Transparent Alkaline Enamels

Lapis-lazuli Blue.

Yellow-brown.

Sea-green Jade.

Garnet.

Ivory.

Yellow Ochre.

Opaque Yellow.

Turquoise.

Green.

Camellia Green.

Olive Green.

Dark Violet.

Green.

Remarks.

Flux(1) .

95

44

52

82

52

45

47

93

35

45

89

92

30

(1) Melted together:

Antimony (oxide of) .

• • •

....

2

..

• • •

4

..

...

..

Minium . 30 or 35 parts.

Cobalt „

0.7

• • •

...

..

• •

...

...

...

...

...

• •

O.6

• a •

Sand .50 or 45 ,,

Pot. carb. 12 or 12 ,,

Copper ,,

4.3

...

0.7

• •

...

• •

• •

7

4

5

3.4

..

4

Sod. carb. 8 or 8 ,,

Iron ,,

....

8

1.8

• •

3

10

4

...

....

5

6.1

..

..

Manganese ,,

...

13

...

6

• • •

...

• •

...

...

...

2.5

7

...

Nickel „

...

• .•

...

5

• •

...

...

...

...

...

...

..

Lead (plumbate of)

...

25

...

25

25

25

25

...

55

25

...

..

55

Minium.

Potash (nitrate)

...

• •

...

5

...

• •

...

..

5

..

...

..

10

,, (carbonate)

...

• • •

..

...

...

• • •

. .

...

...

...

..

..

..

Sand

...

20

...

20

20

20

20

...

...

20

..

..

• ..

Sodium (borate)

...

• • •

...

...

...

...

...

...

5

...

..

..

5

Melted borax.

,, (oxide).

...

• •

5

..

• • •

..

...

...

..

..

....

Soda.

The different mixtures are melted, then crushed and applied to the biscuit or fired falfence. Application over engobe is not necessary, but this method gives more delicacy to the products.

In order to deposit a uniform layer of enamel we immerse in the coloured paste, which has been thickened by gum or some other viscous substance. If we wish to make reserves, we lay with a brush on the biscuit, in the places to be reserved, a coating composed of chalk and gum or essence, and immerse in the glaze. A moderate heat then causes the colour to adhere and the portions deposited on the reserves to fall off, thus leaving them bare. If coloured reserves are desired, the colour or colours which are different from those of the background are diluted with oil and applied with a brush to the required parts. Then, when immersion takes place, the colour of the background, which is diluted with water, does not adhere to the oil decoration.

Special effects are obtained by giving different thicknesses to the enamfels, either by running (p. 402), or by filling the hollows in the terra-cotta with enamel. In this case hollow impressions are made either by moulding or engraving on the pieces when fresh. If the design requires several pieces, as in the case of decorative panels, it is made up of quarries of this kind.

The effects obtained differ according as the transparent coloured enamels are applied to the paste when unfired, fired, or warmed (biscuit). When they are placed close together, they have a tendency to run together at the moment of fusion. This inconvenience may be avoided by tracing the outline of the design with a black and less fusible glaze of sufficient relief. The coloured enamels are applied within these outlines. This process, wrongly called cloisonne, was used by Deck in 1874, and has since spread with astonishing rapidity in France and abroad.

Decoration With Colours

In the case of enamels, the colour is incorporated in the glaze, which if transparent forms a coloured glass; it is otherwise in decoration with colours. Colour and glaze are applied separately; sometimes the latter covers the former, and this is under-glaze decoration; sometimes it is the reverse, and we have over-glaze decoration.