Pottery

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Today's episode is from a Wikipedia article titled Pottery.

Pottery is the process and the products of forming vessels and other objects with clay and other ceramic materials,

Which are fired at high temperatures to give them a hard and durable form.

Major types include earthenware,

Stoneware,

And porcelain.

The place where such wares are made by potter is also called a pottery,

Plural potteries.

The definition of pottery used by the ASTM International is all fired ceramic wares that contain clay when formed,

Except technical,

Structural,

And refractory products.

In art history and archaeology,

Especially of ancient and prehistoric periods,

Pottery often means vessels only,

And sculpted figurines of the same material are called terracottas.

Clay as a part of the materials used is required by some definitions of pottery,

But this is dubious.

Pottery is one of the oldest human inventions originating before the Neolithic period,

With ceramic objects like the Gravedian culture,

Venus of Dolny Vestanichik figurine,

Discovered in the Czech Republic dating back to 29,

000 to 25,

000 BC,

And pottery vessels that were discovered in Jiangxi China,

Which date back to 18,

000 BC.

Neolithic and pre-Neolithic pottery artifacts have been found in Jomon,

Japan,

The Russian Varese,

Sub-Saharan Africa,

South America,

And the Middle East.

Pottery is made by forming a ceramic,

Often clay,

Body into objects of a desired shape and heating them to high temperatures in a bonfire pit or kiln,

And induces reactions that lead to permanent changes including increasing the strength and rigidity of the object.

Much pottery is purely utilitarian,

But much can also be regarded as ceramic art.

A clay body can be decorated before or after firing.

Clay-based pottery can be divided into three main groups,

Earthenware,

Stoneware,

And porcelain.

These require increasingly more specific clay material and increasingly higher firing temperatures.

All three are made in glazed and unglazed varieties for different purposes.

All may also be decorated by various techniques.

In many examples,

The group a piece belongs to is immediately visually apparent,

But this is not always the case.

The fritware of the Islamic world does not use clay,

So technically falls outside these groups.

Historic pottery of all these types is often grouped as either fine wares,

Relatively expensive and well-made,

And following the aesthetic taste of the culture concerned,

Or alternatively coarse,

Popular,

Folk,

Or village wares,

Mostly undecorated or simply so,

And often less well-made.

Cooking in clay pots became less popular once metal pots became available.

Clay remained popular for those dishes that depended on the unique qualities of clay cooking.

Main Types Earthenware The earliest forms of pottery were made from clays that were fired at low temperatures initially in pitfires or in open bonfires.

They were hand-formed and undecorated.

Earthenware can be fired as low as 600 degrees Celsius and is normally fired below 1200 degrees Celsius.

Because unglazed biscuit earthenware is porous,

It has limited utility for the storage of liquids or as tableware.

However,

Earthenware has had a continuous history from the Neolithic period to today.

It can be made from a wide variety of clays,

Some of which fire to a buff,

Brown,

Or black color,

With iron in the constituent minerals resulting in a reddish-brown.

Reddish-colored varieties are called terracotta,

Especially when unglazed or used for sculpture.

The development of ceramic glaze made impermeable pottery possible,

Improving the popularity and practicality of pottery vessels.

The addition of decoration has evolved throughout its history.

Stoneware Stoneware is pottery that has been fired in a kiln at a relatively high temperature from about 1100 degrees Celsius to 1200 degrees Celsius and is stronger and non-porous to liquids.

The Chinese who developed stoneware very early on classified this together with porcelain as high-fired wares.

In contrast,

Stoneware could only be produced in Europe from the late Middle Ages,

As European kilns were less efficient and the right type of clay less common.

It remained a specialty of Germany until the Renaissance.

Stoneware is very tough and practical,

And much of it has always been utilitarian,

For the kitchen or storage rather than for the table.

But fine stoneware has been important in China,

Japan,

And the West,

And continues to be made.

Many utilitarian types have also come to be appreciated as art.

Porcelain Porcelain is made by heating materials generally including kaolin and a kiln to temperatures between 1200 and 1400 degrees Celsius.

This is higher than used for the other types,

And achieving these temperatures was a long struggle as well as realizing what materials were needed.

The toughness,

Strength,

And translucence of porcelain relative to other types of pottery arises mainly from vitrification and the formation of the mineral molyte within the body of these high temperatures.

Although porcelain was first made in China,

The Chinese traditionally do not recognize it as a distinct category,

Grouping it with stoneware as high-fired ware opposed to low-fired earthenware.

This confuses the issue of when it was first made.

A degree of translucency and whiteness was achieved by the Tang dynasty,

And considerable quantities were being exported.

The modern level of whiteness was not reached until much later in the 14th century.

Porcelain was also made in Korea and in Japan from the end of the 16th century after suitable kaolin was located in those countries.

It was not made effectively outside East Asia until the 18th century.

Archaeology The study of pottery can help to provide an insight into past cultures.

Fabric analysis used to analyze the fabric of pottery is an important part of archaeology for understanding the archaeological culture of the excavated site by studying the fabric of artifacts such as their usage,

Source material composition,

Decorative pattern,

Color of patterns,

Etc.

This helps to understand characteristics,

Sophistication,

Habits,

Technology,

Tools,

Trade,

Etc.

Of the people who made and used the pottery.

Carbon dating reveals the age.

Sites with similar pottery characteristics have the same culture.

The sites which have distinct cultural characteristics but with some overlap are indicative of cultural exchange such as trade or living in vicinity or continuity of habitation,

Etc.

Those are black and red ware,

South-east iswell culture,

And painted grey ware culture.

The six fabrics of Cali-Bengen is a good example of use of fabric analysis and identifying a differentiated culture which was earlier thought to be typical Indus Valley civilization,

IVC culture.

Pottery is durable and fragments at least often survive long after artifacts made from less durable materials have decayed past recognition.

Combined with other evidence,

The study of pottery artifacts is helpful in the development of theories on the organization,

Economic condition,

And the cultural development of the societies that produced or acquired pottery.

The study of pottery may also allow inferences to be drawn about a culture's daily life,

Tradition,

Social relationships,

Attitudes towards neighbors,

Attitudes towards their own world,

And even the way the culture understood the universe.

Chronologies based on pottery are often essential for dating non-literate cultures and are often of help in the dating of historic cultures as well.

Trace element analysis,

Mostly by neutron activation,

Allows the sources of clay to be accurately identified and the thermal luminescence test can be used to provide an estimate of the date of last firing.

Examining fired pottery shards from prehistory,

Scientists learned that during high temperature firing,

Iron materials in clay record the exact state of the Earth's magnetic field at that exact moment.

Source Material Fabric Analysis The clay body is also called the paste or the fabric,

Which consists of two things,

The clay matrix,

Composed of grains of less than 0.

02 mm grains,

Which can be seen using the high powered microscopes or a scanning electron microscope,

SEM,

And the clay inclusions,

Which are larger grains of clay and could be seen with the naked eye or a low power binocular microscope.

For geologists,

Fabric analysis means spatial arrangement of minerals in a rock.

For archaeologists,

The fabric analysis of pottery entails the study of clay matrix and inclusions in the clay body,

As well as the firing temperature and conditions.

Analysis is done to examine the following three in detail.

How pottery was made,

E.

G.

Material,

Design,

Such as shape and style,

Etc.

Its decorations,

Such as patterns,

Colors of patterns,

Slipped,

Glazing,

Or unslipped decoration.

Evidence of type of use.

The six fabrics of Calabangun is a good example of fabric analysis.

Clay Bodies and Mineral Contents Pottery or Clay Body is a term for the main pottery form of a piece,

Underneath any glaze or decoration.

The main ingredient of the body is clay.

There are several materials that are referred to as clay.

The properties which make them different include plasticity,

The malleability of the body,

The extent to which they will absorb water after firing,

And shrinkage,

The extent of reduction in size of a body as water is removed.

Different clay bodies also differ in the way in which they respond when fired in the kiln.

A clay body can be decorated before or after firing.

Prior to some shaping processes,

Clay must be prepared.

Each of these different clays is composed of different types and amounts of minerals that determine the characteristics of resulting pottery.

There can be regional variations in the properties of raw materials used for the production of pottery,

And these can lead to wares that are unique in character to a locality.

It is common for clays and other materials to be mixed to produce clay bodies suited to specific purposes.

A common component of clay bodies is the mineral kaolinite.

Other minerals in the clay such as feldspar act as fluxes which lower the vitrification temperature of bodies.

Following is a list of different types of clay used for pottery.

Kaolin is sometimes referred to as China clay because it was first used in China,

Used for porcelain.

Ball clay,

An extremely plastic,

Fine-grained sedimentary clay which may contain some organic matter.

Small amounts can be added to porcelain bodies to increase plasticity.

Fire clay,

A clay having a slightly lower percentage of fluxes than kaolin,

But usually quite plastic.

It is a highly heat-resistant form of clay which can be combined with other clays to increase the firing temperature and may be used as an ingredient to make stoneware-type bodies.

Stoneware clay,

Suitable for creating stoneware.

As many of the characteristics between fire clay and ball clay,

Having finer grain like ball clay but as more heat-resistant like fire clays.

Common red clay and shale clay have vegetable and ferric oxide impurities which make them useful for bricks but are generally unsatisfactory for pottery except under special conditions of a particular deposit.

Bentonite,

An extremely plastic clay which can be added in small quantities to short clay to increase the plasticity.

Production of pottery Production of pottery includes the following three stages.

Making clay body,

I.

E.

Paste or putty,

Shaping and molding,

Firing and baking,

Decorating such as glazing,

Slipping,

Painting,

Etc.

Shaping Methods Pottery can be shaped by a range of methods that include hand-building.

This is the earliest forming method,

Whereas can be constructed by hand from coils of clay,

Combining flat slabs of clay or pinching solid balls of clay or some combination of these.

Parts of hand-built vessels are often joined together with the aid of slip,

An aqueous suspension of clay body and water.

A clay body can be decorated before or after firing.

Prior to some shaping processes,

Clay must be prepared such as table wares,

Although some studio potters find hand-building more conducive to create one-of-a-kind works of art.

The Potter's Wheel In a process called throwing,

Coming from the Old English word thrown,

Which means to twist or turn,

A ball of clay is placed in the center of a turntable called the wheel head,

Which the potter rotates with a stick,

With foot power,

Or with a variable speed electric motor.

During the process of throwing,

The wheel rotates while the solid ball of soft clay is pressed,

Squeezed and pulled gently upwards and outwards into a hollow shape.

The first step of pressing the rough ball of clay downward and inward into perfect rotational symmetry is called centering the clay,

A most important skill to master before the next steps,

Opening,

Making a centered hollow into the solid ball of clay,

Flooring,

Making the flat or rounded bottom inside the pot,

Throwing or pulling,

Drawing up and shaping the walls to an even thickness,

And trimming and turning,

Removing excess clay to refine the shape or to create a foot.

Professional skill and experience are required to throw pots of an acceptable standard,

And while the ware may have high artistic merit,

The reproducibility of the method is poor.

Because of its inherent limitations,

Throwing can only be used to create wares with radial symmetry on a vertical axis.

These can then be altered by impressing,

Bulging,

Carving,

Fluting and incising.

In addition to the potter's hands,

These techniques can use tools including paddles,

Anvils and ribs,

And those specifically for cutting or piercing such as knives,

Fluting tools,

Needle tools and wires.

Thrown pieces can be further modified by the attachment of handles,

Lids,

Feet and spouts.

Granulate pressing As the name suggests,

This is the operating of shaping pottery by pressing a clay in a semi-dry granulated condition in a mold.

The clay is pressed into the mold by a porous dye through which water is pumped at high pressure.

The granulated clay is prepared by spray drying to produce a fine and free flowing material,

Having a moisture content of between about 5 and 6 percent.

Granulate pressing,

Also known as dust pressing,

Is widely used in the manufacture of ceramic tiles and increasingly of plates.

Injection molding This is a shape forming process adapted for the tableware industry for the method long established for the forming of thermoplastic and some metal components.

It has been called porcelain injection molding or PIM.

Suited to the mass production of complex shaped articles,

One significant advantage of the technique is that it allows the production of a cup,

Including the handle in a single process,

And thereby eliminates the handle fixing operation and produces a stronger bond between cup and handle.

The feed to the mold dye is a mix of approximately 50 to 60 percent unfired body in powder form,

Together with 40 to 50 percent organic additives composed of binders,

Lubricants and plasticizers.

The technique is not as widely used as other shaping methods.

Jiggering and Jollying These operations are carried out on the potter's wheel and allow the time taken to bring wares to a standardized form to be reduced.

Jiggering is the operation of bringing a shaped tool into contact with the plastic clay of a piece under construction,

The piece itself being set on a rotating plaster mold on the wheel.

The jigger tool shapes one face while the mold shapes the other.

Jiggering is used only in the production of flat wares such as plates,

But a similar operation,

Jollying,

Is used in the production of hollow wares such as cups.

Jiggering and Jollying have been used in the production of pottery since at least the 18th century.

In large-scale factory production,

Jiggering and Jollying are usually automated which allows the operations to be carried out by semi-skilled labor.

Roller Head Machine This machine is for shaping wares on a rotating mold as in jiggering and Jollying,

But with a rotary shaping tool replacing the fixed profile.

The rotary shaping tool is a shallow cone having the same diameter as the ware being formed and shaped to the desired form of the back of the article being made.

Wares may in this way be shaped using relatively unskilled labor in one operation at a rate of about 12 pieces per minute,

Though this varies with the size of the articles being produced.

Developed in the UK just after World War II by the company's service engineers,

Roller heads were quickly adopted by manufacturers around the world.

They remain the dominant method for producing flatware.

Plaster Casting Specially developed polymeric materials allow a mold to be subject to application external pressures of up to 4.

0 MPa,

So much higher than slip casting in plaster molds,

Where the capillary forces correspond to a pressure of around 0.

1 to 0.

2 MPa.

The higher pressure leads to much faster casting rates and hence faster production cycles.

Furthermore,

The application of high pressure air through the polymeric molds upon demolding the cast means a new casting cycle can be started immediately in the same mold,

Unlike plaster molds,

Which require lengthy drying times.

The polymeric materials have much greater durability than plaster,

And therefore it is possible to achieve shaped products with better dimensional tolerances and much longer mold life.

Pressure casting was developed in the 1970s for the production of sanitary ware,

Although more recently it has been applied to tableware.

Tram pressing This is used to shape ware by pressing a bat of prepared clay body into a required shape between two porous molding plates.

After pressing,

Compressed air is blown through the porous mold plates to release the shaped wares.

Slip casting This is suited to the making of shapes that cannot be formed by other methods.

A liquid slip made by mixing clay body with water is poured into a highly absorbent plaster mold.

Water from the slip is absorbed into the mold,

Leaving a layer of clay body covering its internal surfaces and taking its internal shape.

Excess slip is poured out of the mold,

Which is then split open and the molded object removed.

Slip casting is widely used in the production of sanitary ware,

And is also used for making other complex shaped ware such as teapots and figurines.

3D printing This is the latest advance in forming ceramic objects.

There are two methods.

One involves the layered deposition of soft clay,

Similar to fused deposition modeling FDM,

And the other uses powder binding techniques where dry clay powder is fused together layer upon layer with a liquid.

Firing Firing produces irreversible changes in the body.

It is only after firing that the article or material is pottery.

In lower fired pottery,

The changes include sintering,

The fusing together of coarser particles in the body at their points of contact with each other.

In the case of porcelain where different materials and higher firing temperatures are used,

The physical,

Chemical,

And mineralogical properties of the constituents in the body are greatly altered.

In all cases,

The reason for firing is to permanently harden the wares,

And the firing regime must be appropriate to the materials used to make them.

As a rough guide,

Modern earthen wares are normally fired at temperatures in the range of about 1000 degrees Celsius to 1200 degrees Celsius.

Stone wares set between about 1100 degrees Celsius to 1300 degrees Celsius,

And porcelains about 1200 to 1400 degrees Celsius.

Historically,

Reaching high temperatures was a long-lasting challenge,

And earthen ware can be fired effectively as low as 600 degrees Celsius,

Achievable in primitive pit firing.

Firing Methods Firing pottery can be done using a variety of methods,

With a kiln being the usual firing method.

Both the maximum temperature and the duration of firing influences the final characteristics of the ceramic.

Thus,

The maximum temperature within a kiln is often held constant for a period of time to soak the wares to produce the maturity required in the body of the wares.

The atmosphere within a kiln during firing can affect the appearance of the finished wares,

And oxidizing atmosphere produced by allowing an excess of air in the kiln can cause the oxidation of clays and glazes.

A reducing atmosphere produced by limiting the flow of air into the kiln,

Or burning coal rather than wood,

Can strip oxygen from the surface of clays and glazes.

This can affect the appearance of the wares being fired,

And,

For example,

Some glazes containing iron-rich minerals fire brown in an oxidizing atmosphere,

But green in a reducing atmosphere.

The atmosphere within a kiln can be adjusted to produce complex effects and glaze.

Kilns may be heated by burning wood,

Coal,

And gas,

Or by electricity.

When used as fuels,

Coal and wood can introduce smoke,

Soot,

And ash into the kiln,

Which can affect the appearance of unprotected wares.

For this reason,

Wares fired in wood or coal-fired kilns are often placed in the kiln in saggers,

Ceramic boxes,

To protect them.

Modern kilns powered by gas or electricity are cleaner and more easily controlled than older wood or coal-fired kilns,

And often allow shorter firing times to be used.

In a Western adaptation of traditional Japanese raku ware firing,

Wares are removed from the kiln while hot and smothered in ashes,

Paper,

Or wood chips,

Which produces a distinctive carbonized appearance.

This technique is also used in Malaysia in creating traditional labu sayung.

In Mali,

A firing mound is used rather than a brick or stone kiln.

Unfired pots are first brought to the place where a mound will be built customarily by the women and girls of the village.

The mound's foundation is made by placing sticks on the ground,

Then pots are positioned on and amid the branches,

And then grass is piled high to complete the mound.

Although the mound contains the pots of many women who are related through their husbands' extended families,

Each woman is responsible for her own or her immediate family's pots within the mound.

When a mound is completed and the ground around has been swept clean of residual combustible material,

A senior potter lights the fire.

A handful of grass is lit,

And the woman runs around the circumference of the mound touching the burning torch to the dried grass.

Some mounds are still being constructed as others are already burning.

Firing Stages Before being shaved,

Clay must be prepared.

Kneading helps to ensure an even moisture content throughout the body.

Air trapped within the clay body needs to be removed.

This is called de-airing and can be accomplished either by a machine called a vacuum pug or manually by wedging.

Wedging can also help produce an even moisture content.

Once a clay body has been kneaded and de-aired or wedged,

It is shaped by a variety of techniques.

After it has been shaped,

It is dried and then fired.

Greenware refers to unfired objects.

At sufficient moisture content,

Bodies at this stage are in their moisture plastic form,

And they are soft and malleable,

And hence can be easily deformed by handling.

Leather hard refers to a clay body that has been dried partially.

At this stage,

The clay object has approximately 15% moisture content.

Clay bodies at this stage are very firm and only slightly pliable.

Trimming and handle attachment often occurs at the leather hard stage.

Bone dry refers to clay bodies when they reach a moisture content at or near 0%.

At that moisture content,

The item is ready to be fired.

Additionally,

The piece is extremely fragile at this stage and must be handled with extreme care.

Biscuit or bisque refers to the clay after the object is shaped to the desired form and fired in the kiln for the first time,

Known as bisque-fired or bisquit-fired.

This firing changes the clay body in several ways.

Mineral components of the clay body will undergo chemical and physical changes that will change the material.

Glaze-fired is the final stage of some pottery making or glossed-fired.

A glaze may be applied to the bisque form and the object can be decorated in several ways.

After this,

The object is glaze-fired,

Which causes the glazed material to melt,

Then adhere to the object.

Depending on the temperature schedule,

The glaze firing may also further mature the body as chemical and physical changes continue.

Decoration Methods Pottery may be decorated in many different ways.

Some decoration can be done before or after the firing.

Decoration Methods Painting has been used since early prehistoric times,

China painting,

And can be very elaborate.

The painting is often applied to pottery that has been fired once,

And may then be overlaid with a glaze afterwards.

Many pigments change color when fired,

And the painter must allow for this.

Glaze-perhaps the most common form of decoration that also serves as protection to the pottery by being tougher and keeping liquid from penetrating the pottery.

Glaze may be clear,

Especially over-painting,

Or colored and opaque.

Carving Pottery vessels may be decorated by shallow carving of the clay body,

Typically with a knife or similar instrument used on the wheel.

This is common in Chinese porcelain of the classic periods.

Burnishing The surface of pottery wares may be burnished prior to firing by rubbing with a suitable instrument of wood,

Steel,

Or stone to produce a polished finish that survives firing.

It is possible to produce very highly polished wares when the fine clays are used,

Or when the polishing is carried out on wares that have been partially dried and contain little water,

Though wares in this condition are extremely fragile,

And the risk of breakage is high.

Terra segolata is an ancient form of decorating ceramics that was first developed in ancient Greece.

Additives can be worked into the clay body prior to forming to produce desired effects in the fired wares.

Coarse additives such as sand and grog,

Fired clay which has been finely ground,

Are sometimes used to give the final product a required texture.

Contrasting colored clays and grogs are sometimes used to produce patterns in the finished wares.

Colorants,

Usually metal oxides and carbonates,

Are added singly or in combination to achieve a desired color.

Combustible particles can be mixed with the body or pressed into the surface to produce texture.

Lithography,

Also called litho,

Although the alternative names of transfer print or decal are also common.

These are used to apply designs to articles.

The litho comprises three layers,

The color or image layer which comprises the decorative design,

The cover coat,

The clear protective layer which may incorporate a low melting glass,

And the backing paper on which the design is printed by screen printing or lithography.

There are various methods of transferring the design while removing the backing paper,

Some of which are suited to machine application.

Banding is the application by hand or by machine of a band of color to the edge of a plate or cup.

Also known as lining,

This operation is often carried out on a potter's wheel.

Agate ware is named after its resemblance to the quartz mineral agate,

Which has bands or layers of color that are blended together.

Agate wares are made by blending clays of different colors together,

But not mixing them to the extent that they lose their individual identities.

The wares have a distinctive veined or mottled appearance.

The term agate ware is used to describe such wares in the United Kingdom.

In Japan the term naryage is used and in China,

Where such things have been made since at least the Tang Dynasty,

They are called marbled wares.

Great care is required in the selection of clays to be used for making agate wares,

As the clays used must have matching thermal movement characteristics.

Engob This is a clay slip that is used to coat the surface of pottery,

Usually before firing.

Its purpose is often decorative,

Though it can also be used to mask undesirable features in the clay to which it is applied.

Engob slip may be applied by painting or by dipping to provide a uniform smooth coating.

Engob has been used by potters from prehistoric times until the present day,

And is sometimes combined with sgraffito decoration,

Where a layer of engob is scratched through to reveal the color of the underlying clay.

With care it is possible to apply a second coat of engob of a different color to the first and to incise decoration through the second coat to expose the color of the underlying coat.

Engob used in this way often contain substantial amounts of silica,

Sometimes approaching the composition of a glaze.

Gold Decoration with gold is used on some high quality ware.

Different methods exist for its application,

Including 1.

Best gold,

A suspension of gold powder in essential oils mixed with a flux and a mercury salt extended.

This can be applied by a painting technique.

From the kiln the decoration is dull and requires burnishing to reveal the full color.

2.

Acid gold,

A form of gold decoration developed in the early 1860s at the English factory of Minton's Limited,

Stoke-on-Trent.

The glazed surface is etched with diluted hydrofluoric acid prior to application of the gold.

The process demands great skill and is used for the decoration only of ware at the highest class.

3.

Bright gold,

Consists of a solution of gold sulfurescent together with other metal resonance and a flux.

The name derives from the appearance of the decoration immediately after removal from the kiln as it requires no burnishing.

4.

Muscle gold,

An old method of gold decoration.

It was made by rubbing together gold leaf,

Sugar and salt,

Followed by washing to remove solubles.

5.

Glazing,

Glaze is a glassy coating on pottery,

The primary purposes of which are decoration and protection.

One important use of glaze is to render porous pottery vessels impermeable to water and other liquids.

Glaze may be applied by dusting the unfired composition over the ware or by spraying,

Dipping,

Trailing or brushing on a thin slurry composed of the unfired glaze and water.

The color of a glaze after it has been fired may be significantly different from before firing.

To prevent glazed wares sticking to kiln furniture during firing,

Either a small part of the object being fired,

For example the foot,

Is left unglazed or alternatively special refractory spurs are used as supports.

These are removed and discarded after the firing.

Some specialized glazing techniques include salt glazing,

Where common salt is introduced to the kiln during the firing process.

The high temperatures cause the salt to volatize,

Depositing it on the surface of the ware to react with the body to form a sodium aluminosilicate glaze.

In the 17th and 18th centuries,

Salt glazing was used in the manufacture of domestic pottery.

Now except for use by some studio potters,

The process is obsolete.

The last large-scale application before its demise in the face of environmental clean air restrictions was in the production of salt-glazed sewer pipes.

Ash glazing,

Ash from the combustion of plant matter,

Has been used as the flux component of glazes.

The source of the ash was generally the combustion waste from the fueling of kilns,

Although the potential of ash derived from arable crop wastes has been investigated.

Ash glazes are of historical interest in the Far East,

Although there are reports of small-scale use in other locations,

Such as the Catawba Valley pottery in the United States.

They are now limited in small numbers of studio potters who value the unpredictability arising from the variable nature of the raw material.

Underglaze decoration in the manner of many blue and white wares.

Underglaze may be applied by brush strokes,

Airbrush,

Or by pouring the underglaze into the mold,

Covering the inside,

Creating a swirling effect,

Then the mold is filled with the slip.

In glaze decoration,

On glaze decoration,

Enamel.