Bell Ringer March 4 2015 What is clay

Bell Ringer March 4, 2015 What is clay?

Comprehensive Art Mrs. Brown

What is Clay? Clay is. . . a fine mixture of decomposed igneous rock materials and organic matter. • Clay is continuously being formed.

Over time, exposure to the elements cause the materials to break down into smaller and smaller pieces: Weathering Boulders Rocks Pebbles Fine grain = materials that make up clay.

Weathering Processes:

What is Ceramics? Objects made from any type of clay that is fired with the aid of heat

History of Ceramics • It is hypothesized that ceramics came about when humans 1 st learned to control fire. • Old methods and concepts are still used today.

Historical Ceramic Origins • Anthropologists use Stone Age clues to piece together a variety of possible theories of ceramic’s origin

Functional Purposes: Storage Vessel Examples • Greece 1600 B. C • Some jars as tall as 6 ft • Created using the coil method

Communication & Documentation: Cuneiform Script • Early system of writing in Mesopotamia • Stylus pressed into clay tablets • Record-keeping of laws, historical events, & harvests

Cylinder Seal Form of signature, or identification on important documents. Hunting Scene 2250 -2150 BCE, Mesopotamia

Spiritual & Religious Purposes: • Pots were widely used as funerary objects in prehistoric burial grounds • Contained food to accompany dead on journey to the afterlife • Infants and small children • Ceramic figurines and animals to protect the deceased.

Terracotta Warriors • Form of funerary art - buried with the First Emperor of Qin (He was the first emperor of China in 221 BCE. ) • Their purpose was to help him rule in the afterlife. • Architects are currently still excavating

6 Steps to Using Clay 1. 2. 3. 4. 5. 6. Early Preparation (Levigation) Forming Clay (5 major methods) Drying Clay Decorating Clay Glazing These two stages (5 & 6) can happen in reverse order as well. Firing

Step 1: Early Clay Preparation • Early potters dug their raw material out of the ground, and it often contained impurities such as pebbles or plant matter. • To remove these, potters would dry the clay in the sun, crush it into smaller lumps, and pick out the unwanted material. • Then, they rehydrate the dry clay to make it workable. • This method was fine for making a few pots, but it was difficult and time-consuming. ** The clay that Mrs. Brown gives you has already been through this early clay preparation process.

Modern Clay Preparation • Potters discovered it was much easier and faster to separate impurities by adding water to the clay and then pouring the liquid clay (slip) from one container to another. • This process is known as decanting. Decanting causes the coarser materials to settle on the bottom. • Another traditional method for removing impurities is known as Levigation.

Step 2: Forming Clay The earliest and simplest methods are still used today. Four Basic Hand Building Techniques: 1. 2. 3. 4. Pinch Method (oldest method) Coil Method Slab Method Molding Method

Hand Building : Process of forming pieces using hands without the use of a potter’s wheel; 30, 000 years old.

Pinch Method • Is when clay is pulled and pinched in order to shape an object with fingers. • It is the oldest form of ceramic hand building.

Pinch Pot

Pinch Method:

Two Pinch Pots Combined to create a hollow form:

Coil Method Created through long ropes/coils of clay that are of equal thicknesses are used to build a ceramic object

Coil

Coil

Slab Method • A method of rolling out clay flat to an equal thickness. • Slabs can be cut into shapes and used to construct ceramic objects.

Slab Method

Slab Method

Throwing: A method of forming clay in which the sculptor uses a pottery wheel. Throwing is NOT a technique of hand-building.

Potter’s Wheel : A machine that forms pottery using a wheel

Step 3: Drying Clay • Potters must know how to control the rate at which clay dries. Clay shrinks as it dries and, if it shrinks too rapidly, it can crack. • Clay that has dried to this point is in the leather-hard stage; when pressure is applied to the clay, the form will not easily distort. • See the following Stages of Clay.

6 Stages of Clay 1. Slip 2. Wet/Plastic Stages 2 – 4 are also known as 3. Leatherhard Greenware. 4. Bone-Dry ~Firing~ 5. Bisque (Bisqueware) ~Firing~ 6. Glazeware (Glazenware)

6 Stages of Clay 1. Slip: Liquid clay; “glue” required to attach two pieces of clay together.

6 Stages of Clay Con’t 2. Wet: Plastic clay; workable; easily manipulated. ** IDEAL * When Mrs. Brown gives you clay out of the bag it is in this stage.

6 Stages of Clay Con’t 3. Leather Hard: Clay is stiff but still damp; firm -maintains form and can be smoothed, carved, and added to. *not easily distorted, but can still be carved.

6 Stages of Clay Con’t: 4. Bone-dry: Water has evaporated from the clay; form is brittle and ready to be fired. ** Clay becomes lighter in color

6 Stages of Clay Con’t 5. Bisque (Bisqueware): fired once; ready to be glazed then fired a second time.

6 Stages of Clay Con’t 6. Glazeware: Objects that have been fired a second time after glaze has been applied.

R*E*C*Y*C*L*E : Clay may be recycled through the Bone Dry stage by simply rehydrating it. **Once clay has been fired it becomes permanent – it can no longer be recycled.

Step 4: Decorating Clay • Impressing uses an object to press or stamp a design into the clay. • Combing marks the surface of the clay with uniform lines. • Burnishing involves rubbing and polishing the surface with a smooth stone or piece of hard wood.

Incising – Carving or cutting into the clay surface with a tool.

Step 5: Glazing • Glaze: A coating of liquid glass that is applied to a clay surface that melts together and forms a decorative and protective surface.

Glaze also makes your ceramic piece: • Colorful • Food Safe (check glaze label. ) • Water Proof

Step 6: Firing The earliest pottery was fired in open fires.

Firing Methods The main methods of firing clay are: Open Firing: in which the vessels and fuels are set together. Kiln Firing: in which the vessels and fuels are separated.

The Kiln: • Chamber for firing your clay. • Clay MUST be Bone Dry to fire. • You must fire your clay for it to become permanent.

Kiln (Con’t) • A kiln can reach temperatures of 2, 500 degrees F and higher. • Your oven at home possibly reaches 500 degrees - at the most.

The Kiln

The Firing Cycle 8 -12 hours = to heat to maximum temperature. + 8 -12 hours = to cool 16 -24 hours for firing cycle. ** That’s why it takes longer to get your Ceramics projects back.

What are the 3 Variables of Clay? 1. Plasticity 2. Moisture 3. Heat

Plasticity: • Workability • Is the quality of clay that allows it to be easily manipulated and still maintain its shape. • Ideal texture for clay = similar to play-dough

Plasticity is. . . • The ability to hold together while being shaped (workability) Create the Coil - Does it stretch and bend without breaking? Plastic - Test It! Wrap a coil around your finger. If it cracks, the clay is not plastic. Not Plastic

Moisture • • All clay contains water. Clay dehydrates when exposed to air. Add water to clay to make it more plastic. Too little or too much water causes clay to become less plastic. Tip: Mist clay with damp sponge. ALWAYS wrap your projects with plastic (and/or a wet cloth) before storing.

Heat Fire or heat makes the shape permanent and returns the clay to its rocklike state. • Firing at temperatures ranging between 500 - 800 degrees Fahrenheit changes the physical state of clay mineral crystals into a hard, stable medium. • When clays are heated above these minimum temperatures, they become ceramics.

Other Ceramics & Clay Vocabulary To Know:

Kneading: • Process of pushing clay together.

Wedging: • Process of slamming, kneading, or pushing clay together.

How does Wedging/Kneading help? 1. 2. 3. 4. Removes air bubbles trapped in the clay. Equalizes moisture. Makes clay texture uniform. Re –forms smaller pieces into one big one. **You MUST ALWAYS wedge/knead first BEFORE using your clay.

Score: • Means the process of roughing up the edges of clay with a tool in order to join two pieces of clay together. You must always: “score, slip, and press” when joining any two pieces of clay together.

Functional = pottery that serves a purpose or does a job. Examples include: dishes, vases, bowls, cups or plates.

Aesthetics: • The visual beauty or pleasurable qualities of an object.

Sculpture in the Round: • A freestanding sculpture that is meant to be seen from all sides. Chris Gustin

Golden Rules of Ceramics: • Always WEDGE/KNEAD clay first. • Score, slip, and press ALWAYS when joining two pieces of clay. • No trapped air! – poke escape hole! • Clay must be no thicker than the tip of your thumb. • Always cover clay fully so that it will not dry out.