CHAPTER XXIV 

Enamelling {continued) Painted enamels—Preparation of plaque—Backing—Grinding colours in mortar—Applying the enamel—Drying—Firing—Foil—Grinding colours on slab—Painting—Gold—Alterations—Grisaille, etc. 

Painted Enamels. 

Champleve and cloisonne enamels had been made for many centuries before it was discovered that the metal outlines between the different colours were not essential to the permanence of the work, valuable though they were from the decorative point of view. Towards the end of the fifteenth century the craftsmen at Limoges in France, who did a good trade in enamelled shrines, caskets, croziers and other decorated metalwork began,inthe enamelled pictures which they fitted into the work, to leave out the metal divisions altogether. The way in which they worked has been followed, with little variation, by enamellers ever since. It is this,—you wish to make an enamelled plaque witha design paintedonit. Take a sheet ofcopper, or ofwhatevermetalyouareto use, measuring say,3 inches by 2, size 6, and dome it up slightly in the middle, Fig. 284. It is well to make it turn rather quickly downwards near the edges, leaving all the centre in a gentle curve, like Fig. 285, not like 286. This may be done by running a burnisher repeatedly round the metal about J inch from the edge, while the whole piece is held at an angle of 45° to the stake or bench. Then rub the burnisher across the plate from side to side in every direction until the centre is sufficiently raised. If the metal gets too hard first, you must anneal it. Insteadof usingtheburnisheryoucanshapetheplaque on a stake with the hammer alone, if you know how to planish. But in any case it is well to anneal the plaque when you have finished shaping it. Next file the edge so that the plaque will stand quite truly on the surface plate. The file will leave a little rough burr all round the edge. Leave this, for it will help to keep the first coat of enamel on. If the plaque is not to be covered all over with the same enamel at first, but with a number of different colours to form a pattern, you must now draw the design on the metal. Transfer it with carbon paper and carefully scratch it in Avith a steel point. You may now boil the plaque in sulphuric acid pickle (water 20 parts, acid 1 part) or leave the plaque in the cold pickle for an hour. Next scrub thoroughly with a nailbrush both under and upper surfaces with pumice powder and water. Leave the plaque in a covered dish of clean water, and get the enamels ready. 

Both sides of the plaque must be covered with enamel. To understand the reason for this, it will be well to consider first what would happen if the enamel were put on one side only. When the work was put into the furnace the metal would expand, and the fused enamel would settle down into close contact with it. When the work was taken from the furnace and cooled, both metal and enamel would contract. But the metal would contract much more than the enamel, for such is its nature. The result of this uneven shrinkage would be that a considerable strain would be put on the rather brittle enamel,—which would probably fly off, particularly if it were jarred in any way. Also, at the second and subsequent firings, the metal, being a better conductor of heat than the glass, would expand sooner, and again vary the stress on the glass. To avoid these dangers it is usual to cover both sides of the metal with enamel. The metal now, on cooling, cannot curl away from the enamel, as it did before. Nor can it contract more than the enamel, for it is gripped on both sides by it. It is, therefore, kept inits expandedstate, andadapts itselftothenew conditions —by stretching, as it were. That this is actually the case may be proved by measuring an enamel before and after firing it, say, a dozen times. It will be found to have grown perhapsaneighthofaninchinsixinches. Forthis reasonthe settings for large enamels should be made only when the firing has been completed. Inlaid enamels are sometimes backediftheyshowapersistentinclinationto flakeoff. The doming-up of the plaque serves several purposes : it keeps the enamel on its underside from contact with the ground, it preserves the middle of the plaque from collapse, and its corners from curling up. The whole work is rather stronger. 

Grind the enamels you are to use, wash them thoroughly, and put them into covered vessels with a little water. When washing translucent enamels always go on until the water which is poured off is quite clear from the milky tinge mentioned above, page 187. Fill the mortar with water, and wait a few seconds for the enamel to settle, then pour out the water. Repeat this as often as necessary. Do not throw away the sediment which will be found at the bottom of the vessel into which the water is poured. It is composed principally of finely ground enamel. It is quite good enough to use on the underside, or back, of the work. If an agate mortar is used the enamels require less washing : but agate mortars are expensive. Sets of little china pans, fitting one over the other, such as are sometimes used for water­colours, are useful for keeping small quantities of ground enamel free from dust. Ground enamel should always be kept wet. 

Lift the plaque by its edges (do not touch the face) and lay it, concave side upwards, on a piece of clean blotting paper. Take some of the sediment from the washings, or any finely ground enamel which you wish to use up, and spread it evenly over the plate. You may add a drop or two of a solution of gum tragacanth or of saliva to assist in keeping it from falling off when the plaque is turned over, though if the work is handled carefully it will do without the gum. You may apply the enamel with a brush or spatula. It must be spread evenly, and be just thick enough to hide the metal. As a rule the enamel on front and back of the plaque should be equal in thickness. Dry the backing by pressing a piece of blotting paper firmly upon it. Turn the work over and stand it on the table or on a dry piece of blotting paper: not a sodden piece, or some of the backing may come off. The design—scratched inbefore the plaque was cleaned—will still be visible. Fill it in with the proper colours, taking care to keep the edge of the ground enamel exactly to the drawing. If you put a drop of the gum tragacanth solution into the enamel on the plaque it will help to keep it together. Dry each patch of colour by touching its edge with blotting paper. Let it get nearly dry before you put the next colour up against it. The water will naturally run from the wet enamel into the dry, but you get a truer line between the colours if one is pretty dry first. You may, of course, mix the colours jtogether as much as you like if they are all of the same hardness. The enamel should be spread evenly all over, but should not be thicker than is necessary to cover the surface completely. Do not let it get wet enough near I the edges of the plaque to run on the table. When the plaque is completely covered, dry off the water with clean blotting paper. Lift it with the palette knife to the iron plate on which it goes into the furnace. Put both upon the top of the furnace to dry. Keep the work free from dust. 
When it is quite dry fire it. 

When the enamel comes from the furnace and has cooled down, look it over carefully. Some of the back may have fallen off. If so, it must be repaired. Cracks due to the uneven support given to the metal may appear on the sur face of the work. Scrape the metal quite clean at all bare places on both back and front, washing over the scrapededges with fluoric acid and afterwards with water, to avoid milkiness. Then repair the enamel and fire again. 

If you give the copper plaque a coating of clear flux first, andthenputthe colouredenamelsoverthat,they will show up much more brilliantly. Copper, with a coating of clear flux over it, looks a bright golden or a pink coppery colour according to the composition of the flux used. Silver seen through flux looks like white satin. The colour of gold hardly changes at all. Any drawing on the metal, whether scratched in with a steel point, or drawn with a lead pencil, will show clearly through the flux. The surface of the flux may, however, be roughened, then washed over with fluoric acid to avoid milkiness in the colour (see above) and the design transferred to it. The coloured enamels are then applied in their proper places. 

You have now the plaque with its first coat of coloured enamel fired on to it. The colours may require modifying, shading may be necessary; you may want to use some gold or silver foil to make a more brilliant patch of colour some where ; you may wish to put an outline round parts of the design, or touches of gold. Some or all of these things may be necessary. Now, as already stated, enamels vary in their hardness, some requiring much greater heat to melt them than others. The hardest coloursshould therefore be put on first, the softer ones for a later firing. A plaque may be fired a dozen or more times, but the enamel put on for the later firings should not require heat enough to disturb the harder enamel put on first. So you must find out which colours require the most heat. To do this you take a little of each of those you wish to use and arrange them in a row on a clean plaque and put it in the furnace. Then you note carefully the order in which they melt as the plaque gets hot; then you can go ahead. First put on the foil. This is thin sheet gold, silver or platinum. Small pieces, or " paillons " of this are laid on the enamel and covered with transparent colours. They are used to brighten up the enamel where necessary, colours looking much brighter when fired over these metals than over copper. Pure gold foil can be bought from dealers in dentists' materials, a leaf 4 inches square costing 2s. If you were to put gold leaf on the enamel as it is, it would be likely to crinkle or bubble up owing to the air between it and the enamel. To overcome this difficulty, and to make it easier to handle and cut to shape, it is well to stick the leaf between two sheets of gummed tissue paper. Then stab the leaf all over with a bundle of fine needles stuck in a cork. About 200 holes to the square inch will do. Now draw the design on the tissue paperandcutoutthe shapeswithscissors. Thepapermay be soaked off in water. Stick the paillons down on the enamel with a little gum tragacanth. The dentist's gold, having been annealed before purchase, will lie flat when fired. Gold which is not annealed will crinkle. Silver foil must be treated in the same way as the gold. But, owing to its fusibility, its use is sometimes abandoned in favour of plati num. If the foil was now covered with enamel its edges would show up too strongly; they must therefore be shaded. Do this with iridium black and fire it. If this shading is satisfactory you may put finely ground (and washed) colour wherever necessary and fire that. For shading, however, you must use enamel ground finely enough to paint with. 

Take a slab of plate glass, a foot square, and a glass muller, Fig. 279. See that they are both clean, and put a little of the colour you wish to use in the middle of the slab. You have now to grind it finely enough to use as paint. This will take time, but you must go on grinding till there is not a trace of grittiness to be seen in the colour where, near the edges of the slab, it is getting dry. Add a little water when necessary. The finely ground enamel must now be washed. It is not easy to do this without losing a good part of it. But most of the milkiness must be got rid of, or it will show up on the work. Keep that part which is nearest in colour to the enamel before it was ground. 

To use finely ground enamel to paint with, take a drop of oil of spike lavender to mix with the colour. They will flow 
fairly smoothly from the brush if they have been evenly mixed. You may add a little fat oil of turpentine if the paint dries too soon in hot weather. But the addition of a large proportion of medium of any kind will tend to make the 
colour bubble up in the furnace, so use as little as possible. Put in all the shading necessary. Then stand the enamel in a warm place to dry off as much of the medium as possible before the work goes into the furnace. Some of the shading sinksineachtimetheenamelis fired, soyoumuststrengthen it where necessary. Black enamel, ground finely, turns rather grey, so if you require a very strong black line you should use iridium black. This can be bought ready prepared. 

When all the painting is completed the gold may be put on. This can be bought in bottles from dealers in china colours, or the gold which is sold in shells at about a shilling each may be used. The liquid gold can be made from the following ingredients— 
Lavender oil 900 parts 
Gold chloride 100 Parts
Bismuth subnitrate Parts
Chrome soap 50 Parts

Wash the enamelled plate with spirit before putting on the gold. The latter must be well dried before firing. Not much heat is required to fix it. Gold from a gold shell looks brighter in most lights than the liquid gold,—which is similar to that so generally used on china goods. 

It sometimes happens that an enamel curls out of shape during firing. It can be straightened in the following manner. Have ready two large, stiff palette knives. See that they are quite clean and free from dust. With one of the knives lift the enamel straight from the furnace on to a flat stake or smooth slab of stone. Instantly push down any projecting corners, using both knives near the edges of the plaque to press the work into shape. Hold the edges down till the red glow has quite gone from the work. The enamel will be quite soft when it comes from the furnace, but in a few seconds will have set hard—when any pressure would have disastrous results. 


To remove a part of the enamel after it is fired is not so difficult a task as it looks at first sight. You can either 
dissolve the enamel at the offending spot with fluoric acid, or you can boldly cut it out with a graver. In the latter case it is well to wash the spot afterwards with fluoric acid to avoidany subsequent milkiness in the colour. 

Throughout all the work, absolute cleanliness of all the tools and materials is essential if you are to produce enamels free from specks. 

It is not unusual to employ china colours for the final touching up of an enamel. But this practice is not to be recommended, as the colours have not the same quality as enamel itself. They are principally composed of mineral oxides, without flux. They may sink into the enamel and become incorporated with it, but as a rule they must be covered with a thin film of soft flux to protect them from the action of the atmosphere. 

In the sixteenth and seventeenth centuries a large amount of work was done in grisaille on blue or black grounds. 
The copper was first covered allover with thedark-coloured ground. Then the designs were painted in monochrome, by successive layers of white enamel. Many coats of this were fired one over the other, till the light was sufficiently strong. The shading was given bythedark ground showing through the white. Sometimes little touches of colour were added, and gold. Much of the work shows wonderful technical ability, for the drawing and shading are excellent in spite of the difficulty of the medium. But, of course, all feeling for colour as such,is absent. 

A ground of white enamel may be spread directly on to the metal, and fired. It is then ground level, and coloured 
enamels are painted over it. Much work in this fashion was done in the eighteenth century at Battersea and else 
where. But, dainty though much of it is, it has lost the true quality of enamel,—the work being little different from china painting. White enamel is, however, sometimes painted over a portion of an enamelled plaque, shaded, and 
afterwards coveredwith a thin glaze of colour. The ground white enamel may be mixed with heavy paraffin oil as used for lubrication, or with vaseline diluted with paraffin and painted on with a brush. Dry it very thoroughly before firing. 

Enamelling being so much akin to glasswork, it is not surprising that the two crafts are sometimes combined. For instance, enamel colours are often used on glasswork. An unusual method is employed, however, in some of the enamels on the Ardagh Chalice in the National Museum, Dublin. A hemispherical blue glass bead has a recess carved or moulded in its surface. This recess is lined with a grey enamel and afterwards filled up with red. Other enamels on the same cup have a silver cell let into a glass or enamel bead, the cell being filled up afterwards with enamel 
of a different colour.