CHAPTER XVIII 
METAL INLAYING 
Piercing the recesses—Punching them—Chiselling them—Engraving-Etching—Etching grounds—Transferring design—Needling—Mordants—Fusing the inlay—Depositing it—Hammering it in—A Japanese method. 

The practice of inlaying metal plates or lines into another plate of different colour is one of considerable antiquity. Beautiful specimens of the craft have come down to us from the Mycenaean age of ancient Greece, circa 1400­1000 b.c. And to-day the Japanese craftsmen show us how valuable these little touches of colour can be made. In this respect and in the production of patina European craftsmen have much tolearn from the East, and particularly from Japan. The all-over, brilliant polish of the average production of the silversmith is not the last word which can be said on the subject. Except in the case of table ware, the obvious cleanliness and brightness of which would seem to be desirable, the use of coloured inlays or patina could be largely adopted. 

One of the simplest methods of inlaying is that on which the pattern is drawn on a piece of sheet metal and cut out with the piercing-saw. Pieces of the metal which is to form the inlay are sawn to fit the openings, and afterwards soldered in to fill them. The whole work is then polished. If the two pieces of metal which are to form background and pattern are clamped together, the ornament may be sawn out at the same time and by the same cut which pierces out the opening to receive it. But you must allow for the width of the saw cut, for this would leave a little space all round the pattern to be filled up with solder. The best plan is to have the metal which is to form the inlay 
rather thicker and softer than the background, so that when it is put in place it may be hammered a little and stretched to entirely fill the opening. 

Parquetry inlays can be made in the same manner as those in wood. A number of narrow strips of the different metals employed are laid edge to edge and soldered together, Fig. 259. The compound strip is then sawn, at an angle to its length (sometimes 90°, but often less) into a number of strips, each the width of the required fillet. The ends of the strips are joined and the edges filed true. You have now a long fillet made up of alternate bands of the different metals employed, Fig. 260. 

If two or more wires composed of different metals are twisted together, annealed, drawn a few times through a square drawplate and then flattened by passing them through the rolls, they may be used as a fillet for inlaying, and will look not very different from one made in the manner described above. 

Inlays which do not go right through the metal into which they are fastened, must have the lines and spaces to receive them prepared in one of the following ways. The recesses may be (1) left at the time when the work is cast, stamped or electrotyped, or (2) cut, chiselled or punched out, or (3) etched out by acids or other mordants. Patterns and lines to receive inlays may be produced by means of chasing and repousse tools. For instance, with the tracer described on page 125, a narrow groove may be produced in the surface of a piece of metal. The line is then gone over again with a narrow, parallel-sided chisel with flat bottom. The groove made in this way will be square at the bottom, and it will have a little bank or ridge, formed from the metal driven outwards by the tools, on either side. These ridges are tapped down and form overhanging sides to the groove. The wire which is to form the inlay is now thoroughly annealed, laid in the groove and hammered home. The surface of the work is scraped and polished. 

The metal to be inlaid, if thick, can be supported on a solid stone or metal base, or it may be fixed on pitch while the groove is being prepared. Thin metal may be sup ported in the same manner; but the pitch should be allowed to get quite cold before the work is commenced; for if the pitch is soft, the background near the line traced will be depressed by the hammering, and will require to be tapped back afterwards. The forms of leaves, rosettes and other ornamental patterns may be stamped into the metal with suitably shaped punches, or spaces of any form " punched down " with ordinary repousse tools. Letters and numbers may be worked with the ordinary letter or number punches. A metal straight-edge clamped down on to the work, or a suitably shaped paper pattern, gummed down, will serve as a guide in setting out the letters—the side of the punch resting against the rule or paper. 

But to cut out the recesses with hammer and chisel, or by means of graver and scorpers is the more usual method. A heavy piece of work such as a brass inscription or memorial tablet, is supported on a solid base of stone or iron. To this a ledge projecting half an inch above the surface of the slab makes a good stop, it keeps the work from sliding about under the influence of the hammering. The chisels used are of various kinds. Some are graver-shaped, Figs. 261, 262, for outlining the pattern; and others flat-faced, and perhaps T3ff inch wide, for chipping away the material, Fig. 264. They are made about 6 inches long. The letters or design may be traced on to the metal with carbon paper, and then inked in—drawings made thus show up clearly. The chisel for outlining is triangular or lozenge-shaped at the point, Fig. 261. To sharpen it, lay one of the lower sides flat on the stone. Then lift the hand a little and rub until you have produced a facet on the tool. Do the same on the other side of the tool. The side view of the point is shown in Fig. 262. The ridge separating the two facets just made must be in line with the ridge which separates the two under-sides of the tool. The little angle or corner where the two facets meet the under-sides of the tool is very valuable in practice, for the tool slides along on it as the point cuts its way. Next rub down the back of the tool, B, keeping to the original angle. The sharpness of the point may be tested by touching it with the thumb nail. It should stick at once without slipping. If a wide line is required, the graver may be made to cut it by sharpening the tool on the under-side or belly, grinding away the lowest angle of the diamond for perhaps a quarter of an inch along the ridge. A tool so sharpened is called a lozenge scolloper, Fig. 263. But scollopers or chisels with parallel sides are made also; they are sharpened on front and back, and are made in several different widths. 

For the smaller work done b}^ engravers, the hammer is not required. The tools used have a small round handle, held in the palm against the ball of the little finger. They are known in this case as the graver or " burin," and scorpers. The latter are made in various shapes—flat, round, knife-edged, etc., see page 68. Engravers hold their work in various ways, much depending on its shape. 
(1) On a sandbag. This is a round pad of sheepskin, crammed very tightly with sand or whiting, or a mixture of whiting and plaster of Paris. This is better than sand, for there would be no danger of scratching the work should any of the contents escape. The work is held by the left hand on top of the bag, and turned about as required. 
(2) In a chuck or clam, Fig. 265.
 (3) On a pitch bowl (see Chapter XXVIII, page 252).
 (4) On a cement stick. 
(5) On a triblet or ring stick, Fig. 270. 

The designis drawn on the metal as described on page 243. The work being then held firmly, the engraver either out lines the pattern with the graver and afterwards removes the ground with scorpers, or cuts the ground away at once without troubling to outline it. The point of the graver should be pushed along just below the surface of the metal, firmly and without jerks. Or, the work may be turned or pushed against the point of the graver, while it is held more or less still. A deep line is cut by going over the same ground a second time. The graver may be made to cut a line of varying width. To do this it is only necessary to rotate the tool on its axis a little. The graver being diamond-shaped in section, this rotation brings part of one of the sides rather than only a corner into contact with the metal, and a wider cut is the result. If a flat scorper is rotated quickly from side to side and at the same time pushed forward, it will make a curious " wriggled " or zigzag cut, Fig. 266. This is a quick way of removing the ground, and it leaves the surface of the metal very rough. This is an advantage in some processes of inlaying—when a " well-keyed " ground is required. 

The third method by which recesses for inlaying may be prepared, is that of etching. Gold, silver, copper, brass, bronze, iron or steel, may be treated by this process. The work is first covered with a specially prepared wax or varnish " ground," and the design drawn on it with a steel point or " needle." The ground is in this way scratched through wherever the lines which form the design or pattern come, and the metal exposed. Some acid is then poured over it. The acid attacks the metal wherever it is not protected by the varnish and eats or bites a furrow wherever the needle has gone. The depth to which the lines are " bitten " depends a good deal on the strength of the acid solution, and on the time the work remains in the "bath," for the longer a line is exposed to the action of the acid the deeper and wider is it bitten. It will be seen then that a design may be etched in lines of varying thick ness, for it is only necessary to " stop out," i. e. cover up with varnish, any lines which are sufficiently bitten, and then to put the plate into the bath again till the remaining lines are finished. Or, the deep lines may be drawn and etched first and the faint ones drawn in afterwards and bitten only for a minute or two. The length of time required to etch the pattern may be but a few minutes, or it may be an hour or two. 


Rhind's is perhaps the best-known etching ground. It may be purchased from all dealers in etching materials. Another good etching ground (Bosse's), very widely used, is 
made as follows :— 
White wax 10 parts 
Gum mastic 6 ,, 
Asphaltum 3 ,, 

Melt the wax first in an oven. Stir in the other two. The ingredients must be very thoroughly mixed. The stirring must be continued long after any streakiness in the mixture has disappeared. This ground is quite black, though a thin layer of it is semi-transparent. If the asphaltum is left out the ground is quite transparent, but not quite so strong. 


Another ground is made of:— 
Yellow beeswax 2 parts 
Asphaltum 2 „ 
Burgundy pitch 1 „ 
Mix as above described. 

When cool roll the ground into balls about 1 1/2 inch in diameter. For use, a ball of ground is tied up in a double thickness of thin silk, blue-bag fashion. Beeswax, paraffin-wax, or shellac, dissolved in alcohol or chloroform mayalso be used for a ground, or for stopping out any part of the workwhich has beenbitten deeply enough. Rememberthat lines get wider the longer they remain in the acid. 

To ground a plate or other piece of work. Clean it thoroughly. Then heat it until it is rather too warm to hold. It may be held in a hand-vice over a gas-or spirit-flame, or laid on a piece of sheet iron and the heat applied below. When quite uncomfortably warm to the touch lay the plate on a table and dab or rub the ground all over its face. To spread the ground evenly it is usual to either roll a rubber squeegee in every direction over the surface of the plate, or to use a dabber, Fig. 267. This is made of horsehair silk or kid. The edges of the silk or kid are brought over a disc of cardboard and bound together with string in the centre of the disc, above, to form a handle. The dabber is patted over the work until the ground is spread quite evenly. It may be necessary to reheat the plate before this can be effected. The ground having been spread evenly over the plate, its surface is now blackened by moving it about a few inches above a bundle of lighted tapers. These give off a good deal of smoke and soon darken the ground. When cool its surface should have a quite smooth, blackened, half-polished appearance, and lines scratched by the needle should show up brightly in contrast. Work which by reason of its shape cannot be grounded in this manner, may be dipped into a vessel containing some of the etching ground, melted; or, the ground may be dissolved in oil of lavender or chloroform and painted over the work. It is well to remember that the whole of the work except the scratched-in design must be protected from the action of the acid, so the under-side and edges must be protected as well as the face. The old copper-plate etchers, however, used to make a little wall of wax round the edge of the plate which was to be bitten, thus turning the plate itself, with its wax rim, into a kind of trough, into which the acid could be poured. The back of the plate did not then require protecting. 

Designs may be transferred to the etching ground in the following way: Take a thin sheet of paper and go all over it with a soft black-lead pencil. Use the side of the point of the pencil, for it will make a broader mark. Cover the paper with close lines in several directions, till it has a grey, shiny surface all over. Lay this side of the paper on the etching ground, and put the paper on which your drawing is, above. Then go over all the lines of the draw ing with a fine point, pressing firmly, but not hard enough to penetrate the paper. The black lead from the lower sheet of paper will be transferred all along the lines to the wax ground, and show up in contrast with its blackened surface. If you have an etching press, it is only necessary to put your lead-pencil drawing, or a tracing of it, face downwards on the ground and pass work and drawing together through the press. The drawing will be reversed in the process, and care must therefore be taken with lettering. 


The needle used to scratch through the ground is just a pointed piece of steel. An ordinary sewing-needle set in a handle does very well. For broad spaces in the design, a chisel-shaped tool may be used instead. Or, a number of lines drawn so closely together that the acid may work its way from one to the other. A low wooden bridge laid over, but not touching the plate, forms a convenient rest for the hand. When the design has been gone over with the needle the plate is ready for biting. But first see that every part of the metal, except the scratched-in design, is protected from the action of the acid. Paraffin wax or Brunswick black may be used to cover any exposed parts. 

The acids or mordants used for the different metals are given below. They should be got ready at least an hour before they are wanted;—the ingredients taking some time to mix properly,—but then, in glass-stoppered bottles they will keep for months. 
Mordant for gold—• 
Hydrochloric acid 8 parts 
Nitric acid 4 ,, 
Perchloride of iron 1 ,, 
Water 40 to 50 parts 

For silver— Nitric acid 1 part Water 3 or 4 parts 
For copper, brass, etc.— Nitric acid 1 part Water 1 „ 
Sir Frank Short, R.A., the well-known etcher, gives the following mordants for copper plates— 
Nitric acid 1 part Water 
1„ 
Or— 
Nitric acid 1 part Water 2 parts Or— 
Dutch mordant—• 
Chlorate of Potash 2 parts 
Hydrochloric acid 10 „ 
Water 88 „ 
Or perchloride of iron. This bath consists of a 40% Baume solution of perchloride of iron in water. The Dutch mordant is much slower in its action than the others, and the line bitten by it does not spread so much 
in width. Mordant for iron or steel—  
Hydrochloric acid Water  2 parts 1 „  
In  mixing  these  solutions  remember  that  the  acids  should be poured into the water, not the water into the 
acids. 

Lay the work face upwards in a porcelain dish and pour the mordant over it to a depth of a quarter of an inch. Bubbles of gas will immediately form all along the scratched lines. Rock the dish gently from side to side or wipe the bubbles away with a feather. If they are allowed to remain the line will not be etched evenly, for the gas in them keeps the acid away from the work. As stated above, the time required to etch the pattern may be a few minutes or an hour or two. Watch the plate and try the depth of the biting from time to time with a needle. To stop out any part which is sufficiently bitten, remove the plate from the acid, rinse it in water and paint some of one of the grounds, described above, over the parts which are bitten deeply enough. When the biting is completed, remove the plate, rinse it in water, warm it and then thoroughly clean with turpentine. Then wash with hot water and soap. Dry in hot sawdust. Or, after the tur pentine, the work, if not composed of iron or steel, may be boiled out in sulphuric acid pickle as described on page 24. Etched patterns are often trimmed up with the graver. 

The recesses having been prepared in one of the ways described above, the inlaying must now be considered. There are three entirely different methods by which the pattern may be filled in. By the first the inlay is fused into the hollows. By the second it is deposited in them by the electroplating or the amalgamation process. And by the third it is hammered or burnished in. The first two are by far the most satisfactory, for the intimate union between inlay and inlaid, like that between a solder and the work soldered, ensures a perfect and permanent hold for the inlay. Any metal or alloy which can be used as a solder for another metal can be used as an inlay for it. Thus brass or silver solder may be used to fill recesses in copper; brass or gold in iron, etc. Flux must be used just as in soldering. To fill large spaces pieces of sheet metal or wire may be soldered in. When all the lines and spaces have been filled up and fired, all superfluous inlay and solder can be cleared away with a fine file, and the work polished smooth. Iron or steel weapons and armour " damascened " with gold in this way are well known. Soft solder may be used in a similar manner for the decoration, say, of copper. 

By the electroplating process any metal or alloy which can be electro-deposited may be used for inlaying, those parts of the work on which the deposit is not required being protected by a coat of wax or varnish. 

Damascening. Silver may be inlaid with gold in the following manner. Fine gold is filed to very fine powder and kneaded with an equal weight of mercury in the palm of the hand until an evenly mixed amalgam is obtained. The engraved silverwork is rubbed with " grey powder " (mercury with chalk). This slightly amalgamates the sur face. The gold amalgam is piled into and over the recesses, and the work left for a day or two. The amalgam should be pressed down in the hollows occasionally. The work is next placed on a warm hob so that the mercury may evapor ate slowly. Its fumes are very injurious, so avoid them. This gentle heating may go on for many hours, but the work must be heated at last to low redness to drive off every particle of mercury. Then burnish the gold well, scrape down and polish the work. 

When wire is to be used for the inlay the groove into which it is to be hammered must be wider below than at the surface of the work, Fig. 268. This undercut form may be produced by widening out the deep part of the groove first cut, or little additional grooves may be cut with a knife-edge scorper at each side of the bottom, Fig. 269. These afford sufficient key to hold the wire when it has been hammered in. An etched line, though rather uneven at the bottom, is not wide enough there to hold the wire safely. It must be widened out like the other. The gold or silver wire for inlay should be, if possible, of pure metal. It is softer than metal containing alloy, and it has a better colour. Anneal the wire, and lay one end of it in the groove. Take a hammer which is nearly flat on the face and tap the wire into the hollow. See that no part of the groove remains unfilled. Then file or scrape the whole surface level. In another kind of damascening the surface of the metal is roughened, and gold foil or layers of pure gold-leaf burnished on, or hammered on with punches. 

Japanese workers have another method. They take the piece of iron or steel which is to be inlaid, anneal it, and cement it firmly on to the resin block, which corre sponds with our pitch block. Then with a light hammer and a fine chisel the surface of the metal is hatched with a number of fine, parallel cuts, quite close together. The work is then turned round and a second series of cuts made at right angles to the first. A third and a fourth set in the direction of the diagonals complete this part of the work. The iron has now an even, dull, roughened surface, like a mezzotint plate. The design is formed of gold wire bent into shape on the plate, and tapped into it with a hammer; the microscopic spikes which form the surface of the iron penetrating the wire and holding it firmly. The work is painted over at intervals with lacquer—very little of which, however, is allowed to remain actually on the surface. It enters the pores of the iron and makes it proof against rust. The pattern then tells up in gold against the dull brown of the lacquered iron.