Henley's Twentieth Century Formulas, Recipes and Processes

by Unknown

CERAMICS

GROUND CERAMICS—LAYING OIL FOR: See Oil.

Notes For Potters, Glass-, And Brick-makers.

To arrest the unsightly defect of “crazing,” the following have been the most successful methods employed, in the order given:

I.—Flux made of 10 parts tincal; 4 parts oxide of zinc; 1 part soda.

II.—A calcination of 5 parts oxide of zinc; 1 part pearl ash.

III.—Addition of raw oxide of zinc, 6 pounds to each hundredweight of glaze.

To glazed brick and tile makers, whose chief difficulty appears to be the production of a slip to suit the contraction of their clay, and adhere strongly to either a clay or a burnt brick or tile, the following method may be recommended:

Mix together:

Ball clay	10 parts
Cornwall stone	10 parts
China clay	7 parts
Flint	6 1/2 parts

To be mixed and lawned one week before use.

To Cut Pottery.

Brick and Tilemakers’ Glazed Bricks:

White.

No. 1 Slip.—

Same clay as brick	9 parts
Flint	1 part
Ball clay	5 parts
China	4 parts

Allow the brick to remain slowly drying for 8 to 10 hours, then when moist dip in the white body.

White Body.—

China clay	24 parts
Ball clay	8 parts
Feldspar	8 parts
Flint	4 parts

The brick should now be dried slowly but thoroughly, and when perfectly dry dip the face in clean cold water, and immediately afterwards in glaze.

Hard Glaze.—

Feldspar	18 parts
Cornwall stone	3 1/2 parts
Whiting	1 1/2 parts
Oxide of zinc	1 1/2 parts
Plaster of Paris	3/4 part

{165}

Soft Glaze.—

White lead	13 parts
Feldspar	20 parts
Oxide of zinc	3 parts
Plaster of Paris	1 part
Flint glass	13 parts
Cornwall stone	3 1/2 parts
Paris white	1 1/4 parts

Where clay is used that will stand a very high fire, the white lead and glass may be left out. A wire brush should now be used to remove all superfluous glaze, etc., from the sides and ends of the brick, which is then ready for the kiln. In placing, set the bricks face to face, about an inch space being left between the two glazed faces. All the mixtures, after being mixed with water to the consistency of cream, must be passed 2 or 3 times through a very fine lawn. The kiln must not be opened till perfectly cold.

Process For Colored Glazes.

Preparation Of Colors.

Turquoise.—
Oxide of zinc	8 parts
Oxide of cobalt	1 1/4 parts
Grass Green.—
Oxide of chrome	6 parts
Flint	1 part
Oxide of copper	1/2 part
Royal Blue.—
Pure alumina	20 parts
Oxide of zinc	8 parts
Oxide of cobalt	4 parts
Mazarine Blue.—
Oxide of cobalt	10 parts
Paris white	9 parts
Sulphate barytes	1 part
Red Brown.—
Oxide of zinc	40 parts
Crocus of martis	6 parts
Oxide of chrome	6 parts
Red lead	5 parts
Boracic acid	5 parts
Red oxide of iron	1 part
Orange.—
Pure alumina	5 parts
Oxide of zinc	2 parts
Bichromate of potash	1 part
Iron scale	1/2 part
Claret Brown.—
Bichromate of potash	2 parts
Flint	2 parts
Oxide of zinc	1 part
Iron scale	1 part
Blue Green.—
Oxide of chrome	6 parts
Flint	2 parts
Oxide of cobalt	3/4 part
Sky Blue.—
Flint	9 parts
Oxide of zinc	13 parts
Cobalt	2 1/2 parts
Phosphate soda	1 part
Chrome Green.—
Oxide of chrome	3 parts
Oxide of copper	1 part
Carbonate of cobalt	1 part
Oxide of cobalt	2 parts
Olive.—
Oxide of chrome	3 parts
Oxide of zinc	2 parts
Flint	5 parts
Oxide of cobalt	1 part
Blood Red.—
Oxide of zinc	30 parts
Crocus martis	7 parts
Oxide of chrome	7 parts
Litharge	5 parts
Borax	5 parts
Red oxide of iron	2 parts
Black.—
Chromate of iron	24 parts
Oxide of nickel	2 parts
Oxide of tin	2 parts
Oxide of cobalt	5 parts
Imperial Blue.—
Oxide of cobalt	10 parts
Black color	1 1/2 parts
Paris white	7 1/2 parts
Flint	2 1/2 parts
Carbonate of soda	1 part
Mahogany.—
Chromate of iron	30 parts
Oxide of manganese	20 parts
Oxide of zinc	12 parts
Oxide of tin	4 parts
Crocus martis	2 parts
Gordon Green.—
Oxide of chrome	12 parts
Paris white	8 parts
Bichromate of potash	4 1/2 parts
Oxide of cobalt	3/4 part
Violet.—
Oxide of cobalt	2 1/2 parts
Oxide of manganese	4 parts
Oxide of zinc	8 parts
Cornwall stone	8 parts
Lavender.—
Calcined oxide of zinc	5 parts
Carbonate of cobalt	3/4 part
Oxide of nickel	1/4 part
Paris white	1 part
Brown.—
Manganese	4 parts
Oxide of chrome	2 parts
Oxide of zinc	4 parts
Sulphate barytes	2 parts
Dove.—
Oxide of nickel	7 parts
Oxide of cobalt	2 parts
Oxide of chrome	1 part
Oxide of flint	18 parts
Paris white	3 parts
Yellow Green.—
Flint	6 parts
Paris white	4 parts
Bichromate of potash	4 1/2 parts
Red lead	2 parts
Fluorspar	2 parts
Plaster of Paris	1 1/2 parts
Oxide of copper	1/2 part
Bodies Requiring No Stain:
Ivory.—
Cane marl	16 parts
Ball clay	12 parts
Feldspar	8 parts
China clay	6 parts
Flint	4 parts
Cream.—
Ball clay	22 parts
China clay	5 1/2 parts
Flint	5 parts
Feldspar	3 1/2 parts
Cane marl	12 parts
Black.—
Ball clay	120 parts
Ground ocher	120 parts
Ground manganese	35 parts
Buff.—
Ball clay	12 parts
China clay	10 parts
Feldspar	8 parts
Bull fire clay	16 parts
Yellow ocher	3 parts
Drab.—
Cane marl	30 parts
Ball clay	10 parts
Stone	7 parts
Feldspar	4 parts
Brown.—
Red marl	50 parts
China clay	7 parts
Ground manganese	6 parts
Feldspar	3 parts
In making mazarine blue glazed bricks use the white body and stain the glaze only.
Mazarine blue	1 part
Glaze	7 parts

For royal blue use 1 part stain to 6 parts white body, and glaze unstained.

Blood-red Stain.

Stain.—

Crocus martis	20 parts
Yellow ocher	4 parts
Sulphate of iron	10 parts
Red oxide of iron	2 parts

A still cheaper method is to put a slip or external coating upon the goods. The slip being quite opaque, effectively hides the natural color of the brick or tile upon which it may be used.

The process is to mix:

Blood-red stain	1 part
Good red clay	6 parts

Add water until the mixture becomes about the consistency of cream, then with a sponge force the liquid two or three times through a very fine brass wire lawn, No. 80, and dip the goods in the liquid as soon as they are pressed or molded.

Blue Paviors.

Stain For Blue Paviors.—

Ground ironstone	20 parts
Chromate of iron	5 parts
Manganese	6 parts
Oxide of nickel	1 part

Use 1 part clay and 1 part stain for coating, and 50 or 60 parts clay and 1 part stain for staining through.

Fire blue paviors very hard.

Buff Terra-cotta Slip.—

Buff fire clay	16 parts
China clay	6 parts
Yellow ocher	3 parts
Ball clay	10 parts
Flint	4 parts

Add water to the materials after mixing well, pass through the fine lawn, and dip the goods when soft in the liquid.

Transparent Glaze.—

Ground flint glass	4 parts
Ground white lead	4 parts
Ground oxide of zinc	1/4 part

This glaze is suitable for bricks or tiles made of very good red clay, the natural color of the clay showing through the glaze. The goods must first be fired sufficiently hard to make them durable, afterwards glazed, and fired again. The glaze being comparatively soft will fuse at about half the heat required for the first burning. The glaze may be stained, if desired, with any of the colors given in glazed-brick recipes, in the following proportions: Stain, 1 part; glaze, 1 part.

Special Recipes For Pottery And Brick and Tile Works:

Vitrifiable Bodies.

I.—	Cornwall stone	20 parts
	Feldspar	12 parts
	China clay	3 parts
	Whiting	2 parts
	Plaster of Paris	1 1/2 parts
II.—	Feldspar	30 parts
	Flint	9 parts
	Stone	8 parts
	China clay	3 parts
III.—	Feldspar	20 parts
	Stone	5 parts
	Oxide of zinc	3 parts
	Whiting	2 parts
	Plaster of Paris	1 part
	Soda crystals, dissolved	1 part

Special Glazes For Bricks Or Pottery At One Burning.

I.—	Cornwall stone	40 parts
	Flint	7 parts
	Paris white	4 parts
	Ball clay	15 parts
	Oxide of zinc	6 parts
	White lead	15 parts
II.—	Feldspar	20 parts
	Cornwall stone	5 parts
	Oxide of zinc	3 parts
	Flint	3 parts
	Lynn sand	1 1/2 parts
	Sulphate barytes	1 1/2 parts
III.—	Feldspar	25 parts
	Cornwall stone	6 parts
	Oxide of zinc	2 parts
	China clay	2 parts
IV.—	Cornwall stone	118 parts
	Feldspar	40 parts
	Paris white	28 parts
	Flint	4 parts
V.—	Feldspar	16 parts
	China clay	4 parts
	Stone	4 parts
	Oxide of zinc	2 parts
	Plaster of Paris	1 part
VI.—	Feldspar	10 parts
	Stone	5 parts
	Flint	2 parts
	Plaster	․1/2 part

The following glaze is excellent for bricks in the biscuit and pottery, which require an easy firing:

White.—

White lead	20 parts
Stone	9 parts
Flint	9 parts
Borax	4 parts
Oxide of zinc	2 parts
Feldspar	3 parts

These materials should be procured finely ground, and after being thoroughly mixed should be placed in a fire-clay crucible, and be fired for 5 or 6 hours, sharply, or until the material runs down into a liquid, then with a pair of iron tongs draw the crucible from the kiln and pour the liquid into a bucket of cold water, grind the flux to an extremely fine powder, and spread a coating upon the plate to be enameled, previously brushing a little gum thereon. The plate must then be fired until a sufficient heat is attained to run or fuse the powder.

Pottery Bodies And Glazes:

Ordinary.—

I.—	China clay	2 1/2 parts
	Stone	1 1/2 parts
	Bone	3 parts
II.—	China clay	5 parts
	Stone	2 1/2 parts
	Bone	7 parts
	Barytes	3 parts
III.—	Chain clay	5 parts
	Stone	3 parts
	Flint	1/4 part
	Barytes	8 parts

Superior.—

I.—	China clay	35 parts
	Cornwall stone	23 parts
	Bone	40 parts
	Flint	2 parts
II.—	China clay	35 parts
	Cornwall stone	8 parts
	Bone	50 parts
	Flint	3 parts
	Blue clay	4 parts
III.—	China clay	8 parts
	Cornwall stone	40 parts
	Bone	29 parts
	Flint	5 parts
	Blue clay	18 parts
IV.—	China clay	32 parts
	Cornwall stone	23 parts
	Bone	34 parts
	Flint	6 parts
	Blue clay	5 parts
V.—	China clay	7 parts
	Stone	40 parts
	Bone	28 parts
	Flint	5 parts
	Blue clay	20 parts

Finest China Bodies.—

I.—	China clay	20 parts
	Bone	60 parts
	Feldspar	20 parts
II.—	China clay	30 parts
	Bone	40 parts
	Feldspar	30 parts
III.—	China clay	25 parts
	Stone	10 parts
	Bone	45 parts
	Feldspar	20 parts
IV.—	China clay	30 parts
	Stone	15 parts
	Bone	35 parts
	Feldspar	20 parts

Earthenware Bodies.—

I.—	Ball clay	13 parts
	China clay	9 1/2 parts
	Flint	5 1/2 parts
	Cornwall stone	4 parts
II.—	Ball clay	12 1/2 parts
	China clay	8 parts
	Flint	5 1/2 parts
	Cornwall stone	2 1/2 parts
	One pint of cobalt stain to 1 ton of glaze.
III.—	Ball clay	13 1/4 parts
	China clay	11 parts
	Flint	4 parts
	Cornwall stone	5 parts
	Feldspar	4 parts
	Stain as required.
IV.—	Ball clay	18 1/2 parts
	China clay	13 1/2 parts
	Flint	8 1/2 parts
	Stone	4 parts
	Blue stain, 2 pints to ton.
V.—	Ball clay	15 parts
	China clay	12 parts
	Flint	6 parts
	Stone	4 parts
	Feldspar	4 parts
	Blue stain, 2 pints to ton.
VI. (Parian).—
	Stone	11 parts
	Feldspar	10 parts
	China clay	8 parts

Colored Bodies:

Ivory Body.—

Ball clay	22 parts
China	5 1/2 parts
Flint	5 parts
Stone	3 1/2 parts

Dark Drab Body.—

Cane marl	30 parts
Ball clay	10 parts
Cornwall stone	7 parts
Feldspar	4 parts

Black Body.—

Ball clay	120 parts
Ocher	120 parts
Manganese	35 parts
Cobalt carbonate	2 parts

Grind the three last mentioned ingredients first.

Caledonia Body.—

Yellow clay	32 parts
China clay	10 parts
Flint	4 parts

Brown Body.—

Red clay	50 parts
Common clay	7 1/2 parts
Manganese	1 part
Flint	1 part

Jasper Body.—

Cawk clay	10 parts
Blue clay	10 parts
Bone	5 parts
Flint	2 parts
Cobalt	1/4 part

Stone Body.—

Stone	48 parts
Blue clay	25 parts
China clay	24 parts
Cobalt	10 parts

Egyptian Black.—

Blue clay	235 parts
Calcined ocher	225 parts
Manganese	45 parts
China clay	15 parts

Ironstone Body.—

Stone	200 parts
Cornwall clay	150 parts
Blue clay	200 parts
Flint	100 parts
Calx	1 part

Cream Body.—

Blue clay	1 1/2 parts
Brown clay	1 1/2 parts
Black clay	1 part
Cornish clay	1 part
Common ball clay	1/4 part
Buff color	1/4 part

Light Drab.—

Cane marl	30 parts
Ball clay	24 parts
Feldspar	7 parts

Sage Body.—

Cane marl	15 parts
Ball clay	15 parts
China clay	5 parts
Stained with turquoise stain.

Colored Glazes For Pottery:

Blue.—

White glaze	100 parts
Oxide of cobalt	3 parts
Red lead	10 parts
Flowing blue	3 parts
Enamel blue	3 parts

Grind.

Pink.—

White glaze	100 parts
Red lead	8 parts
Marone pink U. G.	8 parts
Enamel red	3 parts

Grind.

Buff.—

White glaze	100 parts
Red lead	10 parts
Buff color	8 parts

Grind.

Ivory.—

White glaze	100 parts
Red lead	8 parts
Enamel amber	8 parts
Yellow underglaze	2 parts

Grind.

Turquoise.—

White glaze	100 parts
Red lead	10 parts
Carbonate of soda	5 parts
Enamel blue	4 parts
Malachite, 110	4 parts

Grind.

Yellow.—

I.—	White glaze	100 parts
	Red lead	10 parts
	Oxide of uranium	8 parts
	Grind.
II.—	Dried flint	5 parts
	Cornwall stone	15 parts
	Litharge	50 parts
	Yellow underglaze	4 parts
	Grind.

Green.—

I.—	Oxide of copper	8 parts
	Flint of glass	3 parts
	Flint	1 part
	Red lead	6 parts
	Grind, then take:
	Of above	1 part
	White glaze	6 parts
	Or stronger as required.
II.—	Red lead	60 parts
	Stone	24 parts
	Flint	12 parts
	Flint glass	12 parts
	China clay	3 parts
	Calcined oxide of copper	14 parts
	Oxide of cobalt	1/4 part
	Grind only.

Green Glaze, Best.—

III.—	Stone	80 parts
	Flint	8 parts
	Soda crystals	4 parts
	Borax	3 1/2 parts
	Niter	2 parts
	Whiting	2 parts
	Oxide of cobalt	1/4 part
	Glost fire, then take:
	Above frit	60 parts
	Red lead	57 parts
	Calcined oxide of copper	5 1/4 parts

Black.—

Red lead	24 parts
Raddle	4 parts
Manganese	4 parts
Flint	2 parts
Oxide of cobalt	2 parts
Carbonate of cobalt	2 parts

Glost fire.

White Glazes:

China.

I.—	Stone	6 parts
	Niter	2 parts
	Borax	12 parts
	Flint	4 parts
	Pearl ash	2 parts
	To mill:
	Frit	24 parts
	Stone	15 1/2 parts
	Flint	6 1/2 parts
	White lead	31 parts
II.—Frit:
	Stone	24 parts
	Borax	53 parts
	Lynn sand	40 parts
	Feldspar	32 parts
	Paris white	16 parts
	To mill:
	Frit	90 parts
	Stone	30 parts
	White lead	90 parts
	Flint	4 parts
	Glass	2 parts
III.—Frit:
	Stone	50 parts
	Borax	40 parts
	Flint	30 parts
	Flint glass	30 parts
	Pearl barytes	10 parts
	To mill:
	Frit	160 parts
	Red lead	30 parts
	Enamel blue	1/2 part
	Flint glass	2 parts
IV.—Frit:
	Borax	100 parts
	China clay	55 parts
	Whiting	60 parts
	Feldspar	75 parts
	To mill:
	Frit	200 parts
	China clay	16 parts
	White clay	3 1/2 parts
	Stone	3 parts
	Flint	2 parts
V.—Frit:
	Stone	40 parts
	Flint	25 parts
	Niter	10 parts
	Borax	20 parts
	White lead	10 parts
	Flint glass	40 parts
	To mill:
	Frit	145 parts
	Stone	56 parts
	Borax	16 parts
	Flint	15 parts
	Red lead	60 parts
	Flint glass	8 parts

Earthenware.

I.—	Flint	108 parts
	China clay	45 parts
	Paris white	60 parts
	Borax	80 parts
	Soda crystals	30 parts
	To mill:
	Frit	270 parts
	Flint	20 parts
	Paris white	15 parts
	Stone	80 parts
	White lead	65 parts
II.—Frit:
	Flint	62 parts
	China clay	30 parts
	Paris white	38 parts
	Boracic acid	48 parts
	Soda crystals	26 parts
	To mill:
	Frit	230 parts
	Stone	160 parts
	Flint	60 parts
	Lead	120 parts
III.—Frit:
	Stone	56 parts
	Paris white	55 parts
	Flint	60 parts
	China clay	20 parts
	Borax	120 parts
	Soda crystals	15 parts
	To mill:
	Frit	212 parts
	Stone	130 parts
	Flint	50 parts
	Lead	110 parts
	Stain as required.
IV.—Frit:
	Stone	100 parts
	Flint	44 parts
	Paris white	46 parts
	Borax	70 parts
	Niter	10 parts
	To mill:
	Frit	200 parts
	Stone	60 parts
	Lead	80 parts

Pearl White Glaze.

Flint	50 parts
Stone	100 parts
Paris white	20 parts
Borax	60 parts
Soda crystals	20 parts
To mill:
Frit	178 pounds
Lead	55 pounds
Stain	3 ounces

Opaque Glaze.

Borax	74 parts
Stone	94 parts
Flint	30 parts
China clay	22 parts
Pearl ash	5 1/2 parts
To mill:
Frit	175 parts
Lead	46 parts
Flint	10 parts
Oxide of tin	12 parts
Flint glass	12 parts

Glaze For Granite.

I.—	Stone	100 parts
	Flint	80 parts
	China clay	30 parts
	Paris white	30 parts
	Feldspar	40 parts
	Soda crystals	40 parts
	Borax	80 parts
	To mill:
	Frit	360 parts
	Flint	50 parts
	Stone	50 parts
	Lead	80 parts
II.—Frit:
	Borax	100 parts
	Stone	50 parts
	Flint	50 parts
	Paris white	40 parts
	China clay	20 parts
	To mill:
	Frit	210 parts
	Stone	104 parts
	Flint	64 parts
	Lead	95 parts

Raw Glazes.

I.—	White lead	160 parts
	Borax	32 parts
	Stone	48 parts
	Flint	52 parts
	Stain with blue and grind.
II.—	White lead	80 parts
	Litharge	60 parts
	Boracic acid	40 parts
	Stone	45 parts
	Flint	50 parts
	Treat as foregoing.
III.—	White lead	100 parts
	Borax	4 parts
	Flint	11 parts
	Cornwall stone	50 parts
IV.—	Red lead	80 parts
	Litharge	60 parts
	Tincal	40 parts
	Stone	40 parts
	Flint	52 parts

Rockingham Glazes.

I.—	Litharge	50 parts
	Stone	7 1/2 parts
	Red marl	3 parts
	Oxide of manganese	5 parts
	Red oxide of iron	1 part
II.—	White lead	30 parts
	Stone	3 parts
	Flint	9 parts
	Red marl	3 parts
	Manganese	5 parts
III.—	Red lead	20 parts
	Stone	3 parts
	Flint	2 parts
	China clay	2 parts
	Manganese	3 parts
	Red oxide of iron	1 part

Stoneware Bodies.—

Ball clay	14 parts
China clay	10 parts
Stone	8 parts
Ball clay	8 parts
China clay	5 parts
Flint	3 parts
Stone	4 parts
Ball clay	14 parts
China clay	11 parts
Flint	4 parts
Stone	5 parts
Feldspar	4 parts
Cane marl	16 parts
China clay	10 parts
Stone	9 parts
Flint	5 parts

Glazes.

Stone	10 parts
Flint	5 parts
Whiting	1 1/2 parts
Red lead	10 parts

Hard glaze:

Feldspar	25 parts
Flint	5 parts
Red lead	15 parts
Plaster	1 part

Softer:

White lead	13 parts
Flint glass	10 parts
Feldspar	18 parts
Stone	3 parts
Whiting	1 1/2 parts

Best:

Feldspar	20 parts
Flint glass	14 parts
White lead	14 parts
Stone	3 parts
Oxide of zinc	3 parts
Whiting	1 1/2 parts
Plaster	1 part

Rockingham Bodies.—

Ball clay	20 parts
China clay	13 parts
Flint	7 parts
Stone	1 part
Cane marl	22 parts
China clay	15 parts
Flint	8 parts
Feldspar	1 part

Glazes.—

I.—	Red lead	60 parts
	Stone	8 parts
	Red clay	3 parts
	Best manganese	5 parts
II.—	White lead	60 parts
	Feldspar	6 parts
	Flint	16 parts
	Red clay	6 parts
	Manganese	12 parts
III.—	Red lead	100 parts
	Stone	15 parts
	Flint	10 parts
	China clay	10 parts
	Manganese	40 parts
	Crocus martis	2 parts
IV.—	Litharge	100 parts
	Feldspar	14 parts
	China clay	20 parts
	Manganese	40 parts
	Oxide of iron	2 parts

Jet.

When fired use the following:

Glaze.—

Stone	60 parts
Flint	30 parts
Paris white	7 1/2 parts
Red lead	140 parts

One part mazarine blue stain to 10 parts glaze.

Mazarine Blue Stain.—

Oxide of cobalt	10 parts
Paris white	9 parts
Sulphate barytes	1 part

Calcine.

Another Process Body.—

Ball clay	16 parts
China clay	12 parts
Flint clay	9 parts
Stone clay	6 parts
Black stain	7 parts

Glaze.—

Litharge	70 parts
Paris white	3 parts
Flint	12 parts
Stone	30 parts
Black stain	20 parts

Black Stain.—

Chromate of iron	12 parts
Oxide of nickel	2 parts
Oxide of tin	2 parts
Carbonate of cobalt	5 parts
Oxide of manganese	2 parts

Calcine and grind.

Blue Stains.—

I.—	Oxide of cobalt	2 1/2 parts
	Oxide of zinc	7 1/2 parts
	Stone	7 1/2 parts
	Fire this very hard.
II.—	Zinc	6 pounds
	Flint	4 pounds
	China clay	4 pounds
	Oxide of cobalt	5 ounces
	Hard fire.
III.—	Whiting	3 3/4 parts
	Flint	3 3/4 parts
	Oxide of cobalt	2 1/2 parts

Glost fire.

Turquoise Stain.—

Prepared cobalt	1 1/2 parts
Oxide of zinc	6 parts
China clay	6 parts
Carbonate of soda.	1 part

Hard fire.

Materials:

Tin Ash.—

Old lead	4 parts
Grain tin	2 parts

Melt in an iron ladle, and pour out in water, then spread on a dish, and calcine in glost oven with plenty of air.

Oxide Of Tin.—

Granulated tin	5 pounds
Niter	1/2 pound

Put on saucers and fire in glost oven.

Oxide Of Chrome

Potash	6 parts
Flowers of sulphur	1 part

Put in saggar, inside kiln, so that fumes are carried away, and place 4 or 5 pieces of red-hot iron on the top so as to ignite it. Leave about 12 hours, then pound very fine, and put in saggar again. Calcine in hard place of biscuit oven. Wash this until the water is quite clear, and dry for use.

Production Of Luster Colors On Porcelain And Glazed Pottery.

Metallic Luster On Pottery.

Metallic Glazes On Enamels.

	Arab	Italian
Copper sulphide	26.87	24.74
Silver sulphide	1.15	1.03
Mercury sulphide	—	24.74
Red ocher	71.98	49.49

These were ground with vinegar and applied with the brush to the already baked enamel. A great variety of iridescent and metallic tones can be obtained by one or the other, or a mixture of the following formulas:

	I	II	III	IV	V	VI
Copper carbonate	30	—	—	28	—	95
Copper oxalate	—	—	—	—	5	—
Copper sulphide	—	20	—	—	—	—
Silver carbonate	—	3	—	2	1	5
Bismuth subnitrate	—	12	—	—	10	—
Stannous oxide	—	—	25	—	—	—
Red ocher	70	85	55	70	84	—

Silver chloride and yellow ocher may be respectively substituted for silver carbonate and red ocher. The ingredients, ground with a little gum tragacanth and water, are applied with a brush to enamels melting about 1814° F., and are furnaced at 1202° F. in a reducing atmosphere. After cooling the ferruginous deposit is rubbed off, and the colors thus brought out.

Sulphur, free or combined, is not necessary, cinnabar has no action, ocher may be dispensed with, and any organic gummy matter may be used instead of vinegar, and broom is not needed in the furnace. The intensity and tone of the iridescence depend on the duration of the reduction, and the nature of the enamel. Enamels containing a coloring base—copper, iron, antimony, nickel—especially in presence of tin, give the best results.

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How To Tell Pottery And Porcelain.