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Pottery Making

What is Pottery?

The term pottery is pretty vague and has several meanings. Some simple definitions:

POTTERY

pots, usually functional vessels, that are made by hand out of clay that must be fired.

So when we talk about making pottery, we will be thinking in terms of making clay vessels by hand.

Ceramic  Safety

pottery studio Just like anything else, safety first! Making pottery isn’t usually considered a highly dangerous activity but there are some things to watch out for. Some hazards to avoid:

clay dust – avoid breathing clay dust at all costs to avoid lung damage from the silica. Mop, don’t sweep; sponge, don’t brush, wear a respirator when exposed to dust of any kind. (CDC, more info)

hot kilns – kilns get extremely hot and should be treated with caution.

sharp tools, equipment – be careful not to poke, cut or smash any part of your body as you are working.

unhealthy ergonomics – bending over a wheel or work surface for hours is not good for your back.

lifting too much – heavy clay, buckets of glaze, boards full of pots, etc.

toxic chemicals – keep yourself and the users of your pots safe by understanding or avoiding toxic materials.

dry skin – okay, not exactly dangerous, but the clay does seem to suck the moisture out of hands, affecting some people more than others.

And of course, use common sense! Don’t put plastic bags over your head, don’t drink the glazes, don’t leave broken pots strewn across your work space, etc.

Tools,  Supplies, and  Equipment

Minimum: clay, often bought pre-mixed in 25 or 50lb. boxes but can also be dug or mixed yourself.

Clay

A substance made of natural materials which, combined with the right amount of water, is soft and plastic, and when heated to a high enough temperature, becomes hard and glass-like.

Common  Pottery  Tools

non-stick work surface

ribs – wood, metal, rubber, plastic of all shapes and sizes.

carving and cutting tools – including fetling knives, cut off wire, loop/ribbon tools, needle tools

stamps and texture tools – including pattern rollers, rubber stamps, handmade bisque stamps, etc.

brushes – a variety of shapes, sizes, and materials

sponges – natural sea sponges, special pottery sponges, cheap rectangle sponges, etc.

measuring devices – including scales, rulers, calipers

rolling pin

Common Pottery Supplies

clay

glaze

slip

raw materials

plastic sheets/bags

ware boards

buckets and storage

Common Pottery Equipment

pottery wheel

slab roller

extruder

kiln

pug mill

wedging table/workbench

Preparation

Minimum: good, workable clay. It should be free of air bubbles and without hard or soft lumps.

Most potters wedge or knead clay to prepare it for use. Some clay preparation techniques to consider:

§  Ram’s Head Wedging

§  Spiral Wedging

§  Stack and Slam Wedging

§  Pugging

When the clay is prepared check to make sure your workspace is ready too. This could include a non-stick surface to work on, water, clean and sharp tools, plastic to cover work, a place for work to dry, etc. What you need will depend mostly on how you make your pottery. Making small pinch pots requires minimal space, few tools, a small place to let the pots dry, a small kiln and some glaze. But throwing, trimming, glazing and firing large jugs would require a pottery wheel, many tools, a large kiln and plenty of space to work and store the jugs.

Creating  Forms

Minimum: make a simple pinch pot with your hands.

making  pottery  on  the  wheel

Making pottery on the wheel seems to be the most recognizable forming technique. A pottery wheel is a device that spins around at various speeds. Clay is attached to the wheel head and is shaped with hands or tools as it spins around. After the pot is formed it is usually cut off the wheel to dry.

Slab  Pots

Clay is rolled, cut, stretched, or pressed flat to create slabs. These slabs can be cut into shapes, joined together, or altered to form vessels or sculptural pieces.

Coil  Pots

Clay can be rolled, cut, or extruded into long rope-like coils. These coils can be attached to each other to create the walls of a pot or interesting surface designs.

Extruding  Pots  and  Parts

Clay is pushed through a die which can create coils, strips or even hollow forms. Extruded parts can be combined to create vessels or altered to create handles or other appendages.

Using  Ceramic  Molds

A mold is usually an absorbent surface in the shape of the inside or outside of the pot to be formed. Ceramic molds are a popular way to create multiple pots that are the same size and shape. There are many different mold techniques including hump and slump molds, slip casting, jigger and jolly, press molds etc.

Parts  of  a  Pot

As you learn to make pottery it helps to identify different parts of a pot, especially for communication or critique.

Details  and  Embellishments

This is an optional step that can happen after the main form is created. Basically, anything that you can do to change the original form in some way falls into this category.

Altering  the  Form  or  Surface

ü Pinching

ü Paddling

ü Cutting and Re-assembling

ü Piercing

ü Stamping/Texture

ü Crackling with Sodium Silicate

ü Adding Clay

ü Sprigs

ü Slips / Slip Trailing

ü Appendages

ü Handles

ü Spouts

ü Knobs

ü Lids

ü Covers

ü Removing Clay

ü Carving

ü Sgraffito

ü Drilling

ü Faceting;

ü Scraping

ü Chattering

ü Darting

ü Trimming or Turning

ü Bisque Firing

bisque  fired  cups

Optional. Also called biscuit firing. Many potters bisque fire pots to make them more suitable for glazing or other surface decoration. When the pots are finished and completely dry they are fired to a high enough temperature to make them hard and permanent – similar to glass but porous. The bisque firing is not hot enough to fully vitrify the clay which will usually happen in a later, hotter firing. One exception is some low-fire clays which can be bisque fired at a slightly higher temperature than when glaze fired. Many potters bisque fire to cone 04 or around 1945F.

Surface  Decoration

Optional. Some potters consider texture or carving to be surface decoration. This is technically true and makes sense. But for this article, we’re going to define “surface decoration” as anything other than clay that is added to the surface of a pot. Some techniques require the decorating to be done before the pot is bisque fired. Many techniques are applied to bisque fired pots. Potters often use multiple decorating techniques on a single pot. Some of the techniques below can also be combined with techniques to alter the clay above.

Glazing

A mixture of materials that, when fired, will melt and fuse to the clay, usually creating a glassy surface.

pottery  glaze

Many potters apply glaze to their pots to add color, texture or functionality. Glaze, after reaching the proper temperature, usually becomes a hard, glassy surface on the clay to increase the aesthetic properties and/or the functional properties. Some potters mix their own glazes but commercial glazes can be purchased already mixed, added to water and ready to apply. Glazes can be applied by brushing, dipping, pouring or spraying.

other techniques similar to glazing or are often combined with glazing:

ü Underglaze

ü Stains

ü Engobes

ü Slips

ü Resists

Atmospheric  Decoration

When pots are fired, sometimes the air surrounding them carries chemicals which land on the pots in the kiln or a saggar. These chemicals can melt to the pot and often produce interesting markings, a range of surface texture and incredible colors. Results are often more random than applying only glaze to the pot. Chemicals that can become part of a pot during firing include:

ü Ash

ü Soda

ü Salt

ü Other chemicals

ü Natural materials

ü Smoke/Carbon

ü Imagery/Image Transfers

ü Ceramic Decals

ü Screen Printing

ü Stencils

ü Hand illustration: brushwork, carving, etc.

Cold  Finishes

A cold finish is any material that can be applied to a pot, usually for decorative purposes, which doesn’t require another firing. These types of finishes are usually applied to sculptural pieces because most of these finishes are not recommended for use with food or drink. Common cold finishes include: any kind of paint, many kinds of wax, shoe polish, stains, dye, glue, sap, metal leaf, sealers… really you could try just about anything. As you choose your finish you may want to keep in mind things like ease of application, light fastness, durability, strength of the bond to clay, the environment the piece will be displayed, etc.

Firing  Pottery

pyrometric cones for firing pottery

cones for firing pottery

There are numerous ways to fire pottery. The way that a pot is fired will be one of the main factors  in the look of the finished pot. You could fire the same pot in two different kilns or even two different areas of the same kiln and get completely different results.

Pottery  Kilns

An insulated chamber which can reach and maintain temperatures high enough to change clay and glaze into a permanent object.

Kilns are often categorized or described by features such as:

Source of heat – electricity, natural gas, propane, wood, other combustibles.

Material – hard brick, soft brick, ceramic fiber.

Air flow – updraft, down-draft, cross-draft.

Shape – catenary arch, sprung arch, single-chamber, multi-chamber, oval, octagon, car, train, snake, etc.

Atmosphere – neutral, oxidation, reduction.

Common Kilns and Firing Styles

Electric Kilns – Often made out of soft bricks, usually an oxidation or neutral atmosphere, heated by coils carrying electricity.

Gas Kilns – propane or natural gas, often used to achieve a reduction atmosphere.

Wood Kilns – most are larger than electric and gas kilns, heated by wood combustion.

Pit Firing – pots are placed in a pit or barrel along with wood, sawdust and other combustibles.

Saggars – containers that hold, protect, or create unique atmospheres around individual pots while firing.

Raku – the kiln is opened mid-fire and red hot pots are removed and placed in combustible material to achieve unique characteristics.

Finishing  the  Pots

bowl with glaze defectsAfter the kiln has cooled and pots are removed sometimes a little extra work is involved. Results don’t always turn out as expected or the process can leave undesirable qualities on a pot. Sometimes a pot can be fixed or re-fired. Sometimes it is a lost cause. If you make enough pots you’ll eventually get to try some of the following:

·       Cleaning

·       Grinding bottoms

·       Sanding rough spots

·       Polishing

·       Re-Firing

Further  alterations  to  fired pots

Smashing the really bad pots

Learn More about Pottery Making

More detailed information will be added here in the future. There are also plenty of great resources available including great pottery websites. Pottery Books and Resources