ATTACHING THE FOOT.Fig. 4
With great care and much taste pieces can be pinched and welded together into delightful forms, best shown in the refinements of the Cha Noya pottery of Japan. This pinching must be done carefully and above all sympathetically. To those that know or feel the possibilities of the clay it will respond readily. Much more taste and judgement is required in the making of a really satisfactory pinched shape, than is needed in forming one with coils. Square, polyhedral, or irregular shapes other than circular may bestuck upor pieced together in the following manner: Upon a table nail two strips of wood one quarter of an inch thick, ten or twelveinches apart. Sprinkle between the strips with flint or fine sand and batter out some soft clay thereon. Scrape the surplus clay off with a straight-edge and then roll the clay between the strips flat with a rolling pin. Upon this thin slab mark out the sides, base, top, etc., of the shape to be built. Run a thin knife round each shape, but do not cut quite down to the table. Cut along the inside edge of each strip to allow the whole slab to contract evenly and allow it to toughen slightly. Carefully remove and reverse the slab and separate the pieces, being careful not to distort the shapes in the process.
The shape must be stuck up before the pieces become brittle or too stiff to bend. Roughen each opposing edge and moisten with slip, that is, clay mixed with water to the consistency of thick cream.
Press the edges firmly together and weld well each joint with soft clay. (Fig. 5.) This operation should be most thorough, as any weak joint will inevitably open when fired. Lids should be cut slightly largerthan the shapes they have to fit and sandpapered true when dry. Sharp edges and angles should be smoothed with the fingers before the shape gets hard.
“STICKING UP†FLAT-SIDED POT.Fig. 5
The chief pitfall to avoid in this process is a hard wooden look. The ductile plastic qualities of the clay should be remembered and such additions as feet or handles should emphasize this important point.
Finally, the careful sympathetic craftsman, with infinite patience, by utilizing all three methods, can build vessels of almost any shape,—square, round, elliptical, banded, strapped, bossed, fluted, and embellished with handles, spouts, and feet. Ancient and mediæval pottery is rich in such forms.
TOOLS FOR CLAY WORK.
Moulding, Casting, and Pressing
“Our soundes is good, Our shapes is neat,Its Davis cast us so compleat.â€
“Our soundes is good, Our shapes is neat,Its Davis cast us so compleat.â€
—From an old bell at Stoke Rivers.
The casting process, employed so extensively in commercial work, is in its essence mechanical and therefore can never have the spontaneity or character of thrown work. To-day when the thrower and turner with hand and eye trained for good shapes is rare indeed, it is often the only method by which the student can obtain large shapes of high finish for painting or glazing in transparent colours.
In the process the shape is first designed andcarefully drawn on paper, allowance being made for the shrinkage of the finished pot which may be as much as 1 in 6 with some kinds of slip. It should be refined in profile with no returns that may bind or hold in the mould when drying, yet it is obvious that simple shapes that can be built or thrown by the beginner are not suitable for casting.
MANDREL, ROLLED IN PAPER.Fig. 6
“ONE PIECE†MOULD FOR BOWL—METHOD OF RELEASING ORIGINAL.Fig. 7
The shape correctly drawn, a mandrel, a steel tapering to a point, the butt wormed to screw on a lathe, and long enough to give some play at either end, is rolled in stout paper, gummed at the edges, as in Fig. 6. This is removed and allowed to set, thus giving a paper shell just fitting the mandrel. Trim this square at the base and stick it uprightby means of a piece of clay on a well-oiled portion of a table. Around this as a centre is fitted a roll of linoleum, oiled inside and secured with string, with all its joints caulked with clay. The inside diameter of this cylinder should be about1â„2†larger than the greatest diameter of the drawn shape. Enough superfine plaster to fill this is now mixed. To do this shake plaster by handfuls into a bowl of water until it appears to refuse more, pour off any surplus water, and stir with a wooden ladle or the hand, avoiding air bubbles.
A TWO-PIECE MOULD.Fig. 8
POURING IN PLASTER.Fig. 9
A little practice in casting plaster bats will give the experience necessary for mixing plaster. When well mixed and a slight thickening is perceptible, it is poured very carefully into the cylinder, the paper shell being kept upright in the centre. (Fig. 9.) In about 20 minutes the surface of the plaster will feel warm. It is now set and the linoleum is removed. The plaster cylinder, when dry, is fitted on the mandrel, and this screwed to the lathe head. Two or three chisels are now required. (Fig. 10.) The rest on the lathe is clamped in a convenient position and a cutting chisel held as shown (Fig. 11), cutting edge up. The cylinder is revolved briskly as indicated by arrow, and the shape is roughly hollowed out. Proceed gradually until the shape begins to emerge, taking care not to cut too deeply. (Fig. 12.) Towards the finish use the calipers frequently to check the measurements.At top and bottom about1â„2†waste is left (Fig. 13 A), turned straight, the actual line of top and base being slightly grooved in the plaster. The form may be pretty accurately finished with the chisels and then nicely smoothed with sandpaper. For this process the rotary movement is reversed.
TURNING TOOL.
CHISEL POINTS.Fig. 10
POSITION OF TOOL.Fig. 11
The shape is now removed from the lathe and is ready for moulding.
With a kick wheel having a removable head the mandrel can be screwed on and the block turneddown in an upright position. The difficulty of steadying the tool renders this method somewhat unsuitable for this process, where perfect symmetry and a high finish are required. The plaster should not be so dense for turning on the wheel or the kicking is apt to become very arduous and this tends to dislocate the set of the spindle. One of the best of ways is to draw a quantity of shapes, cast their blocks, and turn them on a hired lathe, preferably run by power.
PARTLY TURNED BLOCK ON LATHE.Fig. 12
The finished shape is now well lathered with parting or stopping. This is made by boiling 1 lb. soft soap,1â„4lb. Russian tallow, and a small piece of soda. Another stopping is made by dissolving 1 lb. soft soap in 1 qt. water and stirring in1â„4pt. paraffin oil. Several coatings may be necessary to imparta waxy surface. When no longer absorbent, it is dried and slightly polished with a bit of cotton waste. At the finish the form should be clean, smooth, glossy, and non-absorbent.
With simple shapes, as in Figs. 7 and 8, a one-piece or a two-piece mould can be made, and here the bottom waste is not necessary, but with any return or foot a three-piece mould will be required. The waxed shape is now divided perpendicularly exactly in half, by a pencil line. (A, Fig. 13.) It is then laid on its side and bedded in clay up to the pencil lines, the clay being sloped slightly down from the marks. (F, Fig. 13.) Box in now with well-soaped boards tight against top and bottom but allowing about 11â„2†at sides. Wipe the shape over with waste dipped in olive oil but leave no surplus oil on the surface. Plaster well mixed as before is poured in until about 11â„2†to 2†above the greatest projection of the shape, great care being taken to avoid or dislodge air bubbles. (B, Fig. 13.)
When the plaster is set but still warm, the shape is removed and the side of the plaster that rested on the clay trimmed flat and several joggles or natches are made. (C, Fig. 13.) The shape is now replaced exactly as cast and the new surfaces treated with parting and the whole slightly filmed with oil as before. Great care must be used, for any oil on the actual surface of the mould spoils the suction of theplaster at that spot. Box in and then cast just as before. This gives two halves with waste top and bottom.
A: METHOD OF DIVIDING. B: MOULDING 1ST HALF. C: MOULDING 2ND HALF. D: A METHOD OF SECURING BOARDS. E: MOULDING BASE. F: MOULDING 1ST HALF.Fig. 13
The shape is now placed on the lathe and the bottom waste turned off, the base of the shape being slightly hollowed. The creator having arrived so far successfully may now unbend and scratch his mark on this new surface before well waxing it.
Dowels are cut in the waste of the two halves as shown, the fresh parts soaped, all fitted together and slightly oiled, then boxed in as in D and E, Fig. 13. Plaster about 2†thick at the thinnest part is poured on and the mould is complete. When set, the shape is removed and the three parts trimmed on all the outside edges. (Fig. 14.) The three pieces are assembled, firmly tied up to prevent warping, and thoroughly dried.
If preferred, the mould can be made cylindrical instead of square. This will give a more even suction to the slip and may be worth the extra trouble. For casting purposes a refractory clay containing a good percentage of China clay, maturing at about 03-01 but remaining perfectly white and porous, will be required.
Slip for casting is made thus: Clay, picked or broken into small pieces, is thrown into a bucket of warm water well slubbed up by hand and passed through a fine sieve (No. 80) with the aid of a stoutbrush and thinned to the consistency of thick cream. This should be matured for some days, frequently stirred, and again sieved before using. For very small or fragile shapes, a finer sieve (120) is advisable. The mould, quite dry and clean, is now slightly moistened with a scrupulously clean sponge and water, the parts assembled, corded, and firmly wedged, leaving the top free as in Fig. 15. The slip, thoroughly stirred, is poured in very gently to avoid bubbles. With awkward moulds, a tube or funnel should be used to prevent splashing. If the mould be placed on a whirler and turned to and fro, it will prevent the heavier matter in the slip settling too quickly.
THE THREE PARTS OF THE MOULD.Fig. 14
As the slip sinks in the mould, the subsidence being due to the absorption of the water by the plaster, the mould should be continually filled up. After a few minutes the mouth is scraped free to test the deposit. When this is thick enough, varying, of course, with the size of the shape, the slip is poured out into another bucket. An unorthodox but often useful trick for strengthening long necks is to slide a piece of glass over the mouth and reverse the mould for a minute or so. The neck full of slip thus allows a slight extra deposit on the part that most needs it when we come to finishing off the lip.
MOULD READY FOR SLIP.Fig. 15
FREEING TOP.Fig. 16
Let the mould drain a little over the slip bucket and then reverse to dryslowly. When the wet look has disappeared from the surface of the slip, scrape the top free and run a knife around to prevent sticking as the shape contracts. (Fig. 16.) In a few hours it will be dry enough to permit of the sides being eased off and the shape left to dry on the base. (Fig. 17.) When tough enough to handle with safety, the waste and cast lines are trimmed and finished off, any air bubbles or holes broken down and filled with clay scraped from the waste or base. If this finishing is left until the shape be dry, it is impossible to hide such defects. The greatest care must be exercised in handling cast shapes, as they are exceptionally fragile.
SHAPE READY FOR TRIMMING.Fig. 17
When quite dry, the whole form should be carefully gone over with a very fine sandpaper. A superfine surface should be imparted by rubbing with the hands. When using transparent glazes, as with under-glaze painting, it is essential that all scratchesbe removed, and especially must all sharp edges be eliminated on neck or shoulder, for the glaze running away from these places imparts a hideously cheap look to what otherwise may be a fine shape. All these points having received attention, the date is scratched on the bottom of the shape and it is now ready to biscuit.
Generally speaking, it will be found that slip the consistency of cream is right for casting, possibly thicker for big open shapes, and after the right proportion is settled it is as well to test what it weighs to the pint.
As will be readily seen, this process, whilst open to many objections, lends itself to shapes that are refined and delicate and to those that have flutings or raised ornament. Such decorations, or the spouts of jugs, may be modelled in wax on the plaster shape before casting and appear in reverse on the mould. Designs may be scratched on the mould or shape and show as a delicate tracery beneath the glaze. All these things, however, add to the difficulty of casting and should be approached by degrees and with restraint. For in unskilled hands the process lends itself to soulless and mechanical repetition.
Pressing
Moulds having moderately wide mouths enable the potter to press his shapes instead of cast them.This method in expert hands is even quicker than casting and has the advantage of imparting a sturdier look to large shapes. Pressing is also resorted to for those shapes to which it would be difficult for the slip to obtain free access.
ROLLING OUT CLAY.Fig. 18
For the ordinary three-piece mould the procedure would be thus: The clay, well wedged and quite plastic, is rolled out as described in Jigger and Jolley work, to a suitable thickness. (Fig. 18.) Butter cloth or fine linen will do instead of leather to roll the clay on. The insides of the three parts of the mould are sponged and pieces of the thin rolled clay roughly cut to fit them. These pieces are now fitted and well applied to the three parts by dabbing with the damp sponge. A soft close-textured sponge, or a soft felt dabber, is best for this operation. Whenclosely setting, the edges are trimmed and given a slight bevel. The top is cut straight. Then the mould is assembled and firmly tied. Some of the waste clay is rolled into thinropes. With the bevelled edges slightly moistened, these ropes are firmly wedged into the two side junctions and round the base. Where the mouth is large enough for the insertion of the hand this is not a difficult operation. If it be narrow, the two halves of the mould may be tied up and the joints welded together before they are assembled on the base. A coil of clay can then be placed on the edge of the base just clear of the two sides which are now fitted over and tied up. Then a stick sponge is used to join up the base to the sides. (Fig. 19.) After a little while the shape is fit to be removed and is finished in the usual way.
Nothing can rival large thrown shapes for vigour or variety, but unfortunately they are not always within reach of even the good craftsman. Then this method offers the least objectionable substitute for them and in clever hands is capable of many fine results.
The following method is used to mould handles or simple applied ornament. Handles, feet, masks, etc., are usually pressed and stuck on the dry shape with slip. To mould them some skill is necessary if the press is to be quite accurate and free from twist or ugly seams.
SECTION OF A MOULD. STICK-SPONGE WELDING BASE TO SIDES.Fig. 19
One way, when the handle or foot is symmetrical, is to cut the model exactly in half. This must be done when the model is tough enough to handle without bending or distorting it. One half is laid cut side down upon a sheet of glass, and surrounded at a convenient distance with clay walls. Plasteris now poured on to form one half of the mould, and allowed to set. It is then removed and the smooth surface joggled and claywashed (brushed over with claywater). The other half is then very carefully applied to the half still embedded in the mould, the walls built round and the other part of the mould cast. Then all is trimmed up and a groove run round the form as shown. (Fig. 20.) For pressing, the form is well filled with clay and the two halves of the mould strongly pressed together. Any surplus clay will squeeze into the groove and when tough enough to remove the whole is “fettled†and finished before drying and sticking up.
HALF OF MOULD FOR PRESSING HANDLE.Fig. 20
With care and practice this method is possible: Build walls and pour in enough plaster to form one half of the mould. Before it stiffens, very carefully press in the handle or ornament just up to the halfway line and allow to set. Joggle, claywash, and cast the second half. Finally, when the object is of any size, clay walls may be used as described in the chapter on Figurines.
Jigger and Jolley Work
“Earth I am, et is most trwe, desdan me not, for so ar you.â€â€”From an old platter.
“Earth I am, et is most trwe, desdan me not, for so ar you.â€
“Earth I am, et is most trwe, desdan me not, for so ar you.â€
—From an old platter.
Dishes, platters, and to some extent bowls, are usually made on aJigger and Jolley. The jigger has a revolving head, fitted to receive moulds. The jolley has a pivoted arm to which different profiles may be clamped. In factories these things are complicated and go by power, but in a studio where the output of platters and dishes is likely to be limited something simple will do. Where the wheel is strong, well-hung, and fitted with a removable head, a contrivance as shown at Fig. 21 can be fitted by any carpenter, that should serve all purposes.
The vertical supports of the jolley arm should be quite rigid. The arm itself must so pivot that the face of any profile screwed onto it will cross the head of the jigger, or wheel if one be used, through the centre. In other words, the cutting profile must form a diagonal of the circular head. Then, too, it must be hung at a height sufficient to allow a fairly thick block of plaster being used for a mould.
MAKING A DISH.Fig. 21
When making these moulds, the slotted wheelhead or the jigger head is removed and soaped or oiled. Then a circular block of plaster is cast to fit. This may be done with the aid of a roll of linoleum, much in the way described in casting. The paper cone will, of course, be replaced by the wheel head, bedded face up in clay. This plaster block has to be moulded to the exact size of the dish or plaque required. To do this a profile of zinc is necessary. The true section of the dish is drawn full size, and profiles giving one half of the back and front are traced on a stout sheet of zinc. The zinc is roughly cut to shape with shears and then finished with a file to a chisel edge (see cut). The two profiles are then firmly backed with shaped wooden forms, slotted to screw onto the arm of the jolley. Theprofile giving thefaceof the plaque is securely adjusted in a horizontal position, the inner point, giving the centre of the platter, being exactly over the centre of the jigger head. The plaster block, which should be turned down before it sets hard, is shipped back into position, the jigger revolved and the profile gradually pressed down until the true section is obtained,i.e.when the profile is exactly horizontal again. The mould is now removed, trimmed at the sides if necessary, and set apart to dry. It is then ready to use. The mould is slipped into position and revolved to insure even rotation. Then the profile giving the back of the platter screwed onto the arm and both adjusted until the stop allows the profile to rest at just that distance from the mould required by the thickness of the platter. (Fig. 22.)
PROFILE IN POSITION ABOVE PLATE MOULD.Fig. 22
The arm is then swung clear of the mould, which is well sponged with water to receive the clay. This is carefully wedged and then rolled out or batted flat on a piece of leather until it is a little thicker than the thickest part of the platter (see Fig. 23). The slab so made is smoothed with a palette knife, taken up, leather and all, slapped onto the mould, clay side down, and the leather removed. The clay is now well dabbed down with a wet sponge or dabber, to take out all wrinkles, pressed firmly onto the mould and the waste cut off.
CUTTING EDGE OF PROFILE.Fig. 23
Now the jigger or head is set spinning, the jolley pulled over it, and the profile gently pressed into the clay. Water is used freely to prevent the profile sticking, and as it becomes clogged the clay is removed. The turning is continued until the profile comes to a stop on the rest. Holes that may appear should be filled up before the finish, at which time the surface should present a smooth unscratched appearance. The shape is allowed to dry on the mould until tough enough to be slipped face down onto a perfectly flat slab dusted with fine sand or flint to preventsticking. In this position it is left to dry, when the edges are nicely trimmed with fine sandpaper.
For bowls the process is similar, but the mould here gives the outside and the profile the inside as in cut. (Fig. 24.) If made on the outside, they split before they can be removed. With small bowls the clay is wedged and a lump pressed into the mould by hand. With large bowls requiring a deep foot this must be turned separately and stuck on after the bowl is removed from the mould.
BOWL.Fig. 24
Where a jigger and jolley is not available, plates and bowls may be duplicated as follows: Place the plate bottom up on a well-soaped surface or a piece of glass. Should the plate not lie quite flat, caulk the apertures with clay, then all round and distant one and one half inches from the rim, build clay walls, or fix a containing band of linoleum, of sufficient height to allow plaster being poured in an inch and a half above the base or foot of the model. Mix fairly stiff plaster and pour in. Let it set, and then remove walls and the model. This gives a mould of the reverse of the plate or bowl. The mould isthoroughly dried before using and then sponged with clean water. Clay of the desired thickness is then rolled out as described and applied to the mould and dabbed flat with a sponge or dabber. The finish is imparted with the fingers and the surplus at edges trimmed with a knife. When tough, the press is slipped out and reversed to dry on a piece of sanded glass. Where there is a rim to the plate or bowl, this should be filled in cleanly with clay before the whole is pressed. It is of course impossible to mould thus bowls that possess a deep or under-cut foot.
PLATE MOULDED TO GIVE BACK.Fig. 25
MOULD. TO GIVE FACE OF PLATE.Fig. 26
THE KICK WHEEL.
ANCIENT EGYPTIAN POTTER.Egypt. B.C. 2000
Thrown Shapes
“The lyf so short, the craft so longe to learne.â€â€”Chaucer.
—Chaucer.
The wheel is the true fountain head of all beautiful shapes, and the student who would become a potter cannot get “on the wheel†too soon. Throwing, sometimesspinning, is the term applied to the making of shapes on the wheel. Interesting and really fine pots may be built or cast, but the ultimate appeal rests with the thrown shape.
Unfortunately, a complete mastery of throwing is not to be gained by a few spasmodic wrestles with the wheel. It comes only with long hours of concentrated effort. Having watched an accomplishedthrower and seen the full round shapes rise so easily between his dexterous fingers, it is with a severe shock that one realizes at the first attempt the skill and practice that will be required before such a desirable proficiency is attained.
The best kind of wheel is the kick wheel shown in the illustration. With this the feet, hands, and head work in harmony, accelerating or retarding the motions as required. It is a not distant relation of the earliest wheel, which was a heavy head on a short shaft, pivoted in a stone socket. Set spinning by hand, it was kept revolving some time by its own momentum. This form of wheel is used even to this day in the near and far East.
Its first development was a secondary wheel and driving band turned by hand. This led to the wheel shown in the frontispiece and to the kick wheel and again on to the factory wheel. This in its turn is being superseded by the steam wheel, which gears onto a running band, the foot being used to start, stop, and regulate the speed. The two last named were introduced with the idea of accelerating the production rather than the improvement of the shapes. No doubt the now primitive kick wheel, much as used by the potters of the Renaissance, will be found good enough for us.
The tools required for throwing, after the wheel itself is secured, are as follows: a thin copper wiretwisted between two bits of wood, a pricker, a fine soft sponge, another bit of sponge tied to a stick, one or two modelling tools and a rib (see Fig. 27).
THROWING & SHAVING TOOLS.Fig. 27—1, “Ribâ€; 2, Modelling Tools; 3, Pricker; 4, Sponge; 5, Wire; 6, 7, and 8, Shaving Tools; 9, Leather.
The clay is first knocked up into shape ready for the throwing. To do this it iswedged, a fair-sized piece being taken in both hands and thrown violently down on the bench, cut across, and smashed together again. This process is repeated until all air bubbles are expelled. This is ascertained by cutting with a wire. The finger is then passed across the surface to tell if it is well together, andnot hard and soft in streaks. If, as must happen in a small pottery, the clay is out of condition, it is best remedied by cutting it with the wire into thin slabs, piling them criss-cross and then wedging the mass. If still streaky, it can be quickly tempered, piece by piece. A double handful is torn across, wedged together at a different angle between the hands, re-torn, and re-wedged, until hard and soft are welded indistinguishably together.
This thorough wedging is essential, as with beginners a small lump or bubble will usually be sufficient to bring about the collapse of the shape.
The clay being thoroughly wedged is rolled into balls of a convenient size. For first practice they should be on the small side and moderately tough, as this allows a little more play before the ball becomes too soft. The wheel is now started revolving from right to left (see cut). The head being clean, the ball is thrown smartly onto its centre. The hands are now wetted in a bowl of water, which is put, together with the tools, on the shelf to the right. Then gently but firmly, with hands placed as shown in Fig. 28, the ball is centred. At this stage, perhaps the most critical of all, the wheel should revolve quite briskly. The hands should be moistened if inclined to stick and the left hand held steady, the elbow pressed into the side, the forearm hard on the rest. The right hand has morefreedom and coaxes the ball into a half sphere. This when dead centred is elongated, pressed down again, and re-formed into a truncated cone. The left hand still steadying, the thumb of the right is pressed firmly into the centre of the top, down and out, to hollow the ball (see page18), but stopping short of the lathe head. At this stage the most convenient shape to form is a cylinder, its walls gradually diminishing upwards with a little fatness at the rim. To do this the wheel is slowed down a little and the fingers of the left hand inserted. The sides are felt and gently pulled up, between the left index finger and the two first fingers of the right hand, gradually higher and thinner, always endeavouringto keep the walls at an even but slightly tapering thickness. (Fig. 29.)
CENTRING.Fig. 28
PULLING UP.Fig. 29
At first two fingers only will be inserted, but as the shapes grow in size the whole of the left hand will gain admittance. Then the perfect cylinder may be modified to almost any required form. With narrow-mouthed shapes the opening must be kept as small as possible, for the clay once pulled out it is difficult if not impossible to compress it again. The centring and hollowing once mastered, the chief difficulties to avoid are getting the bottom of the walls too thin before the top is pulled up, and making the top wavy and irregular. If the latter happens, it should be at once cut back with thepricker, which is also used to test the thickness of the sides and base.
When the shape has been pulled up to the required form and is sufficiently thin, the top is smoothed and fattened between the fingers. This not only imparts a look of substance to the vase and takes away anycastlook, but gives strength where it is most needed. The inside, if wet, can be cleaned out with the stick sponge and the outside lightly smoothed with the other sponge. For the insides of bowls or wide-mouthed shapes, a rib of slate or zinc (see Fig. 30) will be useful for obliterating ridges. The last operation is to pass the wire, held firmly to the wheel head, beneath the pot and lift it off and place it on one of the pot boards or plaster discs. (Fig. 32.)
“RIB†OF METAL FOR OUTSIDE. “RIB†OF SLATE OR BONE FOR INSIDE.Fig. 30
The first primitive forms are far better left frankly for what they are. Afterwards when bigger and more finished shapes are attempted, they can be thinned and refined with the aid of the rib and a modelling tool, a considerable finish being put onbefore they are removed from the wheel. With bowls or large shapes it will be found impossible to lift them off without destroying the shape in some degree. For these wood or plaster discs will be required. The plaster bats need soaking in water before use and the wood must be three-ply to prevent warping. These discs are centred on and firmly stuck to a layer of clay run out on the wheel head, and when the pot is finished they are removed with it.
FINISHING WITH “RIBâ€.Fig. 31
PASSING WIRE UNDER TO REMOVE.Fig. 32
All this sounds very simple, but the beginner will do well first to practise and master centringthe ball. Until this be done, the rest of the work is worthless. After this must be practised the pulling up, the pressing down, and the forming of truncated cones, then hollowing the ball and pulling up into a cylinder. A true cylinder accomplished, it is easy to branch out into simple wide-mouthed vase forms. As the skill increases, shapes with double curves and long or narrow necks may eventually be achieved. Throwing to a set copy induces a necessary concentration at this stage, but once a mastery is attained, shapes seem to suggest themselves.
A small mirror placed so as to reflect the true form will be found of great service. When pairs or several duplicates are required, a drawing of the exact profile must be made and a “rib,†of zinc or slate, filed to fit. Without such a guide the matching up is well-nigh impossible.
STAGES FROM CENTRED BALL TO TURNED SHAPE.Fig. 33
When watching a clever thrower in a factory making some difficult and probably horrible vase, it isintensely interesting to see the fine forms evolved in the process. To the artist the impulse to stop him is almost irresistible. It was there that the old masters showed their wisdom and restraint. They stopped at the right moment and none of their shapes descend to the merely clever.
There is a nobility about a large vase lacking in a small one. Once the appetite be whetted for big pots the desire for size seems insatiable. The only way out, except for the born thrower, is the two- or three-piece vase.
The Chinese were masters of this as of every other process and we find that they frequently made vases of quite moderate size in two or three parts, sticking the pieces together with consummate skill. This process, however, should never be attempted until considerable proficiency has been gained in throwing to a drawing, for in any but expert hands it is doomed to failure. The shape must be carefully drawn out on paper and the sections marked off and then thrown exactly to size. Any deviation means endless trouble, with eventual disappointment.
For this difficult work the student unable to devote a lifetime to throwing will find a removable wheel head a necessity. Then a slotted one can be screwed on which will allow a plaster disc to be shipped back into exactly the same position, thus saving the difficult task of re-centring. For prolongedoperations these plaster discs require to be shellacked to prevent the work leaving.
ASSEMBLY OF THE PARTS.Fig. 34
To start with a shape as shown in the illustration might be attempted. (Fig. 34.) The drawing made full size is hung in full view. Then the gauge is set tothe exact width of the joint. The bottom half is first made, being cut square and true with the pricker. The drawing is reversed and the upper half thrown, the neck being at the bottom with a fair amount of waste beneath. When each part is trimmed accurately to measure, they are put aside to toughen.
The top portion will stiffen just as required, leaving the neck still moist. The bottom half will need watching to prevent the upper edge drying before the base gets firm enough to support the top when attached. A damp cloth lightly wrapped round it will help to insure the ideal condition for sticking up, which is a gradually diminishing state of toughness from the base up to lip, the junction of the parts being in exactly the same state.
When fit to handle, the top half is cut through at the lip, allowing a trifle for finishing off. Next the bottom half, still firmly fixed to the bat, is slotted back into its original position on the wheel. The flat surfaces that have to be applied and stuck are now very carefully and slightly roughened, then painted with thick slip made from the same body. These two wet edges are now applied and gently and firmly pressed into position, the wheel being slowly revolved to see if the two halves run true. When well together and apparently sticking, a little wedge of soft clay can be carefully run in all around the joint. This operation should be verythorough, and the clay wedge must be carefully welded into the sides of the joint. This is finished off on the outside with the rib and the inside very lightly smoothed with the fingers. During this process the top should be covered with a soft wet cloth, then when the joint has been made good and will stand the slight strain, the lip is finished off in the ordinary way. With three-pieced shapes the lip can be finished before sticking up, as the last part is thrown in its right position. If at any time the shape shows a disposition to leave the plaster bat, it should be stuck down with wet clay. The toughened shape can now be turned down in its upright position, cut off the bat, and the base hollowed in a chuck (see next chapter).
POTTER AT WHEEL.India. B.C. 2000
Turning or Shaving
“A sharp spear needs no polish.â€â€”Zulu proverb.
—Zulu proverb.
The turning or shaving operation takes place when the green shape has dried to aleatherycondition. It consists in shaving the sides and hollowing the base until the thickness is uniform. The shape is thus made much lighter and rendered less liable to crack from unequal contraction. At the same time a fine finish is imparted to the surface.
One of the handiest tools for shaving is shown in Fig. 27, no. 6, but a piece of hoop iron bent at right angles and shaped with a file will serve. Small hollows can be finished with a modelling tool. An old piece of leather will close up and finish the surface. In factories a horizontal lathe is usually employed, the shape being fitted over achumorchuck. Skilled men can turn shapes down until they are scarcely thicker than tin, but this, it is needless to add, is an abuse of method even with porcelain, and quite out of place with stoneware or earthenware. All that is necessary is to trim the thick sides, hollow the base, and smooth the surface. (Fig. 35.)
SECTION SHEWING TURNED & THROWN WALL OF A SHAPE.Fig. 35
A simple way to arrive at this is to throw on the wheel a chuck of stiff clay to fit the shape, wide-mouthed ones being fitted over and ordinary shapes within the chuck. (Figs. 36 and 37.) A piece of soft linen is placed over this chuck to prevent sticking and the shape fitted and centred. When spinning quite truly from right to left and steadied with the left hand, the tool should be gently applied as shown in the illustration. Hollow the base and then shave the sides, turning all down very gradually and improve the outline as much as possible in the process.