Pottery, for Artists, Craftsmen & Teachers

CHAPTER XVI

Chapter 166,112 wordsPublic domain

THE EDUCATIONAL VALUE OF POTTERY

"The principal point in Education is that one's knowledge of the World begins at the right End."

--SCHOPENHAUER.

The study of the fictile art of the potter, even from the theoretical side alone, cannot fail to quicken and broaden education. The antiquity of the craft, stimulating research amongst the records of ancient civilizations, brings to light customs and habits bearing very closely upon the earliest struggles of man to emancipate himself from mere brute surroundings. The primitive decorations rudely scratched on clay vessels antedate and forecast the hieroglyphic and sign languages of all nations.

It would be but hyperbole to claim that without clay the Mosaic tablets would have remained unwritten, but indubitably the clay cylinders of Assyria gave a strong impulse to the development of ciphering and writing and the spread of learning,--an impetus not to be derived from the obstinate granite medium so generally employed by the Egyptians.

It is this amenable ductile quality, so easily receptive of the most emotional touch, that has made and still makes clay such an admirable medium of expression for the young,--whether young in the history of the world or young in actual years. And this malleability is accompanied by a tenacity that permits slow building up, remodelling, and high finish, suitable to work of the most painstaking character. To this is added the fixed, unalterable quality imparted by fire, so that pottery more than any other craft preserves an imperishable record of the ages.

This positive chronicle is valuable alike to the savant or the student. Indeed the most trivial child's toys of the Hellenes, the quaint water pots of the Peruvian peasant, or the unassuming tea bowl of the esoteric followers of Riku may chance to convey to the sincere student a clearer idea of the habits and thoughts of their producers than many a pedantic treatise or translation.

"So lively shines In them Divine resemblance and such grace The hand that made them on their shape hath poured."

--MILTON.

Coming down to points in close contact with the curricula of schools, we all subscribe to the dictum of Ruskin that "Everyone, from the King's son downwards, should learn to do something finely and thoroughly with his hands." What then more suitable than sympathetic clay wherein to fashion the first fancies of the child mind. It is a medium at once attractive and easy to mould, giving a tangibility and reality to forms and things that can never be obtained by drawing or painting. Then the limitless uses to which clay is put, and, with the development of hygiene, increasingly will be put, have the closest bearing upon the everyday life of the child. They are intimately connected with other studies that cannot fail to be rendered more attractive by working in clay.

But clay work is a branch now so universal that it seems unnecessary to dwell upon its advantages to the kindergartener.

The valuable remedial effects of clay work upon the defective are perhaps less widely known. The manipulation induces a most beneficial concentration and provides a fine discipline without a trace of inimical restraint. Turning to higher grades, the use of clays should foster an interest in the formation, composition, and disintegration of rocks, and in the properties of the products so engendered; in short, a liking for geology.

With the making of simple glazes and colours will awaken an intelligent curiosity concerning the nature of minerals and metals, their actions and reactions in the fire; a lively sympathy only awaiting a touch to turn it into a love for chemistry and physics. Then as power and ambition and craftsmanship develop, there must needs be a study of the history of ornament. This impinges too closely upon history and geography to fail to increase the student's attraction towards these more remote but allied fields.

Finally, is it not in the realm of æsthetics that there looms the ultimate reward? The proper pursuit of pottery must eventually lead us "towards that idealization of daily life ... and the road that connects the love of the beautiful with the love of the good is short and smooth" (President Eliot). In the hurried curricula of to-day art plays a rather sorry part. Little time indeed is left for contemplation, for the realization of all that beauty and harmony in our surroundings may mean to us in our everyday work.

The making of a bowl, with the concentration required to shape it in a manner at once beautiful and serviceable, must quicken the perception of beauty and sharpen the quality of judgement, not only for things fictile, but in far wider fields. Thus the things of everyday contact--the tableware, the chairs, the doors, the windows, pictures, ornaments, hangings, and fittings--will all come in for intelligent scrutiny and criticism. This in turn will be carried on and over into matters civic. This must result in a careful estimation, selection, and appreciation of our surroundings, bringing them into harmony with our cultivated thoughts and so enabling us to get through the day's work with the least amount of useless friction and with the greatest possible measure of enjoyment, well-being, and well-doing.

APPENDIX I

THE EQUIPMENT

The divinity that presides over potting is an expensive as well as an exacting mistress. The equipment of even a small pottery is, unfortunately, a matter of considerable expense. Try it from whatever angle we may there is the cost of the kiln to be faced, besides a host of other small but cumulative expenses. The first essential is, of course, a roomy workshop with if possible a top as well as a side light. If the craftsman means business, he should remember that the initial cost of a kiln is often in inverse ratio to its upkeep. If he would aspire to big things, full-bellied pots, plaques, reliefs, and figures,--and every craftsman would,--a brick kiln will be wanted. One holding a dozen saggars could be built, but where some experience has been obtained with materials and processes, a larger one would be more economical. With oil or gas kilns of the ordinary school size the cost of firing and the extra time is proportionately too great to permit of any but comparatively high-priced pots being turned out. This may serve in some cases, but usually it is not practical potting where a livelihood has to be obtained. Where only the painting is to be fired on, an oil or gas kiln is exactly what is wanted.

In this appendix is given a plan of a workshop that has all the equipment necessary for the whole-hearted pursuit of the craft. In such an one a good craftsman, capable of modelling and painting decently a figure or a panel, a good thrower, and a handy boy could work wonders. They would be capable of turning out a surprisingly wide range of "pots": jugs, mugs, pots, bottles, bowls, buttons, dishes, plaques, panels, vases, tiles, and statuettes,--useful and beautiful things. Anything in fact worth doing can be done except fine tableware or those articles that by their nature demand more mechanical accuracy than is possible, or even desirable, for a craftsman to exhibit. Where much plaster turning for moulds was attempted, a lathe would be required; ordinarily the hiring of one should be practicable and expedient. Where only built or cast shapes were attempted, the wheel and its long years of drill might be dispensed with, and it is possible, with strong individual work of high finish and fine quality and the consequently restricted output, that an oil or gas kiln would give economically practicable results. Between the kiln for firing decoration simply painted on the ready-made shape to the full equipment here described will be found several modifications, but to try the craft without a kiln of some sort is an imbecile proceeding.

Small brick kiln supplied with saggars. Small muffle kiln--oil or gas--for over-glaze and lustres. Small enameller's kiln for firing quick trials. Kick wheel, and tools for throwing. Clay bin, zinc-lined. Damp-box. Drying cupboard. Plaster bin. Pot boards and brackets. Table, strong and heavy. Clay: white, red, buff. Plaster. Glaze materials. Oxides, lustres. Under- and over-glaze colours. Modelling tools, callipers. Painter's outfit. Brushes, straight-edges. Shellac, beeswax, French chalk. Gum arabic and tragacanth. Glaze tubs, teak. Sieves, glaze and slip, Nos. 80, 100, 120. Buckets. Bowls, enamelled and earthenware. Small porcelain ball mill, hand or power. Spray and pump (respirator). Small outfit for carpentry. Files, sheet iron, and zinc, wire and cutters, cords, sandpaper. Benches and shelves ad lib., odd cupboards, chairs, etc., Shovels and slicer for firing, tongs for trials. Two large tubs and rubber tubing. Sand and flint. Spurs, props, fire tiles. Tile boxes. Disc (emery) for grinding. Small pestle and mortar. Jugs and funnel. Potter's knife, sponges. Whirler. Turning tools and lathe. Temperature indicators. Oil can, oil, waste. Callipers and compass, rulers.

Most of this equipment has been previously described and needs no further comment.

The pot boards and brackets are simple but indispensable devices. The boards are about six feet long, iron shod or cross battened to prevent warping, and six or nine inches in width. The brackets of any serviceable kind are fixed to the wall at convenient distances. When throwing, turning, or glazing, the pots are stood on one of these boards to dry, and each board as filled is slipped onto the brackets. Thus the pots may be carried about to the kiln, drying cupboard, or glaze tubs without loss of time or frequent handling.

The table must be stout enough to withstand the heavy work of wedging and should have a top of hard wood. Teak or hard-wood glaze tubs have the advantage of not breaking either themselves or pots accidentally knocked against them. Further, some glazes stick badly to porcelain or enamel tubs.

EQUIPMENT FOR A SMALL POTTERY

In the small pottery plotted here, the equipment and arrangement were as follows:

An anthracite stove with the pipe running into the large room warmed the workshop in winter, but no wet or half-dry pots were left where the frost could get at them.

The glaze materials, oxides, colours, painting paraphernalia, finished pots, trials, and trial kiln were in the small room. The wheel had a good top and side light.

The drying cupboard, plaster bin, and moulds were at the end nearest the stove; the clay bin, damp-box, and sink farthest away.

All the walls were copiously supplied with brackets and shelves and handy benches.

Outside, in a well-built lean-to, was the muffle kiln for onglaze and lustre decoration.

This was well bracketed and shelved for the biscuit, and here was done the glazing, handy for packing in the brick kiln just outside. This was protected from the weather and other lean-to's held the saggars, coke, and coal.

EQUIPMENT FOR SCHOOLS

The teacher with ample funds and a free hand will find the previous chapter all-sufficient, but in many cases the purchase of a kiln will nearly exhaust the allowance and the rest of the equipment becomes sketchy.

The indispensable appliances are as follows:

A kiln, with fire tiles or shelves, props, spurs, and stilts, etc., for packing. A good clay bin and sieve for slip (No. 80) with a tub and two pails.

Scales and weights, pestle and mortar and glaze lawn (No. 100), shot for weights.

Plaster, for drying bats and working discs.

Large drip pan and three round pans.

Several jugs and bowls.

Spoons (wooden), knives, and big brushes.

Oil, gum, boards, strips, rolling pin.

Hammer, saw, iron straight-edge, sponges.

Glass slab and muller, palette knife and brushes for painting.

An atomizer or spray pump.

Glaze materials:

Kaolin, China stone, flint, silver sand, whiting, felspar, borax. A supply of ground pitchers and grog, cones.

Metallic oxides:

Tin, white, oxide of, iron, copper, manganese, cobalt, etc.

Under-glaze colours to taste.

Glass jars with lids to contain materials. Gummed labels, India ink.

For a school in the country or where ground is available, a kiln like the one shown at p. 164 should be practicable. It costs very little to build or to fire. Next comes the question of the clay. This is one of the most abundant of nature's materials, and almost any river bank or creek will supply clay of some kind. Any sort of clay near to hand should be thoroughly tested before going to other or distant sources.

The clay should be dried, then broken up with a hammer, and mixed with water, and the resultant "slurry" passed through a sieve (No. 80). The slip is allowed to settle and the water siphoned off. The thick slip is then dried on the plaster bats until stiff enough to work up between the hands. From this clay a tile, a plate, and a vase should be made and fired. If the pieces stand a fire of about 1100° (cone .03) without buckling, splitting, or crumbling, the clay should do quite well for school work. Possibly when screened fine enough for working, the clay may be too rich or _long_ and will split at a moderate fire. Then the screenings might be pounded in the mortar, passed through the sieve, and added to the slip. Again, ground pitchers, fine grog, kaolin, or calcined flint could be tried as stiffening agents. In the unlikely event of the clay being too refractory or _short_, a portion of rich, fusible, or _fat_ clay might be added, or the addition of powdered spar tested. (See chapter on Clays.) The colour of the body will hardly matter for schools; indeed a brown, red, or cane-coloured clay will give better results than a staring white paste, when working out simple school problems.

Where necessary, tin glaze could be used for a white ground, or an engobe; that is, a dip of white clay slip over the coloured body. For glazing, a leadless glaze is strongly to be advised. Lead is often indispensable to the craftsman, and with care need not become a danger; but in schools a lead glaze is positively harmful.

A glaze with a borax base, if ground dry and mixed with water and re-ground before sieving, will give little trouble if used immediately. It will answer for all grade work and may be used for spraying, dipping, pouring, or painting, with absolute safety.

The ground pitchers and grog may be obtained by pounding up broken biscuit and pieces of fire tile, respectively. This, and the glaze grinding, is, of course, laborious work, and suggests correlation with the Physical Education Department. The drip pan and the round tins make excellent moulds for casting drying bats and working bats.

For casting purposes plates and shallow bowls may be moulded in one piece as described, p. 26. If no lathe be handy, glazed vases may be used as substitutes, the "waste" being added in plasticine to the neck and base.

For tile-making, strips nailed on a stout board will serve in place of tile boxes. The clay is rolled out on cheesecloth with a rolling pin. Various other expedients for drying cupboards, damp-box, etc., will suggest themselves as the course develops.

The above equipment need not be very costly. With it the students should be capable of producing all kinds of tiles, built, pressed, and cast shapes, decorated in relief, with inlays or in colours or glaze.

SIMPLE RAW GLAZES. COLOURLESS

All the above colourless glaze masses may be coloured with combinations of the various metallic oxides, or from 3 to 7 or even 10 per cent of glaze stains or under-glaze colours.

APPENDIX II

GLOSSARY

=Alumina, or Oxide of Aluminium=, is one of the most abundant of earths. Combined with silica it is the chief constituent of kaolins and China clays. It imparts refractory qualities to clays and is an indispensable ingredient of pure glazes. Pure alumina or calcined Aluminium is a chemical product.

=Ammonia.=--A volatile gaseous matter, found in some clays. Alkaline in action.

=Antimony.=--A silver-white metallic element, used with other oxides as a colourant or to give opacity in glazes.

=Arsenic.=--A non-metallic volatile element, used in glaze making.

=Barytes.=--A heavy spar used with clays to introduce density and vitrescence.

=Bauxite.=--A very aluminous earth, used in preparation of pure alumina and to render clays refractory.

=Boracic Acid.=--The natural and, usually, impure product (boric acid being free from chemicals).

=Borax.=--The combined chemical product of soda and boracic acid. Used as a strong flux in glazes.

=Calcined Bones.=--The residuum of burned bones, used to stiffen artificial porcelain.

=Calcined Kaolin.=--Kaolin after it has been subjected to heat to drive off the water combined with it.

=Calcium Carbonate (Whiting).=--Found as a white rock, and ground to pure powder. Used with clays for soft bodies. Gives durability to glazes.

=Calcium Oxide (Lime).=--A widely distributed earthy matter. Imparts fusibility to clays, in nearly all of which it is present in varying proportions.

=Chrome, Oxide of.=--Used in making greens, browns, and blacks. Stands a high fire.

CLAYS:

=Ball Clay.=--Blue and black. Very plastic clays. Used with non-plastic materials, such as flint, stone, felspar, or whiting, to form fine earthenwares.

=Cane and Red Clays.=--Clays coloured by the presence of ferric oxide, and used extensively for bricks, terra-cotta tiles, and common pottery.

=China Clay.=--A yellowish-white, non-vitreous clay, product of the decomposition of granitic or felspathic rocks. Cornish China clay is exceptionally white, pure, and plastic. It is widely used with China, or Cornwall stone and calcined bones, to make bone porcelain. Felspar is added to render it vitreous. Mixed with ball clays, pipe clays, flint, and stone, it makes the various classes of earthen and stone wares.

=Pipe Clay.=--A very white, smooth clay. Less plastic than ball clays. Much used for making slips, engobes, and enamels.

=Saggar Clays or Fire Clays.=--Coarse refractory clays strengthened by the addition of grog, used for saggars, fire tiles, and bricks.

=Cobalt Oxide.=--The oxide of the steel-grey hard metal. Extremely valuable in pottery, making all shades of blue for under-glaze printing or staining. With iron or copper gives blue-greens.

=Copper, Oxides of, and Carbonate.=--Red, green, and black oxides of copper have been of the utmost value to potters. They are used to produce green, blue, turquoise, red, and crimson. Its extraordinary changes in reducing or oxidizing fires are of the greatest interest to the experimenter.

=Cornish or China Stone.=--A rock composed of felspar and quartz. Its vitrification (about 1400° C.) imparts hardness and density to China clays. It is a valuable constituent of glazes. First known as "moorstone" or "growan."

=Earthy Colourants.=--Rarely used in modern commercial pottery, except for salt-glazed jars, crocks, and peasant pottery.

=Felspar.=--A fusible rock found almost pure or in combination with potash and soda, the greater the percentage of alkalies the more fusible being the spar. It is used to replace more refractory materials in clay and to stiffen glazes.

=Flint.=--A pure silica with slight traces of calcium. Found in pebble form on seashores. Calcined and ground to a white powder, it is widely used to impart whiteness and strength to clays. Invaluable for bedding and packing in kilns. Used with the fluxes,--lead, borax, potash, and soda,--to make glazes and glass.

=Fluorspar.=--A combination of fluorine and calcium, more fusible than felspar, and of a white colour, felspar being pink.

=Galena.=--Lead sulphide, a highly poisonous material used on "peasant" pottery, giving a soft, yellowish, transparent glaze.

=Gold.=--Used in solution for delicate purples and lustres.

=Gypsum.=--When calcined gypsum becomes plaster of Paris, these two materials, together with the allied marble, limestone, and alabaster, are widely used in pastes (such as Parian), slips, engobes, and variously to impart fusibility or colour properties to glazes.

=Iron, Oxides of.=--Have a wide range of colour, from yellow to purple. They are used to stain glazes and colour bodies. They impart fusibility to clays and are carefully excluded from fine white bodies.

=Kaolin.=--A fine, white, very pure, and infusible China clay, almost pure alumina and silica. Chiefly used in the manufacture of porcelain and fine earthenware.

=Lead (Oxides and Carbonates of). White Lead, Red Lead, Litharge.=--Are very widely used as a safe and cheap flux. Poisonous. It cannot be used in those glazes that have to stand a high fire.

=Lime.= (_See_ =Calcium=.)

=Lynn Sand.= (_See_ =Quartz Sand=.)

=Magnesia.=--A white metallic element present in small quantities in most clays.

=Manganese.=--The black and brown oxides of this hard metal are much used to stain slips and bodies, and to colour glazes brown or purple.

=Marls.=--Amorphous deposits of lime, sand, and clay, very coarse in texture. Used in making saggars, drain pipes, and similar appliances.

=Nickel.=--A hard metallic element, the oxides of which are found useful in preparing blacks, greys, and greens.

=Nitre or Potassium Nitrate, or Saltpetre.=--A vitreous and aqueous compound, used in some glazes.

=Plaster of Paris.= (_See_ =Gypsum=.)

=Potash.=--Potassium carbonate or the leached ashes of plants. Used from earliest times as a powerful alkaline flux.

=Potash, Bichromate of.=--Used for pinks and crystalline effects. Poisonous.

=Quartz or Quartz Sand.=--Like Lynn or silver sand. This mineral is pure silica and free from lime, although the sands may contain some small percentage of iron. Used much like flint for bedding or with alkaline fluxes for the finest glazes.

=Rutile. Oxide of Titanium.=--Used variously to impart a yellow tinge to porcelain, and colour and irregularity to some glazes.

=Salt.=--Sodium chloride. Sometimes used in glazes, but best known in connection with salt glazing. It vaporizes at about 1200° C., forming a silicate or hard, thin skin of glaze over the clay.

=Silica.=--A hard, colourless crystalline element; found pure, as in quartz, or in combination with alumina and alkalies, as in all clays. Present in all glazes.

=Soda. Sodium Carbonate.=--Product of the decomposition of salts with acids. It is a strong alkaline flux and much used in glaze and glass-making.

=Silver Sand.= (_See_ =Quartz=.)

=Tin, Oxide of.=--Used from the earliest times to impart opacity to glazes.

=Tincal.= (_See_ =Borax=.)

=Titanium.= (_See_ =Rutile=.)

=Whitening.= (_See_ =Lime=.)

=Zinc, Oxide of.=--A white metallic oxide; used to brighten and stabilize glazes and colours.

POTTER'S TERMS

=Bags.=--Chimneys or walls of fire bricks built to protect the ware from flame.

=Baitings.=--The feed of fuel during firing.

=Bat.=--Any flat slab of plaster, biscuit, or fire clay.

=Biscuit.=--The fired but unglazed clay.

=Blowing.=--The shattering of the clay shape when biscuiting. Usually due to hurried firing or the sudden access of heat, and the consequent generation of steam.

=Blunger.=--A machine for mixing clay.

=Bungs.=--Piles of filled saggars.

=Chuck or Chum.=--The cone or cap used to support shapes during turning on the lathe.

=Clamming.=--The wet marl, sand, or siftings applied to cracks in the hatches or doors of kilns to retain the heat during firing.

=Craze.=--The minute cracks that appear in a badly fitting glaze. When arrived at by design, as in some Chinese work, it is termed a crackle, but there is then no fissure.

=Drawing.=--Unpacking the kiln after firing.

=Engobe.=--A dip or outer covering of slip; usually applied to inferior bodies to improve their appearance.

=Fat.=--Clays that are sticky or greasy are sometimes termed fat by potters.

=Fettle.=--To touch up, and remove traces of seams, cast lines, etc.

=Fluxes.=--Those materials which by their addition to paste or glaze render them fusible, although they may not always be fusible themselves.

=Glost.=--The glazed ware, usually applied to the glaze in firing, as glost-oven.

=Green.=--The clay shapes before biscuiting.

=Jigger.=--The wheel on which shapes are moulded with the aid of a jolley or profile.

=Joggle.=--The natch or key in a mould to insure correct adjustment and prevent slipping.

=Lawn.=--The fine mesh gauze through which glazes are strained.

=Long.=--A clay is termed long if very ductile and tenacious.

=Muffle.=--Usually the fire-clay box or interior of a small kiln, but applied to any kiln to the inside of which the flames have no access.

=Natch.= (_See_ =Joggle=.)

=Oxidizing.=--The ordinary method of firing gives an atmosphere in which there is always sufficient oxygen to consume all the carbon or combustible gases. If oxygen is present in excess, it causes reactions known as oxidizing.

=Pitchers.=--Finely ground biscuit. Added to some clays to increase refractories or porosity. Moulds made in such clays and fired are termed pitcher moulds.

=Potsherds.=--Any broken biscuit or pot, sometimes used for pitchers.

=Potting.=--A colloquialism used to designate the ceramic industry.

=Pugging.=--The roll of infusible clay placed between each saggar when building bungs.

=Reducing.=--The reaction that accompanies the introduction of smoke or gas containing carbon in a very finely divided state into a kiln during the process of firing glaze. Reduction is now widely employed in obtaining fine lustre effects.

=Refractory.=--Hard, infusible.

=Rich.=--Used of clays that are long and fusible, such as red clays.

=Riffle.=--A grooved and toothed plaster tool of steel.

=Saggars.=--Or seggers. The fire-clay receptacles in which the glazed ware is set during the firing.

=Setters.=--Supports used when packing friable biscuit.

=Short.=--A word used to denote a clay that crumbles or is difficult to pull up on the wheel.

=Sieve.=--Sometimes called a lawn, more correctly a screen for clay or slip.

=Slip.=--The sieved clay or paste in creamy liquid condition as used for slip decoration, engobes, or casting.

=Slub or Slurry.=--Clay mixed with water but not sieved, as with slip.

=Spy.=--The small hole, kept plugged, through which tests and cones are observed.

=Stunt.=--Or dunt. To crack or split on cooling.

=Turning.=--The shaving down of the clay shape on a lathe, to impart lightness and finish.

=U. G.=--Under-glaze (applied to colours).

=Vent.=--A hole to aid the even distribution of fire in a kiln or to accelerate the cooling off.

=Waster.=--Commercially, a spoiled pot; defective ones are termed "seconds."

=Wedging.=--The beating or slamming operation usually employed to expel air or correct inequalities just before clay is used by the thrower.

=Whirler.=--A circular support pivoting on its centre, used in casting or banding; similar to a banding wheel, but usually heavier.

MATERIALS, TERMS, ETC.

C = COMBINING WEIGHT E = EQUIVALENT WEIGHT ------------------------------------------------+------+-------------- SYMBOL |C OR E| FUSING POINT ------------------------------------------------+------+-------------- Alumina (calcined) Al_{2}O_{3} |C 102}|Very infusible Alumina (hydrated) Al_{2}O_{3}·3H_{2}O |C 156}| Aluminium Al |E 27 |627° C. Ammonia NH_{3} | |Volatile Antimony Sb |E 120 |432° C. Antimony oxide SbO | | Arsenic As |E 75 |500° C. Barium (metallic Ba |E 137 |Fuses above element) | | red heat Barium carbonate BaCO_{3} |C 197 | Barytes BaSO_{4} |C 233 |Fuses about | | white heat Bauxite | | Bismuth Bi |E 28 | Borax (crystals) Na_{2}B_{4}O_{7}·10H_{2}O |C 382 |Very fusible Boric acid (crystals) B_2O_3·3H_2O |C 124 | Boric acid (dry) B_2O_{3} |C 70 |High fusing Boron (metallic B |E 11 | point element) | | Calcined bones | |Infusible Calcined kaolin} Al_2O_3 · 2SiO_{2} |C 222 |Very infusible China clay (fine)} | | slightly | | vitreous | | at highest | | fire Calcium oxide (lime) CaO |C 56 |Very refractory | | if alone | | but fusible | | with clays Calcium carbonate CaCO_{3} |C 100 | China stone} 8SiO_{2}·2Al_{2}O_{3}·K_{2}O| 1379 |1300° C. about Cornish stone} | | Chrome oxide Cr_{2}O_{3} |C 79 | Chromium Ca |E 51 |Above platinum Cobalt Co |E 59 |1500° C. Cobalt oxide Co_{2}O_{3} |C 165 | Cobalt oxide (black) Co_{2}O_{4} |C 240 | Copper Cu |E 63 |1054°-1084° C. Copper oxide (black) CuO |C 79.5| Earthy colourants | | Ochres | | Siennas | | Umbers | | Felspar 6SiO_{2}·Al_{2}O_{3}·K_{2}O |C 556 |1200°-1300° C. | | about, | | according | | to purity Flint (calcined) SiO_{2} |C 60 |1830° C. about Fluorspar CaF_{2} | |Much lower | | than felspar Galena (lead sulphide) PbS | |Very fusible Gold Au |E 147 |1054°-1075° C. Gypsum (plaster of | | Paris, if calcined) CaSO_{4}·2H_{2}O |C 172 | Iron Fe |E 56 |1530°-1600° C. | | about Iron oxide Fe_{2}O_{3} |C 160 | Iridium Ir |E 193 |1950° C. about Kaolin (see calcined | | kaolin) Al_{2}O_{3}·2SiO_{2}·2H_{2}O|C 258 |Infusible Lead (metal) Pb |E 206 |326° C. Lead carbonate PbCO_{2} | | Lead, red oxide of Pb_{3}CO_{4} | | Lime (see calcium oxide | | or carbonate) CaO | | Lynn sand (see silver | | sand) SiO_{2} | | Magnesia (calcined) MgO |C 40 |430° C. Magnesia (carbonate) MgO·CO_{2} | | Manganese, carbonate MnCO_{3} |C 115 | Manganese (metal) Mn |E 55 |1670° C. about Manganese oxide (or | | black) MnO_{2} |C 87 | Nickel (metal) Ni |E 58 |1427°-1450° C. Nickel oxide NiO |C 75 | Nitre KNO_{3} | | Pearl ash or potash KOH | | Plaster of Paris | | (calcined gypsum) CaSO_{4}·1/2H_{2}O |C 145 | Platinum Pt |E 197 |1710°-1775° C. Potash, bichromate of K_{2}Cr_{2}O_{7} | |Fuses dull-red | | heat Potassium carbonate K_{2}CO_{3} |C 138 | Potassium oxide K_{2}O |C 94 | Quartz} SiO_{2} |C 60 |1830° C. about Quartz sand} | | Rutile (see titanium) | | Salt NaCl | |776° C. Silica SiO_{2} |C 60 | Silver sand (or quartz | | sand) SiO_{2} | | Silver (metal) Ag |E 107 |945°-962° C. Soda ash (calcined) Na_{2}CO_{3} |C 106 | Soda crystals Na_{2}CO_{3}·10 H_{2}O |C 286 | Sodium oxide Na_{2}O |C 62 | Tincal (see borax) | | Tin (metal) Sn |E 119 |233° C. Tin oxide (white) SnO_{2} |C 150 | Titanium oxide (rutile) TiO_{2} | |Infusible Uranium (metal) U |E 239 |1800° C. about Uranium, oxide of U_{3}O_{8} | | Whitening (see lime | | carbonate) | | Zinc (metal) Zn |E 65 |443° C. Zinc oxide (white) ZnO |C 81 | ------------------------------------------------+------+--------------

SEGER CONES. (STANDARD CONES. ABOUT 10° HIGHER.)

NUMBERS. TURNING POINTS. COLOUR, ETC.

APPROXIMATE DEGREES OF COLOUR IN KILN CONE HEAT AT WHICH MATERIALS SUITABLE TO BE NUMBER CONE TURNS FIRED AT THESE TEMPERATURES OR BENDS (APPROXIMATE)

_Centigrade_

.022 600° Commences to .021 650° Soft enamel or over-glaze show colour .020 670° colours. .019 690° .018 710° Dull red .017 730° Enamels on metals. Fluxes .016 750° and lustres. .015 790° .014 815° .013 835° Very soft glazes and hard Red to cherry .012 855° enamel colours. Some .011 880° lustres. Gilding. .010 900° .09 920° .08 940° .07 960° Dull cherry to .06 980° Majolica glazes or coloured light cherry .05 1000° glazes and stanniferous .04 1020° or tin glazes. .03 1040° .02 1060° Earthenware glazes. Soft .01 1080° China glazes. 1 1100° Dark orange to 2 1120° Soft to hard or fine pale orange 3 1140° earthenware biscuit. 4 1160° 5 1180° Sèvres soft bisque. 6 1200° 7 1230° Vitreous ware. Granite ware. Yellowish white 8 1250° Salt glaze. Stoneware. 9 1280° English bone porcelain or 10 1300° China biscuit. White 11 1320° 12 1350° Intense white 13 1380° German & Chinese porcelain. 14 1410° Sèvres porcelain. 15 1430° Bluish white {16} 1460° {17} 1480° Copenhagen porcelain.

To convert temperatures:

Centigrade into Fahrenheit.--Divide by 5, multiply by 9, and add 32.

Fahrenheit into Centigrade.--Subtract 32, divide by 9, and multiply by 5.

MEASURES, WEIGHTS, ETC.

APOTHECARIES

1 grain = .0648 gramme. 20 grains = 1 scruple = 1.296 grammes. 3 scruples = 1 drachm = 3.888 grammes. 8 drachms = 1 ounce = 31.103 grammes.

TROY

1 grain = .0648 gramme. 24 grains = 1 pennyweight = 1.555 grammes. 20 pennyweights = 1 troy ounce = 31.1035 grammes.

AVOIRDUPOIS

16 drams = 1 ounce. 16 ounces = 1 pound. 14 pounds = 1 stone. 28 pounds = 1 quarter. 112 pounds = 1 hundredweight (cwt.). 20 hundredweight = 1 ton (2240 lbs.).

CAPACITY (WET)

1 gill = 1.42 decilitres. 4 gills = 1 pint = .568 litre. 2 pints = 1 quart = 1.136 litres. 4 quarts = 1 gallon = 4.545 litres. 2 gallons = 1 peck = 9.09 litres. 4 pecks = 1 bushel. 8 bushels = 1 quarter.

BOOKS OF REFERENCE

TECHNICAL Chemistry of Pottery. Langenbeck, Karl. Chemistry of Pottery. Shaw, Dr. S. Clays. Occurrences, Properties, and Uses. Ries. Colouring and Decorating of Ceramic Ware. Brongniart, A. Ceramic Technology. Binns, C. F. Notes on the Manufacture of Earthen Ware. Sandeman, E. A. Notes on Pottery Clays. Fairie, Jas. Pottery Decoration. Hainbach, R.

TECHNICAL AND HISTORICAL Leadless Decorative Tiles. Furnival, W. J. Faience and Mosaic, and other volumes. Furnival, W. J.

MANUAL Pottery. Lunn, Richard. Grand Feu Ceramics. D'oat, Taxile. The Potter's Craft. Binns, C. F. Practical Keramics for Students. Janvier, C. A.

HISTORICAL AND ARTISTIC Art of the Old English Potter. Solon, L. V. Chinese Porcelain. Gulland. Chinese Porcelain. Monkhouse, Cosmo. Ceramic Art in Great Britain. Jewitt, L. History of Pottery and Porcelain. Marryat. Majolica. Fortnum, C. D. E. Potters, Their Arts and Crafts. Sparkes and Gandy. Pottery and Porcelain in the United States (and other volumes). Barber. Persian Ceramic Art (and other volumes). Wallis, H. Illustrated catalogue of the Faience of Persia and Near East. Burlington Fine Arts Club.

APPLIANCES AND MATERIALS, ETC.

SOLD BY

BALL MILLS. Wengers, Ltd. Eng. (Hanley, Stoke on Trent.)

Abbey Engineering Co. 220 Broadway, N. Y. City, U. S. A.

BISCUIT SHAPES. Hirshberg Art Co. Baltimore, Md.

{CHINA AND BALL. Mandle and Sant. East Liverpool, Ohio, U. S. A.

{CHINA AND MODELING. Stewart & Co. N. Y. City, U. S. A.

CLAYS { Wengers. Hanley, Great Britain.

{MODELLING AND Western Stoneware Co. Monmouth, {STONEWARE Ill., U. S. A.

{SAGGAR AND STONEWARE. W. H. Cutter, Woodbridge, N. J., U. S. A.

CONES. Wengers, Ltd. Hanley, Eng.

Drackenfeld & Co. Murray St., N. Y. City, U. S. A.

Professor Ed. Orton. Columbus, Ohio.

GLAZES. Wengers, Ltd. Hanley, Eng.

Drackenfeld & Co. Murray St., N. Y. City, U. S. A.

Roessler, Haslacher Chemical Co. William St., N. Y. City, U. S. A.

KILNS. GAS. Fletcher, Russell. Warrington, Eng.

KILNS. GAS AND OIL. Bellevue Perfection. Detroit, Mich., U. S. A.

KILNS. OIL. Caulkins Revelation. Detroit, Mich., U. S. A.

KILNS. TRIAL. Wengers. Hanley, Eng.

LAWNS AND SIEVES. Drackenfeld & Co. 50 Murray St., N. Y. City.

A. Sartorious & Co. Murray St., N. Y. City.

Wengers. Hanley Staffs, Eng.

PLASTER. Wengers. Hanley, Eng.

Drackenfeld & Co. N. Y. City.

Calvin Thompkins. Battery Pl., N. Y. City.

QUARTZ, FLINT, FELSPAR. Wengers, Ltd. Hanley, Eng.

Drackenfeld & Co. Murray St., N. Y. City, U. S. A.

Golding & Sons. Trenton, N. J., U. S. A.

SCALES. Wengers. Hanley Staffs, Eng.

Hy. Troemner. Philadelphia, Pa., U. S. A.

STILTS, ETC. Trenton Stilt & Spur Co. Trenton, N. J., U. S. A.

Wengers. Hanley, Eng.

U. G. COLOURS, ETC. Wengers. Eng.

Drackenfeld & Co. N. Y. City, U. S. A.

WHEELS. Crossley Mfg. Co. Trenton, N. J., U. S. A.

T. S. Nickerson. Newburyport, Mass., U. S. A.

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TRANSCRIBER'S AMENDMENTS

Transcriber's Note: Blank pages have been deleted. On pages that remain, some unnecessary page numbers may have been deleted when they fall in the middle of lists. Some illustrations may have been moved. When the author's preference can be determined, we have rendered consistent on a per-word-pair basis the hyphenation or spacing of such pairs when repeated in the same grammatical context. The publisher's inadvertent omissions of important punctuation have been corrected.

The following list indicates any additional changes. The page number represents that of the original publication and applies in this etext except for illustrations since they may have been moved.

Page Change

20 the highest fire (around 17000°[1700°] Centigrade). 91 but it is [a] waste of time to attempt it 181 The slip is allowed to settled[settle] and the water siphoned off. 193 AL[Al]_2O_3 · 2SiO_{2} 193 Cobalt | C_{6}[Co] 194 Felspar |6SiO_{2}·Al_{2}O_{3}·K^{2}O[K_{2}O]

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