cholula in Mexico. It was very fragile, being made of the weakest terra-cotta, and having been broken to pieces, the owner was about to throw it away, but gave it to me. Some months after I repaired it so perfectly that the closest observation could not detect a flaw in it. I did this by fastening pieces of paper on the inside with gum, and so gradually bringing the fragments together, edge to edge, and fastening them with the acidulated glue. When all were together, there was, of course, a lining of paper. Where there was a fault or a deficiency outside, I filled it in with plaster of Paris, rubbed it all even, and coloured by “rubbing in” paint. This process would have been much easier with decayed wood.

In gluing ordinary wood together, heat the two pieces first. This renders them more inclined to “take” the glue. Sometimes it is a difficult thing to hold them together till they “set,” that is, adhere so firmly that they will hold. For this the clamp, Fig. 7a, may often be used. In other cases, take two pieces of wood, put one on each side of the parts to be glued, and tie them tightly together; sometimes clamps may be used to connect the binding pieces, when they are not applicable to what is to be glued. Strong indiarubber rings or gummed paper strips may be used in some cases. But with thought, ingenuity can generally be awakened so as to help one out of any such difficulty.

A very perfect resemblance to carved wood may be made by taking cocoa-nut powder or fine sawdust and mixing it with the acidulated glue, so as to make a paste as already described. Then, having ready a mould, either of plaster of Paris or of sunk or incised wood, and oiling it, take the impression. These casts, retouched and glass-papered, are quite like wood, and they may be used for decoration in doors.

The following are also excellent recipes for glue.

Liquid glue. Take of best glue three parts, place them in eight parts of water, allow them to soak for some hours. Take half a part of hydrochloric acid (muriatic acid), three-quarters of a part of sulphate of zinc, add to these the glue, and keep the whole at a moderately high temperature till fluid.

Exceedingly strong cement for glass and china. Take gum arabic and dissolve it in acetic acid instead of water. It must be melted in a hottish place; it will be much stronger if this be done. The finest quality of sheet gelatine makes a transparent glue.