CHAPTER XXIII 

Enamelling {continued) Cloisonne enamels—Making, fitting and soldering cloisons—Plique a jour Temporary backgrounds—Bassetaille enamels. 

Inlaid Enamels, (b) Cloisonne. 

In this work the recesses for the different coloured enamels are formed by narrow strips of metal or wire which are fastened on to the background, Fig. 281. It differs, therefore, from champleve work, in which the recesses are carved out from a thick piece of metal, leaving the divisions standing up. Champleve work was generally executed in copper or bronze; cloisonne work probably arose when the old craftsman began to enamel on gold, less of the precious metal being required by this process. The wire used by Byzantine workers was about 1/100 inch thick and 1/50 to 1/32's inch high. 

To make a cloisonne enamel, transfer the design to a thin sheet of metal in the ordinary way, then scratch it in with a steel point. Draw down some gold wire of oblong section till it is little more than •£? inch wide, and size 1 or 2 on the metal gauge in thickness. Anneal it. Then with fine pliers bend it to the shape required, trying it from time to time against the design. Cut it off where necessary with a sharp chisel against a smooth piece of brass, not with shears. With the chisel you can cut the end at exactly the angle you wish. If there are many cloisons to be got ready it is well to gum them on to a piece of glass or card to keep them safely. When all are prepared, clean the back plate, and fasten down each cloison in its place with borax with which a little gum tragacanth has been mixed. This will keep the cloison in place when the borax boils up; or the cloisons may be fixed with gum alone at first, the borax and solder being afterwards applied. The solder used should be as hard as possible, composed, say, of 4 parts silver to 1 of copper. For silverwork it should be free from zinc, for this ingredient burns out in the firing and shows as a dark stain through the enamel. It may even cause the enamel to chip off above it. It is well, therefore, to allow as little of the solder as possible to flow on to the background. The Japanese do not now solder the cloisons down at all. They fix them with rice paste or gum and proceed at once to fill in the enamel. When this is fired it holds the cloisons firmly. However, it is a good plan to solder down some at least of the cloisons, the outside ones and the principal divisions, say. They are otherwise inclined to float about with the enamel. Any solder which would be exposed to the direct heat of the furnace should be covered up with rouge or whiting before each firing, otherwise it might run or burn. In either case considerable damage might be done. When all the soldering is completed the work must be boiled out in pickle. Back ground and cloisons should then be scraped bright, any loose cloisons put in place, and the enamel filled in. The work then proceeds just as described for champleve. 

Inlaid Enamels, (c) Plique a jour. 

Enamels of this type have no background. They are like miniature stained-glass windows, the lead lines in the windows being represented by the metal cloisons in the enamel. The filigree wire pattern which is to hold the enamel is built up in the ordinary way, see page 60, or it may be in some cases formed from a thick sheet of metal pierced with holes of suitable shapes. In either case those parts of the work to which the enamel is to hold are scraped bright and clean. The work is then, with U-shaped iron-wire clamps, fastened down temporarily on to a sheet of some material to which enamel will not stick. Now there are several such materials—platinum, aluminium-bronze, or mica—these leave the underside of the enamel clean and smooth after firing; and tripoli, fireclay or pumice—which do not. Take, say, a sheet of aluminium-bronze, size 10, a little larger than the work, burnish one side and lay the wire network on to it. Tie or clamp the wires down, so that they will not move while you are filling in the enamel, Fig. 282. Proceed just as in champleve work. Remember always to cover up any solder with rouge or whiting before each firing. When the firing is completed remove the clamps. Give the bronze a few light taps if necessary, and it will come away from the enamel at once. The underside of the enamel should then be very carefully polished. If you use mica for a temporary background it is well to lay it on a piece of iron, and to clamp the wires round that. If the enamel is to take a curved shape the platinum or aluminium-bronze background must first be hammered to that shape, and the wire work made to fit. A very beautiful piece of work in the museum at South Kensington is illus trated in Fig. 382. The enamel here is in very high relief,—cabochon shape. Such a work could be executed by piling up the enamel high above the cloisons by repeated application of fresh enamel to that already fired. Or by preparing a platinum or aluminium-bronze plate in which de pressions are made to correspond with the bosses of enamel. The gold cloisonne pattern would be clamped upside down on to this and the recesses filled with enamel in the ordinary way. It probably would be well to use largish lumps of enamel, instead of finely ground powder. Other works by the same artist, Count Suau de la Croix, have enamel in high relief on both sides of the wirework. This would indicate, I think, that the recessed background was used, and that the enamel was piled up high above the cloisons also. M. Fernand Thesmar of Paris has also executed some wonderful works in plique a jour enamel. One of these, a little bowl, is in the South Kensington Museum. 

There are other ways by which plique a jour enamels may be executed. The temporary background for the enamelling of a bowl is formed from the sheet copper, and gold wire is used for the cloisons. When the enamelling is completed, the copper bowl is dissolved by the action of nitric acid, the gold and enamel being unaffected. There is yet another manner in which work of this kind may be fired. The metal framework is supported in a vertical position on the plate which goes into the furnace, Fig. 283. Each opening is then carefully filled with enamel, with which is mixed a little gum tragacanth. The work is carefully dried and put into a very hot furnace. It is removed before the enamel has time to run down. The gaps are then filled up and the firing repeated. Work of this kind is very fragile, and looks as though a soap-bubble had been blown on to the wires. 

Transparent Enamels. Bassetaille. 

^In this work the design is carved in low relief at a little distance, ^ to ^ inch, below the surface of the work—very much as described above for champleve. But in this case the different colours are not separated by metal lines as by that process. They are laid down side by side in close contact. In both, the enamel is filled in to the originallevel of the metal, and polished smooth,—the strengthof the colour varying with the depth of the relief. The carving of the relief must, of course, be done with very great care, for the work will be clearly seen through the enamel. Water colour paint floated over the relief will help you to judge the depth of the cutting. Bassetaille enamellingis executed as a rule on gold or silver. Perhaps the finest example extant is the St. Agnes Cup in the British Museum, Fig. 380. 

In applying the colours it is well to mix a little gum tragacanth with each as you put it in its place, and to allow each patch of colour to dry a little before you lay the next alongside it. If you do this very carefully you can keep each colour from spreading beyond its proper limits. Hard enamels should be used, for they are less likely to spread than soft enamels, and they wear better. 

In some cases it is more convenient to prepare the metal base for the enamel by repousse work than by en graving or carving. The metal employed for this work is naturally much thinner, perhaps size 4 or 5. Metal as thin as this can only be enamelled safely, if it is covered with a layer of enamel on the underside as well as on the face. The reason for this is given in the next chapter. 

Cast work can be enamelled, though the enamel has a great tendency to flake off—days or perhaps months after 
the work is completed: but a careful preparation of the ground will considerably lessen this danger. The edges of the recesses should be slightly undercut; the whole ground should be pecked over regularly with the graver—to givethe enamel a good key; and the work, when done, should be very carefully annealed, by being allowed to remain in the furnace while it cools down, as described above.