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The Horace Mann Ceramics Studio is located on the 4th floor of Fisher Hall.  It is a well equipped facility with 2 large working tables, a large canvas covered wedging table, and a plaster table for drying and reclaiming clay.  There are 12 electric potters wheels, a slab roller, extruder, an electric kiln (10 cubic feet) and a large gas kiln.  The glazing area includes commercial underglazes, cone 6 glazes, dry chemicals for advanced students to experiment with glaze development, and coming soon ... a selection of cone 10 reduction glazes.  There is a student accessible ceramics library containing books and magazines, and a computer lab just down the hall which students can access for research.  The studio is equipped as such to enable each student to fulfill their own artistic vision.  Traditional techniques are thoroughly explored in the classroom while experimentation is strongly encouraged.  The HM Ceramics studio has an "open door" policy.  Students are encouraged to work outside of class, and interested non-ceramics students, and faculty, are always welcome to explore what our studio has to offer. 

Course Descriptions:

Ceramics I (Beginning Ceramics) is a year long course that is an introduction to the ceramics medium.  Students explore both utilitarian and sculptural aspects of working in clay through a variety of challenging assignments,  The course focuses on the handbuilding techniques of pinching, coiling, slab construction, and an introduction to the potters wheel.  Students are also exposed to a variety of finishing techniques that may include, low fire glaze and underglaze, cone 6 glazes, oxide washes, and non-fired finishes.  Students gain some exposure to the technical aspects of clay and glaze composition, what occurs during a kiln firing, and to ceramic history.   Availability: 3 sections of 12 students/section.
CI: Syllabus

Ceramics II (Beginning Wheel Throwing) is a year long course that focuses on the potters wheel as a means to an end.  It is a rigorous course where students engage in the process of the potters wheel creating utilitarian ceramic art.  Cylinders, bowls, cups/mugs, vases, pitchers, lidded jars, and teapots are covered, as well as trimming leather hard clay on the wheel. Students also explore the various combinations of cone 6 glazes.  Students leave this course with a working knowledge of the potters wheel, form, utility, aesthetics, and begin to develop their own creative voice. Availability: 2 sections of 12 students/section.
CII: Syllabus


Ceramics III  (Advanced Ceramics)  is a year long course.  In Ceramics III, students are issued challenging assignments/ideas to work through.  The technique and manner of which they approach the challenge is the students choice.  All of the studio's materials and equipment are at the students disposal to fulfill their own artistic vision.  Technical information, demonstrations, and consultations are issued based on the students needs.  In this course, personal discovery and creative freedom are paramount.  Availability: 1 sections of 12 students.
CIII: Syllabus

Ceramics IV and Ceramics Honors are independent study courses that meet with the Ceramics III group.  In Ceramics IV/Honors, students are expected to be self motivated and eager to challenge themselves.  Specific assignments give way to the students own creative vision.  Students develop their own set of problems, research, and refer to the instructor as a resource for information and technical guidance.  Ceramics IV=5 meeting periods/cycle - Honors=10 meeting periods /cycle.
CIV/HONORS: Syllabus


Bats: flat disks made of wood, plaster, or plastic which attached to wheel head of a potters wheel so a pot can be easily removed.

Bisqueware: once fired clay, transformed into a new hard, yet porous, ceramic material, ready for glazing.

Bone Dry: dry, chalky, and brittle clay, ready for bisque fire

Clay: earthy mixtures created by eroded rock, pliable earth that hardens when fired. link

Clay Body: Clays and other minerals mixed to form a desirable clay mixture.

Coiling: creating a form by layering coils of clay. Coils of wet clay are attached by pinching and pressing.

Cones: long thin pyramid shape sticks that melt at specific temperatures, used to monitor kiln performance. link

Craft: a trade or art requiring special skill.

Craftsmanship: display of technical skill and knowledge of one’s craft; careful consideration of detail and technique when working with your clay.

Earthenware: a clay body that generally contains impurities such as organics and iron oxide. Generally vitrifies at a low temperature.

Electric kiln: Kiln that is powered by electrically heated elements, ideal for oxidation firings.

Extruder: a device used to squeeze clay through a particular shape, can create long shapes eith solid or hollow.

Firing Temperature:
Low Fire: Clay and glazes that melt (or mature) at a relatively low temperature. Typically fired from cone 06 (1845 F) to cone 04 (1940 F).

Mid-Range Fire: Typically refers to CONE 6 clay and glaze that melt at a higher temperature than low fire glazes. (cone 6 = 2245 F)

High Fire: Clay and glazes that melt at a high temperature. Typically Cone 9 (2345 F) or cone 10 (2381 F)

Foot: bottom or lowest point of a pot; acts as a pedestal for a pot creating a sense of form floating in space; sometimes in the form of a trimmed ring.

Gas Kiln: Kiln heated by a combination of gas and air; can be fired in oxidation or reduction.

Glaze: a liquid suspension of ceramic materials that is applied to bisqueware; forms a glassy surface when fired to its melting point. Three main components: Silica, Flux, and a 'Stabilizer' or 'Sticker'. link

Greenware: unfired clay, has 3 basic stages of dryness.

Grog: Fired and crushed clay added to a clay body to reduce shrinkage and add strength.

Handbuilding: methods used to assemble or create a piece primarily by hand.

Kiln: a chamber designed to bring clay and related materials to a high temperature; heat is generated from electricity, gas, or organic
materials such as wood.

Kiln Wash: a watery mix of clay, silica, and alumina used to coat kiln shelves, protects shelves from glaze runs.

Leatherhard: clay with most of the moisture gone, can no longer be formed, can be carved or have appendages attached – consistency of firm cheese.

Lip: area surrounding the opening of a vessel.

Oxidation Firing: a kiln firing that is fired with enough oxygen for metallic oxides in clay and glazes to form a chemical combination with oxygen. Can alter the color of clay and glazes; electric kilns fire in an oxidized atmosphere.

Peephole (or Spyhole): small openning through a kiln that allows for monitoring kiln performing, viewing cones

Pinching: process creating a form from a single lump of clay through pinching and pressing.

Plasticity: flexibility; clays ability to be easily formed into a shape and retain that shape.

Porcelain: A completely white clay body which can become translucent under proper firing conditions.

Reduction Firing: a kiln firing in which the metallic oxides in clay and glazes are deprived of oxygen thus forming a different chemical combination. This alters the color of clays and glazes.

Slip (#1): (joining slip) crude mixture of watery clay used to join 2 pieces clay.

Slip#2: (decorative slip) liquid clay, usually colored, used to decorate, sometimes called “underglaze”

Slip and Score: Process of thoroughly scratching a series of crosshatched lines and applying slip in order to join 2 pieces of clay. Typically used on 2 pieces of leatherhard clay.

Shrinkage: clay shrinks as it is drying and as it is fired ( . . . sometimes up to 12% in a high fire.

Soft Slab: process of creating a form from wet slabs of clay.

Throwing: making forms with the use of the potters wheel.

Vitrification: maturation; occurs when kiln temperature is high enough to fuse clay particles together creating a nonporous material.

Wax Resist: liquid wax that is applied to the surface of a pot, used to keep glaze from sticking to the pot, can be used decoratively to achieve a layered glaze effect.

Wedging: process of pounding and kneading clay to 1) remove air bubbles 2) increase density 3) equalize moisture

Clay is an abundant material created by the weathering or decomposition
of igneous rock.  The decomposed material is no longer as hard as the original
rock, but is a soft and disintegrating material that washes away from the parent
rock.  Clay that washes away sometimes settles close to the parent rock, referred
to as a primary clay.  Primary clays include china clay and bentonite. Clay that
travels away from the parent rock, picks up impurities, and settles in a new
location is called a secondary clay.  Secondary clays include stoneware clays,
ball clays, earthenware clays, and fire clays.  Clay comes in many varieties,
and each type of clay has unique qualities and colors. Ceramic artists often
blend a variety of clays together with other minerals to create a desirable and
interesting clay body.

One of the most important qualities of clay to a ceramics artist is clay's plasticity.
Plasticity, or workability, is clay's ability to be formed into any shape, and it's
ability to retain that shape without cracking or falling apart.  Different clays
have different levels of plasticity.  A clay that is not plastic is called a short clay.

Another important quality of clay is it's ability to be exposed to extreme heat.
When heated, clay becomes hard, vitreous, and forms a new permanent material.

When working with clay to create art, it is important to recognize how the clay
changes over time, and to know the qualities of each stage of dryness: wet,
leather hard, bone dry
.  Once you start working with a piece of clay it begins to
dry.  Although you can impede the drying process with water and covering
the clay with plastic, the clay is always drying. 

At any stage of dryness, clay can be reintroduced to a large amount of water
and be reclaimed, or recycled, back into wet clay.  The bone dry stage is the
ideal stage to recycle clay.  After clay is fired, it can not be recycled back into
workable clay
.
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Stages of Dryness: Below, is an outline of the each stage of dryness, of course there are gray areas between each stage. 

1.  Wet/Plastic Clay

  • workable clay
  • can be manipulated into any form with ease

2.  Leather Hard Clay:

  • partially dry, still contains moisture
  • cool to touch
  • consistency of “firm cheese”
  • can no longer be formed and the form cannot be altered with ease
  • clay is relatively strong
  • surface may be worked upon
  • appendages, such as handles or spouts, may be added by slipping and scoring

3.  Bone Dry Clay:

  • completely air dried
  • very brittle, can be easily crushed
  • still contains some moisture from the air
  • chalky surface
  • is no longer workable
  • appendages can not be attached
  • surface may still be worked upon, but is more limiting than when leather hard
  • ready to be bisque fired 

Glaze is a liquid suspension of ceramic materials that is applied to bisqueware.  Glaze forms a glassy surface when fired to its melting point.  A glaze has three basic ingredients:
_____________________________________________________________________________________________

Silica: (the glassmaker) Pottery glazes (and bottles, windows, etc) are made from silica.  There are many minerals that contain amounts of silica.  Silica is available to ceramic artists in a
pure powdered form called Flint.  Silica, or Flint, melts into glass at 1700C (3092F), which is too
hot for clay.  So in order to melt silica on clay, another ingredient must be added to lower the
melting point.

Flux: (melter) A flux is an ingredient that lowers the melting point of silica.  This allows a ceramic
artist create glass on clay at almost any desirable temperature.  There are many minerals that
can be used as a flux. Some of the most common ones are: calcium, magnesium, barium, potassium, sodium, lithium, and zinc (to name a few).  Some of these are available in a pure
form, while others are combined with other materials.  When a flux reacts with silica during
a kiln firing, it can be a rather volatile reaction.  A third ingredient is added to help the reaction take place.

Alumina: (the sticker) Alumina helps the melted glaze stick to the clay.  It binds the glaze to the clay surface and gives the glaze some viscosity.  Basically, it helps the glaze from sliding off the pot. 

It is the proportions of these three basic ingredients that determines the quality of a glaze.  A glaze can be matt, semi-matt, smooth, semi-gloss, or glossy.
____________________________________________________________________________________________

Oxides: (colorants) Small amounts of metallic oxides are often added to glazes to produce a variety of colors.  Colorants are added in various amounts, but typically between 1/4% and 6%. It is a chemical reaction during a kiln firing that creates the color of a glaze.  Glazes are often one color in its raw state and a completely different color and it is fired into a glass.  For example, a glaze that is pink in its raw state, may be bright blue in the fired state.  Below is a short list of some oxides and there possible fired colors.  Firing glazes in oxidation or reduction will also effect the color of a glaze. 

oxide
possibilities in oxidation
possibilities in reduction
Cobalt light-dark blue light-dark blue
Red or Black Iron yellow,red,brown,black green,blue,yellow,brown,black
Rutile tan,brown tan,brown
Copper greens greens, reds,purples
Manganese pink,brown,purple,black browns,greens,black
Nickel slate-blue,brown,green browns

 

A kiln is a chamber designed to bring clay and related materials to a high temperature.  HM's Ceramics Studio is equipped with two kilns, one electric and one powered by gas.  The electric kiln (below) has an interior that is lined with coiled elements. These elements become heated, glow, and radiate heat throughout the kiln.  The kiln walls, floor, and lid are constructed of insulation brick that reflects and contains the heat.  This kiln is equipped with a computer that can control kiln performance, but pyrometric cones are also used.  Electric kilns fire in oxidation.  Bisque firings, low temperature glaze firings, and cone 6 oxidation firings are all performed with this kiln.

Oxidation Firing:  a firing where there is plenty of oxygen available in the kilns environment for metallic oxides to go into a particular chemical combination.  Electric kilns naturally fire in oxidation and can not go into reduction.

Reduction Firing:  In a reduction firing the kilns atmosphere is deprived or oxygen.  This is generally caused by closing the damper or at the burner itself.  A reduced atmosphere causes metallic oxides to lose oxygen molecules creating a new chemical combination.  This can cause drastic changes in clay and glaze color.  For example copper in a glaze can change from green to red in a reduced atmosphere.

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Other Types of Kilns and Firing Techniques to check out:

  • Woodfire [external links] 1 - 2 - 3
  • Salt/Soda Firing [external links] 1 - 2
  • Pit Firing [external links] 1 - 2
  • Saggar Firing [external links] 1
  • Raku [external links] 1 - 2 - Mobile Raku @HM

Pyrometric cones are long and thin pyramids made from controlled compositions and have been used since the 1800's to monitor kiln performance.  Cones are temperature indicators that melt and bend at very specific temperatures. Other factors such as time and atmosphere also affect the behavior of a cone.  Each cone is numbered indicating it's melting temperature. A carefully selected series of cones is placed in a kiln so that they are visible through a small "peep" hole on the side of the kiln. During a kiln firing, the exact temperature of the kiln can be determined by viewing cones as they melt and bend.  Cones do not measure temperature as much as they measure "work heat," or the combination of time and temperature.

More Info:
Orton Pyrometric Cone Chart (pdf)

Orton Ceramic Foundation




Before and after of a Cone pack for a Cone 6 Firing (cones 5,6,7 are used).

 

 


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Instructor: Keith Renner [website]
keith_renner@horacemann.org [email]
The Horace Mann School [website]
231 West 246th St. Bronx, New York10471