| Delia Robbia. | Majolica. | Delft. Faience. | French | |
| Silica | 49.65 | 48.00 | 49.07 | 48.65 |
| Alumina | 15.50 | 17.59 | 16.19 | 17.05 |
| Lime | 22.40 | 20.12 | 18.01 | 19.43 |
| Magnesia | 0.17 | 1.17 | 0.82 | 0.27 |
| Oxide of iron | 3.70 | 3.75 | 2.82 | 4.33 |
| Carbonic Acid, water, &c. | 8.58 | 9.46 | 13.09 | 10.27 |
2. Shaping.—The vessels were either “thrown” on the potter’s wheel (which had remained practically unaltered from Egyptian times), or they were formed by “pressing” thin cakes of clay into moulds, made of a composition of plaster (gesso), bone-ash and marble dust. In the latter way all shapes that were not circular were made, as well as those with heavy bosses or gadroons imitated from embossed metal forms. It is interesting, though not surprising, to note that for the fine later wares, the roughly thrown vases, when sufficiently dry, were recentred on the wheel or were placed in a joiner’s lathe and smoothed to a clean and accurate surface. The Greek potters did the same, and this practice must always be followed where fine painting or gilding is afterwards to be applied. In the later florid vases of the Urbino style the piece was built up of thrown parts and moulded parts (handles, masks, spouts, &c.), luted together with slip when they were dry enough to be safely handled, and then retouched by the modeller or vase-maker, a method followed to this day for elaborate pieces of pottery or porcelain.
Plate V
| Rhodian or Turkish: 16th century. | Syro-Persian: 13th century. |
| Rhodian or Turkish: 16th century. | Rhodian or Turkish: 16th century. |
| Damascus: 16th century. | Persian, lustre and underglaze colour: 13th century. |
3. The Glaze.—The white enamel which formed at first both the glaze and the ground for painting upon—bianco, as it was called—was prepared in a complicated way. A clear potash glass (marzacotto) was made by melting together clean siliceous sand (rena) and the potash salt left as the lees of wine (feccia). This corresponds to the alkaline glaze of the Egyptians with the substitution of potash for soda. Such a glaze alone would have been useless to the Italian potter, and accordingly the bianco was made by melting together thirty parts of marzacotto and twelve parts of lead and tin ashes. The white enamel as used was therefore a mixed silicate of lead and potash rendered opaque with oxide of tin.
4. Pigments (colori) were compounded from metallic oxides or earths; the yellow, from antimoniate of lead, which was mixed with oxide of iron to give orange; the green, from oxide of copper (the turquoise tint given to the Egyptian and Syrian glazes by oxide of copper is impossible with a glaze of lead and tin); and the greens were made by mixing oxide of copper with oxide of antimony or oxide of iron; blue, from oxide of cobalt, used in the form of a blue glass (smalto, or zaffara); brownish-purple, from manganese; black, from mixtures of the other colours; and the rare red, or reddish brown, of Faenza and Cafaggiolo was probably the same Armenian bole that was used so magnificently by the makers of the Turkish pottery, but on the white enamel ground this colour was most treacherous and uncertain. It must be remembered that many of these colours owe their tint to the lead used in their composition, or to the grounds containing oxides of lead and tin on which they were painted. Piccolpasso describes the preparation and composition of the various colours used in his day.
5. Coperta, or transparent glaze. In the later majolica a thin coating of soft rich glaze was applied over the fired painting to give a smooth bright surface. This coperta was a soft lead glass consisting of silica (sand), 20 parts; oxide of lead, 17 parts; potash, 12 parts; and common salt, 8 parts; fused together and then finely ground in water.
6. Methods of Glazing and Decorating.—In the mezza-majolica and the early majolica it is probable that the clay vessel was dipped in the white bath to give it an envelope (invetriatura) before it was fired at all; but it must soon have become apparent that it was much better to fire first the shaped vessel until it was about as hard and brittle as a clay tobacco-pipe, and then coat it with the white enamel, by dipping it into a bath or pouring the fluid material upon it. This was the practice described by Piccolpasso. A coating of white enamel, the thickness of glove leather, having been obtained, the piece was carefully taken by the painter, who first etched in the outline on the absorbent powdery ground, and then shaded the figures, landscapes, &c., in blue or in a mixture of blue and yellow, adding the other colours as gradated washes. The vase was then fired a second time to a heat greater than the first, so that the enamel was melted on the vessel and the colours sunk into the enamel at one and the same operation. This method of painting on the unbaked enamel demanded a bold direct treatment—for alteration or retouching was impossible—and much of the vigour of the earlier designs is due to this fact. As the ware became more refined in its treatment it was felt that this method did not yield a sufficiently brilliant surface, and so the painted and fired piece was coated with a film of coperta and fired again at a slightly lower temperature to make it smoother and more glossy. Still pursued by the idea of rivalling the triumphs of pictorial art, the majolist carried his methods a step farther. The white enamel coating was fired before painting, giving a glossy surface on which the painter could draw or wipe out, and so could execute outlining, tinting, or shading of the utmost delicacy. A film of coperta was then washed over the painting, and the piece was fired a third time in the cooler parts of the kiln. In some instances it is not easy even for an experienced potter to decide which method has been pursued, owing to the softening of the colours. Generally we should expect that the later and more pictorial pieces had been painted on a ground of fired white enamel, and we may be absolutely certain when delicate white patterns have been “picked out” in a coloured ground.
Where lustre decoration has been added to a piece of majolica it indicates, as elsewhere, the use of a special process, and a final firing at a lower heat. The lustre pigments were the same as those used on the earlier lustred wares, and these were painted over an otherwise finished piece. To obtain the lustre effect these were placed in a special kiln, so contrived that when the pots were just visibly red the smoke of the burning fuel (rosemary or gorse) was allowed to play upon them long enough to drive the metallic films (silver or copper) into the already-fired glaze.[17]
Collections.—The Victoria and Albert Museum contains perhaps the most widely representative collection in the world, especially as at the present time the pieces of the Salting and Pierpont Morgan collections are on exhibition there. The British Museum collection is valuable, being rich in “signed” pieces of the first quality. The Wallace collection and the Ashmolean Museum at Oxford (Fortnum collection, &c.) are also valuable and contain some remarkable examples. The Cluny Museum, the Louvre and the museum at Sèvres have fine collections; while noteworthy pieces are to be found in the Ceramic Museum at Limoges. In Germany the museum at Brunswick contains one of the largest collections known, but many inferior and doubtful examples. Berlin, Munich, Vienna and St Petersburg have noteworthy collections. In Italy, the Bargello at Florence and the museums of Venice, Milan, Turin, Faenza, Pesaro, Urbino, Rome and Naples all have collections, whilst interesting examples of local manufactures are to be found in many of the smaller Italian towns. The American museums, especially those in New York, Boston and Philadelphia, have some fine examples.