Terminology
Clay: Earth substance that is plastic or moldable
Ceramics: The art of working with clay
Kiln: Large oven used to bake clay
Firing: Baking the clay to permanently harden it
Form: Three dimensional artwork
Reinforcing Coil: Coil added in the seam between two slabs to hold the slabs together
Exposed Coil: Coil design which can be seen on the exterior of a vase.
Unexposed Coil: Coil design which cannot be seen on the exterior of a vase; the surface has been blended and smoothed so the coils can no longer be seen.
Lip: The opening of a form
Foot: The bottom of a form
Body: The middle portion of a form
Symbolism: Using symbols, shapes, images, or icons to represent an idea
Stages of Clay
Slip: Watery clay, often used as glue
Plastic: Moldable, workable clay
Leatherhard: Clay that has been allowed to dry partially; clay that has stiffened, but is still somewhat moldable
Bonedry: Clay that is completely dry and ready to be fired
Ceramic "Wares"
Greenware: Any ceramic artwork that has not been fired
Bisqueware: Clay artwork that has been fired once
Glazeware: Bisqueware that has glaze applied to the surface and has been fired for the second time
Glaze: Mixture of chemicals that is applied to the surface of bisqueware and fired; chemical mixture that melts when heated and creates a glass-like finish when cooled
Underglaze: Chemical mixture that is added to greenware to add color to the surface of the clay
Types of Glaze
Gloss: Shiny glaze
Matte: Dull glaze
Opalescent: Glaze that changes colors depending on the light and angle
Crystal: Glaze that has chunks of chemicals which burst when fired, creating a multi-colored finish
Textured: Glaze that is often multi-colored which creates a tactile finish
Satin: Semi-shiny glaze
Processes
Slipping: Adding water to the clay, blending the water in until it isn't shiny; water applied to the surface of the clay in preparation for joining two pieces of clay
Scoring: Scratching the surface of the clay; hatching the clay, before slipping, used to join two leatherhard pieces of clay
Wedging: Folding and working the clay to remove air bubbles and unify the moisture level of the clay
Pinch: Handbuilding technique that begins with a large ball of clay, which is rotated and pressed between the thumb and the fingers to create a clay form
Coil: Handbuilding technique that begins with long, thin rolls of clay, which are stacked on top of each other and blended
Slab: Handbuilding technique that begins with large, flat pieces of clay, which are joined when leatherhard
Decorative Techniques
Incising: Scratching thin lines into the surface of the clay
Piercing: Cutting completely through the wall of the clay to remove shapes
Carving: Removing large areas of clay around a design, to create a raised design (reductive sculpture)
Impressing: Pressing textured surfaces into the clay
Applique: Creating separate forms and attaching them to the surface of the form (additive sculpture)
Understanding Decorative Finishes
Glaze: Glaze is a chemical mixture that melts into a glass finish when fired. This glass finish makes the clay piece waterproof. Therefore, anything that is functional (has another purpose other than being art) should be finished with glaze. It is applied to the clay after it has been fired once (or bisque fired). There are a few disadvantages however. Glaze runs or drips when it is fired, and therefore details do not turn out very well. Glaze also cannot be applied to the bottom of the piece since it melts when it is fired. Anything on the bottom will stick to the shelf of the kiln. However, there are endless colors and types of glazes that can make any vase or clay form wonderful.
Underglaze: Underglaze is also a chemical mixture, but it is very different from glaze. This mixture is applied to greenware (clay that has not been fired yet). Underglaze is not waterproof. In fact, is basically just colored clay that is added to the surface to make the clay colorful. One reason why underglaze is used is because it does not run like glaze does. Details can be added using underglaze. Once the greenware has been fired once (bisqueware), clear glaze can be applied over the underglaze and fired again to make it shiny and waterproof.
Paint: Using paint is another way of completing a clay piece. However, paint is not waterproof. Therefore, it should not be applied to clay work that is functional or has another purpose beyond being a piece of artwork. Typically, paint is applied to clay work that is sculptural, without another purpose. Paint is not fired after it is applied. In fact, paint that is fired will turn black because of the intense heat. Paint is beneficial because endless colors are available and details can be painted. Paint can also be layered, and mistakes can be fixed. A painted form can be sealed with Acrylic Gel to make it shiny. However, this does not make it waterproof.
Understanding the Firing Process
Why does clay "explode" in the kiln?
A clay form must be bonedry (completely dry) before it is fired. If it is not completely dry, the moisture in the clay will turn to a gas and expand, and try to escape too quickly, causing the form to break into tiny pieces. Typically, a clay form should dry out for two weeks, just to be safe. The thicker the clay, the longer it takes to dry out completely.
If there is an air bubble in the clay, this will also cause the clay to break into pieces. The same thing occurs. Air is a gas that expands as it is heated. Expanding gas needs a place to go. Therefore, trapped air will break open a form as a way of escaping.
The last reason for clay "exploding" in the kiln has to do with the thickness. The basic rule of thumb is making the walls no thicker than 1 inch. Anything over an inch will probably not make it through the firing. The thicker the clay is, the more likely it will have an air bubble or will not dry out completely before firing. It is recommended that you keep the walls of the form 1/4 to 1/2 of an inch thick, just to be on the safe side.
When is it necessary to score and slip? Most of the time when joining two pieces of clay, slipping both pieces and blending the seams between the two pieces is all that needs to occur. However, sometimes scoring needs to be done before the slip is added. When the moisture levels of the two pieces of clay that are going to be joined are drastically different, it is recommended to score first, then slip. Scoring is just scratching lines into the surface of the clay. Once the slip is added,
Ceramics: The art of working with clay
Kiln: Large oven used to bake clay
Firing: Baking the clay to permanently harden it
Form: Three dimensional artwork
Reinforcing Coil: Coil added in the seam between two slabs to hold the slabs together
Exposed Coil: Coil design which can be seen on the exterior of a vase.
Unexposed Coil: Coil design which cannot be seen on the exterior of a vase; the surface has been blended and smoothed so the coils can no longer be seen.
Lip: The opening of a form
Foot: The bottom of a form
Body: The middle portion of a form
Symbolism: Using symbols, shapes, images, or icons to represent an idea
Stages of Clay
Slip: Watery clay, often used as glue
Plastic: Moldable, workable clay
Leatherhard: Clay that has been allowed to dry partially; clay that has stiffened, but is still somewhat moldable
Bonedry: Clay that is completely dry and ready to be fired
Ceramic "Wares"
Greenware: Any ceramic artwork that has not been fired
Bisqueware: Clay artwork that has been fired once
Glazeware: Bisqueware that has glaze applied to the surface and has been fired for the second time
Glaze: Mixture of chemicals that is applied to the surface of bisqueware and fired; chemical mixture that melts when heated and creates a glass-like finish when cooled
Underglaze: Chemical mixture that is added to greenware to add color to the surface of the clay
Types of Glaze
Gloss: Shiny glaze
Matte: Dull glaze
Opalescent: Glaze that changes colors depending on the light and angle
Crystal: Glaze that has chunks of chemicals which burst when fired, creating a multi-colored finish
Textured: Glaze that is often multi-colored which creates a tactile finish
Satin: Semi-shiny glaze
Processes
Slipping: Adding water to the clay, blending the water in until it isn't shiny; water applied to the surface of the clay in preparation for joining two pieces of clay
Scoring: Scratching the surface of the clay; hatching the clay, before slipping, used to join two leatherhard pieces of clay
Wedging: Folding and working the clay to remove air bubbles and unify the moisture level of the clay
Pinch: Handbuilding technique that begins with a large ball of clay, which is rotated and pressed between the thumb and the fingers to create a clay form
Coil: Handbuilding technique that begins with long, thin rolls of clay, which are stacked on top of each other and blended
Slab: Handbuilding technique that begins with large, flat pieces of clay, which are joined when leatherhard
Decorative Techniques
Incising: Scratching thin lines into the surface of the clay
Piercing: Cutting completely through the wall of the clay to remove shapes
Carving: Removing large areas of clay around a design, to create a raised design (reductive sculpture)
Impressing: Pressing textured surfaces into the clay
Applique: Creating separate forms and attaching them to the surface of the form (additive sculpture)
Understanding Decorative Finishes
Glaze: Glaze is a chemical mixture that melts into a glass finish when fired. This glass finish makes the clay piece waterproof. Therefore, anything that is functional (has another purpose other than being art) should be finished with glaze. It is applied to the clay after it has been fired once (or bisque fired). There are a few disadvantages however. Glaze runs or drips when it is fired, and therefore details do not turn out very well. Glaze also cannot be applied to the bottom of the piece since it melts when it is fired. Anything on the bottom will stick to the shelf of the kiln. However, there are endless colors and types of glazes that can make any vase or clay form wonderful.
Underglaze: Underglaze is also a chemical mixture, but it is very different from glaze. This mixture is applied to greenware (clay that has not been fired yet). Underglaze is not waterproof. In fact, is basically just colored clay that is added to the surface to make the clay colorful. One reason why underglaze is used is because it does not run like glaze does. Details can be added using underglaze. Once the greenware has been fired once (bisqueware), clear glaze can be applied over the underglaze and fired again to make it shiny and waterproof.
Paint: Using paint is another way of completing a clay piece. However, paint is not waterproof. Therefore, it should not be applied to clay work that is functional or has another purpose beyond being a piece of artwork. Typically, paint is applied to clay work that is sculptural, without another purpose. Paint is not fired after it is applied. In fact, paint that is fired will turn black because of the intense heat. Paint is beneficial because endless colors are available and details can be painted. Paint can also be layered, and mistakes can be fixed. A painted form can be sealed with Acrylic Gel to make it shiny. However, this does not make it waterproof.
Understanding the Firing Process
Why does clay "explode" in the kiln?
A clay form must be bonedry (completely dry) before it is fired. If it is not completely dry, the moisture in the clay will turn to a gas and expand, and try to escape too quickly, causing the form to break into tiny pieces. Typically, a clay form should dry out for two weeks, just to be safe. The thicker the clay, the longer it takes to dry out completely.
If there is an air bubble in the clay, this will also cause the clay to break into pieces. The same thing occurs. Air is a gas that expands as it is heated. Expanding gas needs a place to go. Therefore, trapped air will break open a form as a way of escaping.
The last reason for clay "exploding" in the kiln has to do with the thickness. The basic rule of thumb is making the walls no thicker than 1 inch. Anything over an inch will probably not make it through the firing. The thicker the clay is, the more likely it will have an air bubble or will not dry out completely before firing. It is recommended that you keep the walls of the form 1/4 to 1/2 of an inch thick, just to be on the safe side.
When is it necessary to score and slip? Most of the time when joining two pieces of clay, slipping both pieces and blending the seams between the two pieces is all that needs to occur. However, sometimes scoring needs to be done before the slip is added. When the moisture levels of the two pieces of clay that are going to be joined are drastically different, it is recommended to score first, then slip. Scoring is just scratching lines into the surface of the clay. Once the slip is added,