ceramics process and early civilization. origins of ceramics clay has been shaped and formed as far...
TRANSCRIPT
Ceramics
Process and Early Civilization
Origins of Ceramics
Clay has been shaped and formed as far back as the Ice Age (37,000-12,000 BC). Representations of animals have been found throughout Europe.
Ceramics
Clay is transformed into ceramics when it is heated to a temperature between 1680 degrees and 2420 degrees Fahrenheit. The pottery becomes hard and retains a permanent shape.
It was not until 6000-4000 BC that knowledge of the firing process became well known. History has left no record as to how the ceramic process was actually discovered. There are three theories as to how the firing process was discovered.
Early Decoration
Around 4000 BC the first glazes were developed in Egypt. Glazes serve both a practical and decorative purpose. The Egyptians first used the glazes to decorate beads and tiles.
Source of Clay
A significant portion of the Earth’s crust is composed of granite
Clay
Clay is produced through the weathering of granite.
Granite is the parent rock of clay. When broken down it produces feldspar.
Feldspar is composed of alumina, silica and alkali.
Clay
Further weathering replaces the alkali with water. Clay, in its purest form is identified,chemically, as:AluminaSilica Water
ORAl2O3 * 2SiO2 * 2H2O
Pure Clay
Pure clay would be white, soft and mushy.
Impurities
Clay usually contains a number of materials which allows it to become more workable, as well as more attractive. These impurities may alter the:
Maturing Temperature
Color
Texture
Plasticity
Porosity
Properties of Value
Clay has three primary characteristics which make it useful for pottery:
Plasticity
Porosity
Vitrifiability
Plasticity
The ability to form or mold a piece of clay, and the fact that the clay will then hold that shape.
Porosity
Clay must contain water in order for it to function in the plastic state.
The water must be able to evaporate out of the ware completely before the piece is placed within the kiln for firing.
The porous nature of clay allows this moisture to evaporate.
Vitrifiability
The melting or fusing of portions of the clay body at specific temperatures.
This allows the fired object to be exposed to moisture, and still retain a hard, firm shape.
Stages of forming, construction and decoration
Plastic
Leather Hard
Bone Dry
Bisque Fire
Glazing
Plastic
During this stage the clay is soft, wet and pliable. It is during this stage that most ceramic pieces are formed. Types of construction during this stage are:PinchDrapeCoilSlabCore MoldsWheel ThrownSlip Casting
Leather Hard
The clay still contains considerable free water, but enough has evaporated so that the clay pieces are firm enough not to bend. The relatively high moisture content allows the joining of these somewhat rigid pieces of clay. Dry clay cannot be joined to another piece of dry clay. Type of construction during this stage:Slab
Bone Dry
All free water has evaporated. The piece is now ready for the first firing. All free water must be eliminated in order to avoid bursting within the kiln.
Green ware
These first three stages result in green ware. This term refers to any ceramic object which is complete in construction but has yet to be fired.
Bisque Fire
The green ware is put into the kiln and heated to approximately 1856 degrees Fahrenheit.
There is partial fusing of clay particles.
After this stage, green ware becomes bisque ware.
•
Glaze Fire
At this time the bisque ware is usually (not always) coated with a layer of glaze. This material is a liquid mixture of a variety of glass-forming materials. This process accomplishes two things:
Seals
Decorates
Glaze Fire
The pot, with its coating of glaze is returned to the kiln for another firing. The glaze fire is usually at a higher temperature than the bisque fire. In our case the glaze firing is usually 2350 degrees Fahrenheit. This firing melts the glaze, fuses it to the pot, and fully matures the clay body. Total shrinkage at this point is 10-15%.
Glaze Fire
•
Oxidation Glaze Fire
Oxygen rich atmosphere.
Glaze reacts to the oxygen in the air and produces a clear, brilliant color.
Clay maintains a clear color as well.
Reduction Glaze Fire
Oxygen depleted firing atmosphere.Airflow is reduced at certain temperature and the open fire is moderately smothered, causing incomplete combustion.Oxygen is drawn from materials in the glazes and clay body.Allows for multiple glaze effects from different metallic oxides.
Raku
Pieces are fired quickly to a low heat.When the glaze has matured, the piece is pulled from the kiln and placed into a receptacle containing combustible materials.Crazed (cracked) surfaces, metallic flashing and other special effects are unique to this process.
Clay Types
Earthenware
Stoneware
Porcelain
Earthenware
Matures at 1856 F
Color is usually red-brown, but can also be white
Light in weight
Fairly porous.
Usually smooth
Stoneware
Matures at 2205 F or higher
Color is usually brown, gray, buff or tan
Usually rough in texture
Quite hard, dense and heavy
Type of clay used at VHS
Porcelain
Matures at 2205 F or higher
Color is usually white
Surface is very smooth and glasslike
Extremely dense
Pyrometric Cones
They are used to accurately measure the temperature within the kiln. These cones are made from clay that is formulated to melt at a specific temperature. Cone numbers are applied to clays and glazes as a universal method of determining firing temperatures and compatibility.
Firing Temperatures
Cone 06 is the usual temperature for our bisque fire, and is the maturing temperature for earthenwares and low fire glazes.
Cone 06 is 1856 F
Cone 10 is the temperature at which our stoneware clay and glazes mature.
Cone 10 is 2350 F
Elements and Principles of Art
The elements of art are the building blocks of art. Think of them as the ingredients that artists use to create an artwork.
The Elements of Art.
ColorValue Line TextureShape Form Space
Color
Color is produced by the way our vision responds to different wavelengths of light. When a ray of white light passes through a glass prism, the ray is bent creating six individual bands of color.
Color
Colors have three properties that can be defined and measured:
Hue
Intensity
And Value
Hue
Hue – refers to the name of a color itself, such as “blue” or “red”. For easy study the colors of the spectrum are arranged in a circle called a color wheel.
Intensity
Intensity – The quality of brightness and purity of color. Adding neutral colors to a pure hue results in a loss of intensity.
How would you describe the use of color in this Picasso painting?
Compare and contrast the way that color is being used on these two pots
Value
Value- The lightness or darkness of colors.A color plus white = TintA color plus black = Shade
Value
This painting by Picasso is made up primarily of shades and tints of the color blue.
How would you describe the use of value in David Roberts naked raku vase?
Line
Line- a path of a moving point through space, refers to the continuous mark made on some surface by a moving point. It may be two-dimensional, three dimensional or implied. Often it is an outline, contour, or silhouette.
Line
Has five characteristics:Length
• Width• Curvature• Depth• Texture
How is Elaine Coleman using line on this porcelain vase?
Shape
• Formed by lines that enclose a space• Two dimensional, only have a height
and length• Can be geometric or organic • A real or imaginary object defined or
determined by the other elements
Shape
• This painting by Mondrian is mostly comprised of shapes.
How would you describe the use of shape on this piece of Pueblo pottery?
Form
• Three dimensional, has height, length and depth
• Can have one continuous surface or many surfaces.
Form
• Does this sculpture by Brancusi have a continuous surface or is it multi-surfaced?
How could you describe the forms utilized in Christa Assad’s teapot?
Texture
• Texture- refers to the surface quality or “feel” of an object, its smoothness, roughness, or softness. Textures may be real or implied.
Texture
• Is this painting by Van Gogh an example of real or implied texture?
What type of textures do you see in Jack Troy’s tea bowl?
Space• Space is an empty place or surface in or
around a work of art. Space can be two-dimensional, three-dimensional, negative and/or positive.
Positive and Negative Space
Space
• In 3D Art positive space refers to the object itself and negative space is the air that surrounds it.
How does the element of Space affect the way we view this vase by Jennifer McCurdy?
The Principles of Design
• The principles are the different ways artists can use the elements to create unified works of art.
The Principles of Art
• Balance• Emphasis• Harmony• Variety• Movement• Rhythm• Proportion
Balance-
refers to a way of combining elements to add a feeling of equilibrium or stability to a work of art. Balance can be of three kinds : symmetrical, asymmetrical and radial.
Christ Delivering the Keys of the Kingdom to Saint Peter, Sistine Chapel 1481-1483 by Perugino
How would you describe the balance of this sculpture by Megan Puls?
Emphasis
• Using elements of art to develop points of interest to pull the viewer's eye to important parts of the body of the work.
• Isolation of an element
• Placement
Do you see a focal point in this piece by Anna Whitehouse?
• Harmony- refers to a way of combining a similar elements in an artwork to accent their similarities.
• Repetition of shapes and colors can create a sense of harmony.
How did Tom Coleman and Frank Boyden use the elements of art to create harmony in this collaborative work of art?
Variety
• Refers to the differences in the work.• You can achieve variety by using
different shapes, textures, colors and values in your work.
Movement & Rhythm
• Movement-Adds excitement to your work by showing action and directing the viewers eyes throughout the picture plane.
• Rhythm-a type of movement in drawing, painting and sculpture. It is seen in repeating of shapes and colors. Alternating lights and darks also give a sense of rhythm.
Proportion
• Proportion- refers to the relationship of certain elements to the whole and to each other.
Is proportion or scale important in this work by Jim Denevan?
Peter Voulkos
Patrick Crabb
Charlie Riggs
Tom Coleman &Frank Boyden
Paul Soldner
John Mason