274 ENAMELS 



Below tho shelf E, a square hole, n, is seen, which serves for admitting air, and for 

 extracting the ashes. Similar holes are left upon each side of tho surface. 



On a level with tho shelf, in the interior of tho furnace, a thin fire-tile I rests, per- 

 forated with numerous small holes. This is tho grate represented in a ground v'n-w 

 in fiq. 825. Figs. 828, 829, 830, represent, under different aspects, tho inufile : Fiff. 

 828 shows the elevation of its further end ; fig. 829 its sides ; and Jit/. 830 its front 

 part. At J, Jiff. 827, tho muffle is seen in its place in tho furnace, resting on two bars 

 of iron, or, still better, on lodges of fire-clay, supported on brackets attached to tho 

 lateral sides of tho furnace. Tho muffle is niado of earthenware, and as thin ns 

 possible. Tho fuel consists of dry beech wood, or oaken branches, about an inch in 

 diameter, cut to tho length of nine inches, in order to be laid in horizontal strata 

 within tho furnace, one row only being placed above the muffle. When the muffle 

 has attained to a white red heat, the sheet-iron tray, bearing its enamel plate, is to bo 

 introduced with a pair of pincers into tho front of tho muffle, and gradually advanced 

 towards its further end. Tho mouth of tho muffle is to bo then closed with two 

 pieces of charcoal only, between which the artist may see tho progress of the operation. 

 Whenever the enamel begins to flow, the tray must be turned round on its base to 

 insure equality of temperature ; and as soon as tho whole surface is melted, tho tray 

 must bo withdrawn with its plate, but slowly, lest the vitreous matter bo cracked by 

 sudden refrigeration. 



Tho enamel plate, when cold, is to be" washed in very dilute nitric acid, and after- 

 wards in cold water, and a second coat of granular enamel paste is to be applied, with 

 the requisite precautions. This being passed through tho fire, is to be treated in the 

 same way a third time, when the process will be found complete. Should any chinks 

 happen to the enamel coat, they must be widened with a graver, and tho space being 

 filled with ground enamel, is to be repaired in the muffle. The plate, covered with a 

 pure white enamel, requires always to be polished and smoothed with sandstone 

 and water, particularly if the article have a plane surface ; it is then finally glazed at 

 the fire. 



The painting operation now follows. The artist prepares his enamel colours by 

 pounding them in an agate mortar, with a pestle of agate, and grinding them on an 

 agate slab, with oil of lavender, rendered viscid by exposure to the sun in a shallow 

 vessel, loosely covered with gauze or glass. The grinding of two drachms of enamel 

 pigment into an impalpable powder will occupy a labourer a whole day. The 

 painter should have alongside of him a stove in which a moderate fire is kept up, for 

 drying Ms work whenever the figures are finished, It is then passed through tho 

 muffle. 



The following was the process adopted by Henry Bone, B.A., and his son, Henry 

 Pierce Bone, who produced the largest enamels ever painted; and beyond the time 

 expended in producing them and consequent expense there appears no practical limit 

 to the size of enamel paintings. 



Preparing the plate. For small plates (up to two inches long) pure gold is the best 

 material. Silver (quite pure) is also used, but is apt to get a disagreeable yellow 

 colour at the edges by repeated firings. For larger sizes, copper is used. The copper 

 should be annealed until quite free from spring, and then cleaned with dilute sulphuric 

 acid (one part acid, four water), and shaped in a wooden mould, afterwards used in 

 making tho plate so. as to produce a convex surface, varying according to tho size of 

 the plate, taking care that tho shaping does not reproduce the spring in tho copper, 

 in which case the process must be repeated. If tho place is not raised in tho centre, 

 in the course of repeated firings the corners will rise irregularly, producing undulations 

 over the plate, perfect flatness being next to impossible for large pictures. Tho 

 copper is then laid face downwards on tho convex wooden mould used for shaping, 

 and enamel, ground fine with water, is spread over it with a small bono spoon ; when 

 covered, a fine cloth doubled is pressed gently on it to absorb tho water, and then it is 

 smoothed with a steel spatula. This forms tho back of tho plate, and when fired this 

 part is finished. The copper is now reversed on a convex board tho exact counter- 

 part of the other, and covered with white enamel ground fine in tho same way as 

 above. The plate is now ready for firing, and after it has been fired and cooled, tho 

 surface must be ground smooth with a flat piece of flint or other hard substance, with 

 silver sand and water. It must next bo covered with a softer and more transparent 

 kind of enamel called flux, ground and spread on in the same way as the first enamel, 

 but this time only on the faco of tho plate. This is fired as before, and when cool the 

 surface must bo again ground smooth, and when glazed in tho furnace, the plat-- is 

 finished. For the first coat a white solid i-nanu-1 is used to prevent tho green colour 

 from tho oxidised copper showing through ; tho second coat is a softer enamel, to 

 enable the colours used to melt with less heat. 



Firing. Tho plate is placed on a plnnche of fircstone. or well-baked Stourbridge 



