Part 31

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.»—Frit:

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

{170}

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.»—Frit:

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.»—Frit:

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.»—Frit:

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 {171} Flint 10 parts Oxide of tin 12 parts Flint glass 12 parts

«Glaze for Granite.»—Frit:

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.»—White:

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.»—Hard glaze:

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 {172}

«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.»—Procure some first-class red marl, add water, and, by passing through a fine lawn, make it into a slip, and dip the ware therein.

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» is made by mixing powdered bichromate of potash with sulphur as follows:

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.»—The luster colors are readily decomposed by acids and atmospheric influences, because they do not contain, in consequence of the low baking temperature, enough silicic acid to form resistive compounds. In order to attain this, G. Alefeld has patented a process according to which such compounds are added to the luster preparations as leave behind after the burning an acid which transforms the luster preparation into more resisting {173} compounds. In this connection the admixture of such bodies has been found advantageous, as they form phosphides with the metallic oxides of the lusters after the burning. These phosphides are especially fitted for the production of saturated resisting compounds, not only on account of their insolubility in water, but also on account of their colorings. Similarly titanic, molybdic, tungstic, and vanadic compounds may be produced. The metallic phosphates produced by the burning give a luster coating which, as regards gloss, is not inferior to the non-saturated metallic oxides, while it materially excels them in power of resistance. Since the lusters to be applied are used dissolved in essential oils, it is necessary to make the admixture of phosphoric substance also in a form soluble in essential oils. For the production of this admixture the respective chlorides, preeminently phosphoric chloride, are suitable. They are mixed with oil of lavender in the ratio of 1 to 5, and the resulting reaction product is added to the commercial metallic oxide luster, singly or in conjunction with precious metal preparations (glossy gold, silver, platinum, etc.) in the approximate proportion of 5 to 1. Then proceed as usual. Instead of the chlorides, nitrates and acetates, as well as any readily destructible organic compounds, may also be employed, which are entered into fusing rosin or rosinous liquids.

«Metallic Luster on Pottery.»—According to a process patented in Germany, a mixture is prepared from various natural or artificial varieties of ocher, to which 25–50 per cent of finely powdered more or less metalliferous or sulphurous coal is added. The mass treated in this manner is brought together in saggars with finely divided organic substances, such as sawdust, shavings, wood-wool, cut straw, etc., and subjected to feeble red heat. After the heating the material is taken out. The glazings now exhibit that thin but stable metallic color which is governed by the substances used. Besides coal, salts and oxides of silver, cobalt, cadmium, chrome iron, nickel, manganese, copper, or zinc may be employed. The color-giving layer is removed by washing or brushing, while the desired color is burned in and remains. In this manner handsome shades can be produced.

«Metallic Glazes on Enamels.»—The formulas used by the Arabs and their Italian successors are partly disclosed in manuscripts in the British and South Kensington Museums; two are given below:

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.

«To Toughen China.»—To toughen china or glass place the new article in cold water, bring to boil gradually, boil for 4 hours, and leave standing in the water till cool. Glass or china toughened in this way will never crack with hot water.

«How to Tell Pottery and Porcelain.»—The following simple test will serve: Hold the piece up to the light, and if it can be seen through—that is, if it is translucent—it is porcelain. Pottery is opaque, and not so hard and white as porcelain. The main differences in the manufacture of stoneware, earthenware, and porcelain are due to the ingredients used, to the way they are mixed, and to the degree of heat to which they are {174} subjected in firing. Most of the old English wares found in this country are pottery or semichina, although the term china is commonly applied to them all.

«Cheese»

«Manufacture.»—The process of cheese making is one which is eminently interesting and scientific, and which, in every gradation, depends on principles which chemistry has developed and illustrated. When a vegetable or mineral acid is added to milk, and heat applied, a coagulum is formed, which, when separated from the liquid portion, constitutes cheese. Neutral salts, earthy and metallic salts, sugar, and gum arabic, as well as some other substances, also produce the same effect; but that which answers the purpose best, and which is almost exclusively used by dairy farmers, is rennet, or the mucous membrane of the last stomach of the calf. Alkalies dissolve this curd at a boiling heat, and acids again precipitate it. The solubility of casein in milk is occasioned by the presence of the phosphates and other salts of the alkalies. In fresh milk these substances may be readily detected by the property it possesses of restoring the color of reddened litmus paper. The addition of an acid neutralizes the alkali, and so precipitates the curd in an insoluble state. The philosophy of cheese making is thus expounded by Liebig:

“The acid indispensable to the coagulation of milk is not added to the milk in the preparation of cheese, but it is formed in the milk at the expense of the milk-sugar present. A small quantity of water is left in contact with a small quantity of a calf’s stomach for a few hours, or for a night; the water absorbs so minute a portion of the mucous membrane as to be scarcely ponderable; this is mixed with milk; its state of transformation is communicated (and this is a most important circumstance) not to the cheese, but to the milk-sugar, the elements of which transpose themselves into lactic acid, which neutralizes the alkalies, and thus causes the separation of the cheese. By means of litmus paper the process may be followed and observed through all its stages; the alkaline reaction of the milk ceases as soon as the coagulation begins. If the cheese is not immediately separated from the whey, the formation of lactic acid continues, the fluid turns acid, and the cheese itself passes into a state of decomposition.

“When cheese-curd is kept in a cool place a series of transformation takes place, in consequence of which it assumes entirely new properties; it gradually becomes semi-transparent, and more or less soft, throughout the whole mass; it exhibits a feebly acid reaction, and develops the characteristic caseous odor. Fresh cheese is very sparingly soluble in water, but after having been left to itself for two or three years it becomes (especially if all the fat be previously removed) almost completely soluble in cold water, forming with it a solution which, like milk, is coagulated by the addition of the acetic or any mineral acid. The cheese, which whilst fresh is insoluble, returns during the maturation, or ripening, as it is called, to a state similar to that in which it originally existed in the milk. In those English, Dutch, and Swiss cheeses which are nearly inodorous, and in the superior kinds of French cheese, the casein of the milk is present in its unaltered state.

“The odor and flavor of the cheese is due to the decomposition of the butter; the non-volatile acids, the margaric and oleic acids, and the volatile butyric acid, capric and caproic acids are liberated in consequence of the decomposition of glycerine. Butyric acid imparts to cheese its characteristic caseous odor, and the differences in its pungency or aromatic flavor depend upon the proportion of free butyric, capric, and caproic acids present. In the cheese of certain dairies and districts, valerianic acid has been detected along with the other acids just referred to. Messrs Jljenjo and Laskowski found this acid in the cheese of Limbourg, and M. Bolard in that of Roquefort.

“The transition of the insoluble into soluble casein depends upon the decomposition of the phosphate of lime by the margaric acid of the butter; margarate of lime is formed, whilst the phosphoric acid combines with the casein, forming a compound soluble in water.

“The bad smell of inferior kinds of cheese, especially those called meager or poor cheeses, is caused by certain fetid products containing sulphur, and which are formed by the decomposition or putrefaction of the casein. The alteration which the butter undergoes (that is, in becoming rancid), or which occurs in the milk-sugar still present, being transmitted to the casein, changes both the composition of the latter substance and its nutritive qualities.

“The principal conditions for the preparation of the superior kinds of cheese {175} (other obvious circumstances being of course duly regarded) are a careful removal of the whey, which holds the milk-sugar in solution, and a low temperature during the maturation or ripening of the cheese.”