The following points highlight the four main steps followed for manufacturing pottery. The steps are: 1. Clay Preparation 2. Actual Shaping 3. Firing 4. Painting and Decorating.
Step # 1. Clay Preparation:
Clay preparation is an essential step in processing to prepare a pot. Alluvium of river banks or large lakes is often the most suitable material. Since the nature of the clay deposition in a river depends on the nature of rock and soil through which the river flows many alluvial deposits are not very suitable for the preparation of pots. In such areas even the clay needs special preparation. Usually clays rich in minerals and capable of forming an extremely fine grained homogeneity are the most suitable for giving shapes.
Thus, the clay used in the making of a pot can be of:
(a) Well levigated structure.
(b) Coarse grained structure, or at times deliberately mixed with external agencies like husk, powdered stone, sand, grass or hay or similar other material.
In this case the clay is identified as Tempered with whatever be the tempering material.
Step # 2. Actual Shaping:
The actual shaping of a pot can be done by two basic ways. It could be handmade or wheel-made. The handmade pots can be either made with coil of clay arrangement or using a mould. The prepared clay can be arranged in a coil to obtain the pot shape and then beaten with a flat wood from outside and absorbing the force on a stone pebble from the inside.
This beating releases large amount of clay surface to enable shaping a much bigger pot than the original clay coil. In another method a basket mould or the mould of a broken pot can be used to plaster clay from inside and then lift the finished shape out of the mould. Final finishing does require beating in the same manner as used for the coiled pots. All handmade pots lack the characteristic rows of circular lines noted in the modern pot surfaces.
In wheel made pottery prepared clay is put at the central region of a heavy wheel fixed on a pivoted fulcrum. The wheel is given rotatory motion first and then the mud is slowly pulled with the help of the thumb and the rest of the four fingers manipulating it. The centrifugal force on the mud in rotation helps to create a uniform circular shape.
All wheels made pottery can be identified by observing the fine lines of granular arrangement visible on the surface of the pot. As a rule almost all the wheel made pots can be made very thin and the thickness is uniform over the entire surface.
The wheel helps in completing a shape but the rest of the treatments are more time consuming and tedious. Normally the finished pot is further given thorough touch of frequently Wetted hands. This enables the small pores on the surface of the pot to be filled in and a generally shining surface appears. This treatment is called burnishing.
At times a mud and colour mixture is made and the pot is coated with this solution before allowing it to sun dry. This also renders closing all pores on the surface besides coating it with a desired colour. This treatment is called slipping. In some specific cases a pot may be first slipped in a light colour and then allowed to sun dry for an hour or so and then again dipped in another darker coloured slip.
Again it is allowed to dry for an hour or so. Then lightly scratched designs are executed on the surface in such a manner that the lower slip is exposed on the scratched lines. The design is finally made permanent by firing. This treatment is called reserved slipping. A colour wash can be given before or after firing and this forms yet another form of surface treatment.
Any pot surface which has been given no such treatment is usually referred to as matted surface. Often this can be further roughened by sticking wet hands on the surface and then lifting up the hand. Such surfaces are referred to as rusticated surfaces.
Step # 3. Firing:
The final texture of the pot, however, depends a great deal on firing. A smooth and uniform texture can be achieved only when there is an open hearth firing in the presence of uniformly controlled ventilation, a suitable media that burns gradually and a proper piling of the pots to be fired.
Uniform supply of air can be maintained by digging out air ducts from the bottom of the furnace. A regulated firing usually turns clay into brick red colour. If the temperature is not high enough it may cause blotchy appearance on the surface and at times even if the surface has uniformly turned red there will always be a core within the thickness of the clay which will remain gray.
It is only in adequately maintained temperature, duration and air circulation that the entire thickness of the clay turns red. We can, thus, distinguish an ill fired pot from a well fired one by looking into the results. There are two specific generic ceramic types known in prehistory which are mainly created by specially devised firing techniques.
(i) Painted Gray Ware of PGW are the ceramics which have been fired grey and then painted with black designs. The name chosen is highly misleading and can lead many beginners to think this as a type which is painted with grey colour. The grey color, it is believed, is obtained by firing thin clay pots to as high a temperature as 800°C. Such a high temperature can be achieved only in closed furnace with constant feeding of fuel and oxygen from the bottom.
(ii) Black-and-Red Ware or BRW is a very interesting variety of ceramics which is caused by a firing technique. These are completely black in the inside and around the rim on the outside. The rest of the outer surface is brick red. The rendering of the entire inside black led many an archaeologist to believe that this is the result of inverted firing in the absence of an adequate supply of oxygen.
Chemical studies of the scraped surface, however, show that the black colour (which is not only on the surface but extends half through the thickness – the rest half being red upto the outer surface) is caused by carbon. It is, therefore, concluded that the sun dried pot must have been given a coating of some organic resin, oil or some similar matter, before firing.
During firing this organic material on the surface as also the thickness through which it is absorbed, is burnt leaving the carbon free. Some authorities claim that double firing might have been required for this type of surface finish. It is important to note at this juncture that Black-and-Red Ware shapes are usually medium to small in size and never include large storage pots. In other words these seem to be only “tablewares” and hence may be given special treatments by the culture using them.
Step # 4. Painting and Decorating:
A pot may be painted before firing. These paintings are usually more permanent. Subsequent to firing the same painted designs may again be reinforced with another coat. In rare instances a special glaze may be given after the painting. This glaze is prepared by crushing tamarind seeds and cooking the powder in water.
This solution is colourless and when spread on a painted surface protects the paint in case it is done after firing and also renders the surface glazed like glass. Incised decorations are quite common in many prehistoric pots and this need to be done before firing. These may be simple nail depressions in a series or even horizontal lines scratched along the neck.
Sometimes small lumps of clay are fixed on the surface in order to decorate and these are referred to as applique bosses. A special kind of incised decoration appears in many advanced ceramics which is so uniform that it is believed that a pattern has been first engraved on a wooden wheel and then the wheel has been rotated with a moderate pressure on the pot just after it has been taken off the wheel. These decorations are termed roulette decoration.
Painted decorations can be so varied that any typological designation of all of them is not possible. Nonetheless we do make distinctions between pure geometric lines, crosses, circles, checker board, diamond etc. from natural depictions of wheat stock, pipal leaf, scorpion, stag, peacock or the like. Seldom are these depictions realistic.
There is always a degree of stylization involved in them. The areas covered with decoration, the normal range of depictions in these decorations and the colour used often tend to show uniformity within a given culture. This has led many authorities to uses such terms as “Harappan ware” or “Jorwe ware”, or the like.
Strictly speaking these usages are unscientific on many accounts. Firstly, all sherds found from Harappa need to be conforming to what is meant generally by Harappan ware. Secondly, such terms soon lead to crystallizing all traits of a culture with in the ambit of the predefined ceramics. That is, if we find a few X ceramics within an otherwise Y ceramics assemblage we do not hesitate to conclude a contact between X and Y cultures.
A culture by no means can be perceived merely on a predefined ceramic feature. Besides, internal heterogenicity within the culture is completely disregarded in this kind of ascriptions. Ceramic types or type like categories are attempted on the basis of the above four aspects but these types by no means can be conceived of as finite in number.
These are mere aids to conceiving an extremely varied situation through time. Shapes of the pots are often the most helpful indicators of a broad cultural area. To reconstruct this shreds with natural rims are matched against circles with known diameters and the diameter of the pot-when unbroken-is determined. A straight line equal to the reconstructed diameter is then drawn on a drawing sheet.
The shred is held at the end of this line in such a manner that the natural rim faces the line. The contour of the shred in profile is then drawn. On the other end of the coin the same contour is repeated in opposite direction and at once a tentative shape of the pot of which the sherd forms a part becomes apparent.
These shapes can at the most reveal the feature of the lip, neck and part of the body. The bottom of the pot still remains unknown. For this a separate estimation of the broken bottoms from within the collection needs to be done. Similarly spouts, if any, have to be likewise reconstructed.
Unfortunately, unlike Stone Age analysis no standard expression to describe these features is there in ceramics. We may cite below one of the best attempts on ceramic shapes as an example for a beginner to formulate his own approach.
Jim Shaffer (1978) in his analysis of Said Qala Tepe ceramics divided a vessel into 3 zones:
(i) The lip form,
(ii) The base form and
(iii) The vessel form.
The lip is defined as the area where the exterior and the interior wall surfaces cease to be parallel. This area should be located within 2 cm of the vessel orifice. A suitable classification of various forms of lips can be very important in deciding a ceramic trend.
In the same way there can be several base forms identified. Vessel forms are categorized as bowls when their diameters are greater than or equal to their heights. Further the maximum diameter in bowls always occurs at the orifice or within 2 cm of the orifice. If the height is less than half the diameter such shapes can be designated as dishes. If the vessel has a height which is more than the diameter it is called Jar.
d ≥ h Bowls
(D/2) ≥ h Dishes
d < h Jars
There may be Jars with heights more than the diameter but maximum diameter is located in the lower two-third which should be identified as simple Jars but in cases where the maximum diameter is located in the lower one-third such jars may be called Beaker/Goblet/small Jars. The profile of the vessel can often be used to add further information on the shape.
For instance, a carinated vessel refers to a bowl in which the body instead of being convex in profile has a sharp angularity. Similarly bodies can be spherical, goblet like or even cylindrical. A ceramic type, therefore, refers primarily to the shape and decoration but can include fabric and firing as well to indicate the technique.
Under Chalcolithic techniques the most significant innovation had been the knowledge of metal extraction. This not only required the identification of ore and then its preparation for the furnace with the addition of adequate slag before firing but also casting the metal into different required shapes as well. Obviously this was a group activity and demonstrates both the knowledge and organizing of labour and resource for its implementation.
The constant need for fuel for the furnaces must have kept a battery of workers constantly engaged in cutting trees, drying them and transporting them while another group must have been busy quarrying the ore, transporting them and preparing them. A culture can take off as a successful Chalcolithic phase only when an adequate demographic structure couples with an ideological and social structure suited to this group activity is reached.
It is not surprising; therefore, that terracotta figurine, spindles, bricks, bangles and many other allied cultural materials materialize during this stage of culture. We shall refer students of prehistoric technology at this stage to more specialized works to learn about the techniques of preparation of most of the other cultural materials.