ARMADILLO CLAY AND SUPPLIES
  • HOME
  • Clay
    • Low-Fire (04-06)
    • Mid-Fire (5-6)
    • High-Fire (9-12)
    • Non-Fired Clay
    • Casting Slip
  • Glazes
    • Underglazes
    • Low-Fire (04-06)
    • Mid-Fire (5-6)
    • Lusters (017-020)
  • Dry Materials
    • Chemicals
    • Plaster
    • Mason Stains
  • Tools
  • Supplies
  • Equipment
    • Pottery Wheels
    • Ceramic Kilns
    • Kiln Parts
    • Kiln Furniture
    • Slabrollers
    • Extruders
    • Carts and Cabinets
    • Pugmills
  • Molds
  • Bisqueware
  • Books
  • Glass
    • Sheet Glass
    • Glass Frit
    • Glass Accents
    • Tools and Supplies
    • GLASS KILNS
  • SALE RACK
  • Services
    • Firing Services
    • Kiln and Wheel Repair
    • Custom Clay
    • Other Services
  • Gift Cards
  • Learning Center
  • More
    • About Us
    • Classifieds
    • COVID-19 INFO
    • Artist Links
    • Order Info
  • REQUEST A QUOTE
  • HOME
  • Clay
    • Low-Fire (04-06)
    • Mid-Fire (5-6)
    • High-Fire (9-12)
    • Non-Fired Clay
    • Casting Slip
  • Glazes
    • Underglazes
    • Low-Fire (04-06)
    • Mid-Fire (5-6)
    • Lusters (017-020)
  • Dry Materials
    • Chemicals
    • Plaster
    • Mason Stains
  • Tools
  • Supplies
  • Equipment
    • Pottery Wheels
    • Ceramic Kilns
    • Kiln Parts
    • Kiln Furniture
    • Slabrollers
    • Extruders
    • Carts and Cabinets
    • Pugmills
  • Molds
  • Bisqueware
  • Books
  • Glass
    • Sheet Glass
    • Glass Frit
    • Glass Accents
    • Tools and Supplies
    • GLASS KILNS
  • SALE RACK
  • Services
    • Firing Services
    • Kiln and Wheel Repair
    • Custom Clay
    • Other Services
  • Gift Cards
  • Learning Center
  • More
    • About Us
    • Classifieds
    • COVID-19 INFO
    • Artist Links
    • Order Info
  • REQUEST A QUOTE

Clay: How It's Made

8/25/2021

3 Comments

 

Ever wonder how clay is made?

STEP 1: Dry Materials
The dry materials are dumped into the clay mixer. The augur runs for a few minutes to combine the materials in their dry state.

STEP 2: Water
A predetermined amount of water is added to the mixer.

STEP 3: Mix
The augur runs for a while to ensure the ingredients are thoroughly blended. This step can take anywhere from 30-90 minutes depending on the type of clay.

STEP 4: De-Airing
Clay drops down from a hatch in the mixer and into the pugmill below. The clay is pushed through a vacuum chamber to remove all air. This stage is especially critical for quality control. You can see Juan returning clay to the back of the pugmill when the vacuum pressure drops below required levels.

STEP 5: Packaging
The finished clay is cut into 25-pound blocks by a hydraulic slicer. Then the clay crew bags, boxes, and palletizes the clay.

3 Comments

The Ceramic Process

4/21/2021

1 Comment

 
How exactly does a plate become a plate? For beginners, this process can seem mystifying and complex, but the basic steps for making a ceramic piece are relatively straightforward. In this lesson, we'll cover this process from start to finish to give you a basic understanding of how that lump of clay becomes a coffee mug.
Picture

Forming

There are a wide variety of forming methods, from throwing on the wheel to hand building. You can learn more about them in the lesson: Methods of Making. For the purpose of this lesson, we'll just define this stage of the process as the 'wet stage'. The artist takes a lump of moist clay and shapes it into the desired form, whatever that may be.

Drying

Once the piece is shaped, it must be allowed to dry completely. This process can take anywhere from a few days to a few weeks, depending on the size of the piece and the humidity of the environment in which is is left to dry. All of the water must leave the clay before it can be fired. This is because water turns to gas at 212° F. Water expands during this phase change, so if there is any still trapped in the clay body, it will cause the piece to crack or explode in the kiln.
Picture
Picture

Bisque Firing

Once the piece is completely dry, it is put into the kiln and fired. This first firing is called the bisque firing. While bisque firing temperatures can vary slightly, the vast majority of artists will bisque at cone 04, which is around 1950° F. During this firing, the clay goes through a structural shift that hardens the clay into a more durable form.

Glazing

Once the piece has been bisqued, it's time to apply the glaze. You can learn more about glazes in the lesson: Glaze 101. The glaze is a layer of glassy material that gives color and finish to the piece, once fired.
Picture
Picture

Glaze Firing

The second firing is called the glaze firing, and is usually the final step in the ceramic process. Glaze firings vary in temperature depending on the clay and glazes used. During this firing, the glaze matures (goes through a chemical change to become the desired finished product). If a stoneware or porcelain clay is used, the clay also matures during this firing.

Enjoy!

Once they come out of the glaze firing, most pieces are considered 'done', but there are instances where additional firings or finishing treatments might be applied. Gold luster, for example, requires an additional firing after the glaze has been matured. Many potters sand the bottoms of their pieces to smooth them and prevent scratching the table surface. Some artists apply more layers of glaze and re-fire multiple times to build up complex surfaces. Most often, though, this is where the process ends.
Picture
1 Comment

Glaze 101

4/5/2021

2 Comments

 
Picture

What's In a Glaze?

  • Silica: This is the bulk of the glassy substance we usually think of when we think about glaze.
  • Flux: This is a chemical that lowers the melting point of the silica, enabling it to react at ceramic temperatures rather than the much hotter temperatures it would otherwise require.
  • Clay: Yes, really. This forms a sort of base substrate for the rest of the glaze ingredients and also helps stabilize the melting temperature of the glaze. Opaque glazes like shinos contain higher percentages of clay in their recipes. Not every glaze recipe will contain clay, but will have some other type of refractory (heat-resistant) material instead.
  • Colorant: This is what gives the glaze it's color. Metal oxides like iron, copper, and cobalt are a few common ones. Colorants can be used in various quantities and combinations to achieve different results.
John Britt has a great analogy for this. Here's a short video excerpt of him explaining the basics of glaze structure.

Types of Glaze

Glaze

The term 'glaze' can be used as an umbrella word to encompass all fired finishes, however it more accurately refers to a product that produces a finished result on its own, without needing additional products (like a clear glaze). Commercial glazes are typically divided into two categories based on their firing range: cone 04/06 (low-fire) and cone 5/6 (mid-fire). They can also come in a variety of finishes (matte, gloss, textured, etc), and with an endless range of colors. Glazes are applied to bisqueware (clay that has been through the preliminary firing), and can be used on their own or layered with others to create interesting effects. There are many different sub-categories of glazes such as crystalline glazes, shinos, raku glazes, and celadons.

Underglaze

Underglazes are clay-heavy formulas that are very opaque and stable. One way to think about them is that they are the 'color' without the 'shiny' built in. Because they are so stable, they are often used for detailed paintings and delicate line work. They can be applied to greenware (clay pieces that have not yet been fired) or bisqueware, over or under other glazes.

Luster

Also called 'overglazes', these are a special type of fired finish that requires an additional firing after the glaze firing. Gold luster is probably the most common type of overglaze, though there are other options such as Mother of Pearl. These specialty finishes are fired to much cooler temperatures than most glazes (usually in the 019-016 range).

Choosing the Right Glaze

The most important consideration when picking out your glazes is the firing range. It is critical to match your glazes to your clay body. If you are working with low-fire clay, you will want to pick low-fire glazes. For mid-fire clay, choose mid-fire glazes. If you are taking classes at a community studio that uses high-fire clay, they will usually provide you with several glaze options that are formulated for their firing temperatures. Ask your instructor before bringing in outside glazes to use in their kilns.

Some low-fire glazes do well at mid-fire or even high-fire temperatures, but the pendulum does not swing the other direction. If you fire mid-fire glazes to low-fire temps, they will not mature. Instead of looking shiny and colorful, they will be chalky and dull. You also don't want to over-fire a clay body to accommodate a higher-temperature glaze. Over-firing clay can cause it to crack, melt, and/or stick to the kiln shelf. For beginners, we strongly recommend just picking a firing range and sticking with it for a while. Later on, after you've gotten your feet wet, you can start to branch out.

Applying Glazes

Brushing

Nearly all commercial glazes are formulated for a brush-on application. To apply a brushing glaze, shake the bottle vigorously to mix the contents before opening. Wipe your bisque piece with a damp sponge to remove any dust. Apply 2-3 coats of glaze to the bisque surface, allowing each coat to dry in between. The first coat will take only a few minutes to dry. The second will take much longer (about 20 minutes). Be patient! The application should be fairly thick, like applying BBQ sauce to a rack of ribs. Alternate the direction of your brush strokes between coats. Most commercial glazes require 3 coats, but check the label to verify before you start. Some glazes, like clears, need fewer coats. Always read the application instructions on the bottle before beginning to glaze.

Dipping

If you've taken a class in a high-fire studio, you've probably encountered this method of glaze application. Dipping glazes are typically mixed in large batches (3-5 gallons) and stored in lidded buckets. To apply dipping glaze to your piece, stir the glaze thoroughly to re-mix the ingredients. Apply wax resist to the bottom of your bisque piece to repel the glaze. Once the wax is dry, use your fingers or dipping tongs to submerge your bisque piece in the glaze bucket for 2-3 seconds. Remove the piece and allow excess glaze to drain/drip off the piece and back into the bucket. Once the dripping stops, set the piece aside to dry. Clean up the waxed bottom and any unwanted drips with a damp sponge.

Spraying

Spraying glazes requires specialized equipment, most importantly a properly-rated respirator. Airborn silica dust is harmful to your lungs and should not be inhaled. To achieve an even application of glaze, place your piece on a banding wheel inside the spray booth or other designated area. Fill your spray gun with dipping glaze. Brushing glazes are too thick for this method of application. Commercial underglazes can be thinned with water for use in a spray gun, however be aware that you may need to apply an extra coat or two to achieve full opacity.

To apply the glaze, turn your piece on the banding wheel slowly, spraying glaze in quick, even passes side-to-side until the entire piece is coated. Heavier application will result in drips of glaze, which may or may not be your intent. Multiple coats are needed to achieve full coverage. Spraying glazes is a very gestural method and can provide a wide range of results depending on the artist wielding the spray gun.

Layering Glazes

Once you have a grasp of the basics of glazing, you might want to experiment with layering. By placing a few layers of one glaze atop a few layers of another, you can get a result that is wildly different from either one of the glazes individually. This is because the glazes contain chemical components that interact with one another during the firing. Independently, they may act one way, but when combined with each other, they create something new.

Though many commercial glaze manufacturers test glaze combinations and publish recommended layering guides, layering glazes is a relatively unpredictable process. It's important to approach this technique with an open mind and no expectations. Also be aware that combining glazes often means they will run/flow more during the firing, so it's a good idea to place a bit of scrap kiln shelf beneath your experimental pieces.
2 Comments

Clay 101

3/30/2021

0 Comments

 
Picture
Ceramics is an ancient art form that dates back to mankind's earliest ancestors, the skills and traditions passed down through countless cultures over millennia. All around the world, you can find artisans practicing methods from hundreds (if not thousands) of years ago. Clay is a medium of both necessity and expression that links humanity, defying borders and spanning generations.

And anyone can do it.

Many beginners we encounter have experienced clay in a high school or college art class, but if you have never touched clay before (or have simply forgotten what you learned in the past) don't let that stop you! A few simple rules and guidelines can get you started. In this lesson, we'll cover some basics that can help you dive right in, even with zero experience.

Foundations

Let's start with the core concepts of working with this material.

1.  Clay is water-based.

​This means it will dry out over time when exposed to air. Keep your unused clay wrapped up tightly in its plastic bag. A spritz of water will restore some moisture to the clay if it begins to get too dry. If you want to save an in-progress piece for later, make sure to wrap it up between sessions.

2.  Work on a porous surface.

Materials like canvas, plywood, newspaper, and even old sheets can keep the clay from sticking to your table as you work.

3.  Keep your clay pieces no more than the thickness of your thumb.

This will allow the clay to dry and fire properly. Want to make a big sphere? Just hollow out the inside!

4.  Tools are only limited by your imagination!

Anything can be a tool! Explore your home to find interesting textures and objects that can be used as tools. Doilies, jewelry, and kitchen utensils are a great place to start! Just wash your makeshift tools in the laundry or dishwasher when you're done.

5.  Clay is non-toxic and must be fired to be made durable.

This requires extreme temperatures of over 1800° F. Unlike polymer clays (like Sculpey), putting pottery clay in the oven for a few hours won't do much. Want to keep your clay creation forever? Armadillo offers firing services!

Types of Clay

There are three main types of water-based clay:

Earthenware

This is a very open clay body that is often used to make planters due to the fact that it remains porous (water can pass through it) after firing. Earthenware can be used for functional work, but must be glazed in order to hold water or be food-safe.

Stoneware

The most common choice for those wishing to make functional ware. Stoneware is durable and easy to work with, and vitrifies (becomes mostly watertight) when fired to the appropriate temperature, making it ideal for dinnerware.

Porcelain

Denser than stoneware, porcelains are made from finer base materials that contribute to a tightly-knit molecular structure that provides both durability and a smooth working surface. Porcelain is more challenging to work with than earthenware or stoneware.
Picture

Attachments

Want to put a handle on that cup or some ears on that dog you sculpted? Attaching two pieces of clay together might seem like a no-brainer, but there are a few critical details to get right if you don't want your dog's ears to fall off during the drying process.
  • Moisture: Make sure both pieces are at a similar stage of wetness. Don't attach a fresh piece of clay to a piece that's already half-dry.
  • Score and Slip: Before attaching the two pieces, scratch up the contact surfaces with a fork or toothpick. Dab a few drops of water or vinegar onto the scratches, then scratch again for good measure. This creates a slurry of wet clay that acts like glue.
  • Press Like You Mean It: You're not adding garnish to a supper plate. Press those pieces together with gusto! A slight twisting motion helps, too.

Drying

Once the piece is finished, it needs to dry completely before it can be fired. Simple shapes like cups, bowls, and trays can usually be left out in the open to dry, however if you have any delicate attachments or uneven thickness in various parts of the piece, it is best to dry it slowly. Drape a sheet of plastic (like a trash bag) loosely overtop the piece. This allows some fresh air to reach the clay, but at a lesser rate than if you left it completely uncovered. After a few days, remove the plastic and let the piece finish drying in the open. It is best to dry clay pieces on a flat, porous surface.

Clean Up

Tools and work surfaces can be cleaned with a sponge and water, and soap if needed. Clothes that get clay on them can be washed right along with the rest of your laundry, though you'll want to knock any large clumps off first. Clay can clog drains over time, so don't put a big chunk down the kitchen sink! Scrape as much off of your tools as possible before washing. Whenever sweeping up dry clay, be sure to wear a properly-rated respirator and ventilate the space as well as possible.

Ready to dive in?

Here are a few helpful links to get you started on your clay journey!
Picture

Learn about our
Firing Services

Learn More

Clay Play Kit: Basics for Beginners

$35.00

Sold out

Shop
Picture

Grab a book to learn more about working with clay

Browse Books
0 Comments

Methods of Making

3/19/2021

0 Comments

 
Picture
When it comes to working with clay, the possibilities and techniques are virtually infinite, but there are a few core techniques that should be familiar to any potter. In this lesson, we will take a look at some basic methods and terminology that can help you get a foundational grasp on the different approaches to creating objects out of clay.
Picture

Throwing

A potter's wheel is often the first thing people think of when they think of ceramics. Thanks to the 90's film Ghost, those imaginings may or may not include Patrick Swayze or Demi Moore. Throwing on the wheel is still an extremely popular method thanks to the speed and consistency with which a skilled potter can produce work. However, this approach is just that - a learned skill - and can take years of diligent practice to master. Don't let that scare you off, though! An absolute beginner can expect to be able to produce at least a rudimentary vessel over the course of an 8-week class.
Picture
TERMS TO KNOW
  • Thrown-and-altered: A wheel-thrown piece that is cut into, distorted, or added to, altering its geometry to something other than cylindrical.
  • ​Off the hump: A large ball of clay is centered on the wheel, with small amounts being pulled up, formed, cut off, and set aside. An efficient way to make many small pieces in a single session.
  • Sectional: A tall piece made by throwing several contiguous sections and then attaching them one atop the other to form a piece that is larger than the potter would otherwise be able to create.
Picture

Hand Building

Hand building is exactly what it sounds like: building a piece with your hands. This may seem like a silly misnomer - after all, you use your hands when you throw on the wheel - but the term refers more to the primary tool with which you are making the piece: your hands.

Like throwing, hand building is a skill that takes years of practice to master, however it is much more accessible for beginners and requires very little upfront cost.

There are a huge number of approaches to hand building, covering a wide range of forms. Sculptures, tiles, and functional ware can all be created through variations of this process, and there are far too many methods to list here, but we will cover a few popular terms you might come across when learning more about hand building.
TERMS TO KNOW
  • Slab building: An approach that uses broad, flat sections of clay to construct a piece. This method can be split into two major categories, hard slab and soft slab construction. Hard slabs are stiff and are used similar to how a carpenter uses wood boards. Soft slabs are still very pliable, and can be shaped and stretched during and after assembly.
  • Armature: In sculpture, this is a structural aid on which a piece is built. It can be made from wood, wire, newspaper, or foam, and provides support to the piece during construction. An armature is typically removed before the firing process.
  • Pinch pots: Often the first project taught in any beginning clay class, this method of making a pot utilizes a pinching technique to hollow and thin a ball of clay into a rudimentary vessel shape.
  • Hump/slump molds: Forming aids typically used with slabs to create a desired shape. Hump/slump molds can be made from plaster, wood, or even bisqued clay. A slab is draped over (for hump) or into (for slump) the mold and allowed to stiffen up so it retains the mold's shape.

Slip Casting

Popular with mass production facilities, slip casting is the method of pouring liquid clay (slip) into a plaster mold to create a form. Unlike hump/slump molds, slip molds are mostly enclosed with the negative space inside creating the shape of the piece. The porous plaster draws water out of the slip, creating a "skin" of solid clay that grows the longer the mold is left to set. Once the desired thickness is achieved, the remaining slip is poured back out of the mold, the mold is opened (after a short waiting period), and the piece is removed.
Picture
This may seem like a quick and efficient way to produce consistent ware, but many people underestimate the amount of time and energy that goes into the setup of this process. While many commercial molds and casting slips are available, venturing into custom territory involves learning about plaster, slip formulation, and multi-part mold making, which is an art form in and of itself. That being said, a beginner who is not picky about shapes can often find used slip molds for sale locally (Craigslist or estate sales) at inexpensive prices, and commercial slip itself is not terribly expensive. Armadillo makes two low-fire casting slips right here in Austin, and offers several mid-fire options as well.
TERMS TO KNOW
Slip tank: A large storage container designed specifically for slip. They often have dispensing nozzles and a mixing apparatus called a blunger incorporated into the design.
Mold bands/straps: Large rubber bands or ratchet straps used to keep the pieces of a multi-part mold together while slip is poured into it.
Deflocculant: A chemical added to slip formulas to reduce viscosity, helping the component materials stay in suspension while also making the slip pour more smoothly. (Commercial slips already have this chemical added.)
While nearly all approaches to working with clay fall into one of these three broad categories, there are always outliers. This is nowhere near a comprehensive list. The number of hand building techniques alone could fill several dictionary-length books. Exploration lies at the heart of ceramics, and we encourage you to dig deeper into the methods that inspire you. Keep learning, keep discovering. The rabbit hole goes on forever.
0 Comments

Clay Tools

3/17/2021

0 Comments

 
One walk past the tools section at Armadillo Clay may leave your head spinning. There are hundreds of options, all shapes and sizes of every tool type imaginable. While there may be no end to the variety of clay tools on the market (and more are being invented every day), there are some basics that appear fairly consistently in any studio.
Picture

Cutoff Wires

This is probably the first clay tool you ever used. Cutoff wires allow you to cut chunks of clay from the block with ease. When throwing on the wheel, this is the tool you use to separate the finished pot from the bat or wheel head. With a steady hand, they can also be used to cut facets in the outside of a soft piece.

Needle Tools

A toolkit staple, needle tools can be used for all sorts of applications, especially when throwing on the wheel. The sharp point can remove an uneven rim, score a guide line, pierce air bubbles, draw surface designs, and even be used as a scoring tool in a pinch.
Picture
Picture

Ribs

This term refers to any broad, flat pottery tool. Ribs can come in many different shapes and sizes, and be made from a number of materials including wood, metal, polymer, rubber, and plastic. Even chunks of coconut shells can be used as ribs! Ribs can be rigid or flexible, with smooth or serrated edges.
​
Most often, ribs are used to shape pieces being thrown on the wheel, but they also have many uses in hand building. Ribs can be used to smooth slabs, compress seams, and even stretch and form pieces just like on the wheel.

Loop Tools

Loop tools are just what they sound like: a tool made from a loop of wire. This wire can vary in thickness and be bent into an endless variety of shapes. Loop tools are typically used for removing clay during decorating and sculpting, but can also be used as trimming tools on the wheel.
Picture
Picture

Ribbon Tools

Ribbon tools look a lot like loop tools, with one major difference. Instead of wire, the tool end is made from a flat piece of metal. Usually the edges of this metal are beveled and sharpened, but not always. Ribbon tools cut through clay more easily than loop tools, and are more often used for trimming on the wheel.

Calipers

Calipers come in two main styles: single-ended and double-ended. They are used to measure and compare things like rim sizes. Double-ended calipers can be used to convert interior measurements to exterior ones, which is useful when making lidded forms. Calipers can be made from wood, metal, or plastic.
Picture
Picture

Wood Tools

Wood tools are probably the most varied of all clay tools when it comes to shape. The different styles are endless, from rounded sculpting balls and pencil-like points to tapered blades and flat wedges.
​(Right) One common shape of wood tool is called a potter's wood knife. This is a blade-like end that comes to a sharp point, and is a core tool in many ceramists' kits, especially those who throw. The wood knife can be used to bevel the bottom edge of a pot on the wheel, cut slabs for hand building, or to scratch designs into the clay surface.
Picture
Picture

Finishing Tools

These rubber-tipped tools are great for cleaning up seams after attachments are made. They can also be used in sculpting or as a stylus for decorative marks or signing pieces.

Scoring Tools

Scoring tools come in many different styles. They are used for scoring the clay prior to making attachments. The only prerequisite for a scoring tool is that it has some sort of coarse edge that can make scratches in the clay surface. Most students start out using a serrated metal rib as their scoring tool, but other options exist that are smaller and more precise. Kemper offers several that are made from groups of wires crimped onto a handle. Other companies make retractable versions that keep you from accidentally poking yourself.
Picture
Picture

Sponge Sticks

(Left) Also called 'sponge-on-a-stick', these are used to remove excess water from the inside of a pot when throwing on the wheel.

Throwing Sticks

(Right) These extra-long tools are used to belly out pots from the inside when the neck of the pot is too narrow to fit your hand or the pot is too tall to reach easily.
Picture

Fluting Tools

These are a style of cutting tool that is specifically designed for a decorative technique called fluting. Fluting is basically carving repetitive sections of clay out of the surface of a piece. Fluting tools are designed to help you cut consistently without digging too deep into the clay. Different blade shapes can provide a variety of looks.
Picture
Picture

Paddles

Paddles have a number of uses. They can be used by hand builders to compress seams or flatten areas. When throwing on the wheel, they can be used to form the finished pot into a more geometric shape. Textured paddles can be used to apply surface design quickly to a soft pot.
Picture

How many tools do I really need?

A common tendency, especially with beginner-to-intermediate clay hobbyists, is to accumulate dozens upon dozens of tools. The idea behind this trend is the thought (conscious or otherwise) that if only we could find just the right tool, our pots would be so much better! In reality, the only way to make better work is through practice. Lots and lots of practice. While having the right tool for the job is important, there comes a point in time where we must pause and remember that age-old saying: It's a poor craftsman who blames his tools.

Challenge yourself. Pick a limited number of tools to work with and stick to them. By forcing yourself to make do with only 8 or 10 tools in your kit, you'll find yourself innovating new ways to use them and identifying exactly what it is you need in a particular tool.
This is by no means a comprehensive list. There are countless tools out there in the clay world. In the end, a tool's uses are limited only by your imagination, and just about anything can be a tool.
​Don't be afraid to experiment!
0 Comments

Kilns and Firing

3/12/2021

0 Comments

 
Many teaching studios focus solely on the making part of the ceramics process and never expose their students to the loading and firing of kilns. While the reasoning behind this is perfectly sound (one mistake can ruin an entire kiln load of work!), this exclusion leaves many fledgling ceramists with a massive hole in their clay education. In this lesson, we'll cover some basics about kilns and firing to fill in some of those gaps.

Please note: To best understand this lesson, it is important to have a decent grasp of the pyrometric chart. If cones are still a mystery to you, we recommend taking a look at the Cones: Explained lesson before reading further.

Types of Kilns

Electric Kilns

The most common type of kilns out there are electric kilns. These are just what they sound like: a kiln that uses electricity to produce heat via coils of special wire called elements that line the inside of the insulated chamber. Modern electric kilns are capable of reaching temperatures up to cone 10, though they are most often used for low- and mid-fire temperatures (cone 06-6). Even studios that run gas kilns (more on those next) will have electric kilns in-house for bisque-firing purposes.
Picture
Picture

Gas Kilns

Most universities and teaching studios use gas kilns for their glaze firings. These typically consist of a large square chamber and a tall chimney at the back. Natural gas or liquid propane is injected into the chamber through burners that mix the fuel with oxygen. The flames produced by this fuel are what heat the inside of the kiln.
Picture
​​Gas kilns can be purchased commercially through manufacturers like Bailey Ceramics, and feature digital controllers that make firing hassle-free. Many gas kilns, though, are homemade by experienced potters who prefer a bit more hands-on approach. These kilns are monitored using a pyrometer to keep tabs on the temperature and adjusting the gas and reduction level (more on that later) manually. ​Gas kilns are usually fired to cone 10, but can be used for low- or mid-range firing as well.

Picture

Salt & Soda Kilns

Gas kilns can be modified for use as salt kilns or soda kilns, and sometimes as both in one. Portholes are created in various spots all around the kiln, allowing for a liquid mixture of sodium chloride (for salt) or sodium carbonate (for soda) to be sprayed into the firing chamber. These chemicals vaporize in the high heat and react with the clay, slips, and glazes to create unique aesthetic effects. You should always wear protective gear and a properly-rated respirator when injecting salt and soda.
Picture

Wood Kilns

One of the most beloved firing processes is wood firing, a time-honored traditional method that uses wood as its fuel source. A fire box - a combustion chamber at one end of the kiln - is constantly stoked for days (if not weeks) to gradually bring the kiln up to temperature. As the wood burns, ash is produced and travels through the kiln on its way to the chimney, sticking to the pots and creating beautiful, glassy surfaces, colorful flashing effects, crystal growth, and interacting with glazes in unique ways. The longer the firing, the more ash can build up. For this reason, some wood firings can last a week or more, though a day or two is much more common. Depending on the size, these kilns can take over a week to cool. They are typically fired to cone 10-12.
Picture
Given the immense amount of work that goes into this process, both in preparing copious amounts of wood and the long hours spent stoking and monitoring the kiln, wood firings are typically a community event. Participants work in shifts under the direction of one or two firing masters who are familiar with the kiln and experienced in the wood firing process. Every wood kiln fires slightly differently, and every firing produces different results.

Alternative Kilns

While the above-mentioned kilns are the most common, they are not the only options. Kilns come in all shapes and sizes, with all manner of firing processes in mind. Experienced potters can get incredibly creative with their kiln-building. The "Glo Worm" pictured here is a temporary kiln (constructed for the firing and then broken down immediately after) that makes a periodic appearance down at the Eye of the Dog Art Center in San Marcos. It is built mainly of kaowool (ceramic fiber blanket), wire mesh framing, and an old barrel for the fire box, though salvaged electric kiln sections have sometimes been used in past years.

These alternative kilns can be a fun challenge, but always keep in mind that you are dealing with extreme temperatures that can cause 3rd degree burns in seconds. Appropriate safety measures should always be in place before attempting to build or fire any kiln, but these precautions are doubly important when dealing with alternative kilns and firing processes.
Picture

Oxidation vs. Reduction

You may have heard these terms in passing or noticed them on our cone 10 clay listings, but what exactly do they mean? Simply put, the when it comes to ceramics, 'oxidation' and 'reduction' refer to the oxygen content of the atmosphere inside the kiln during firing.

Oxidation

This term means that there is free oxygen inside the firing chamber throughout the firing process. Though it is possible to fire a gas kiln in oxidation, usually this term is used when discussing electric kilns. Since there is no fuel in an electric kiln to consume the oxygen inside the chamber, there is usually plenty of oxygen floating around in there.​ Therefor, you may hear the word 'oxidation' used interchangeably with 'electric' when discussing discussing kilns or firings.
Picture

Reduction

Reduction is the process of starving the firing chamber of oxygen during a firing. This requires the use of combustible fuels as a heat source, which just means 'flames'. Any kiln besides an electric kiln will meet this requirement. This oxygen-deprived atmosphere causes unique and sometimes dramatic reactions in clay bodies and glazes.

To achieve reduction, the burners and damper (a mechanism used to partially close off the chimney) are adjusted to maximize the efficiency of combustion. When a kiln is in reduction, you will often see flames shooting out from the top of the chimney. This is because the flames have consumed all available oxygen within the chamber and are forced to seek oxygen elsewhere. While it is possible to fire a gas or wood kiln in oxidation, it is far more common to aim for at least some level of reduction.

Other Types of Firings

Raku

This could easily fit under the "Kilns" portion of this lesson, but the design of raku kilns varies so widely that it is more helpful to talk about it as a firing process rather than a kiln type.

While firing relatively slowly is usually best for the work being fired, raku contradicts this entirely. The pots are heated quite quickly in a kiln, usually bringing them up to around 1800F to mature any low-fire glazes that may have been applied to the surface. Once at temp, the kiln is opened and the pots are removed while still glowing and deposited into a reduction bin. This is a fire-proof container (like a metal trash can) filled with combustible materials such as sticks, leaves, wool, paper, etc. When the red-hot ceramic piece touches these materials, they immediately catch fire. By closing the lid of the container, you starve the atmosphere inside of oxygen, resulting in heavy reduction.

The raku process has many variables and the results of these firings can range from brilliant metallics to elegant crackle effects depending on the glazes and combustibles used. Any pottery clay can be fired in raku, but the thermal shock can cause cracks in dense bodies like porcelains. More open bodies (ones that contain grog or sand) or clays that are formulated to resist thermal shock (like Armadillo Clay's Raku body) will have a better chance of surviving this process without cracking.

Protective equipment is imperative. Leather welding gear, kevlar gloves, raku tongs, and a heat-resistant face shield should all be employed to keep you safe from the extreme temperatures. We do not recommend this process to novice potters without direct, experienced supervision. Raku-fired work is typically not food-safe.
Picture
Picture
Picture

Pit, Smoke, & Barrel

Pit, smoke, and barrel firings are fun experimental processes that can be achieved without much upfront investment, however (like raku) the results are typically not food-safe. These rudimentary 'kilns' can be made from old BBQs, steel barrels, or just pits in the ground. They don't get hot enough to mature the clay or glazes, but you can achieve a number of interesting effects by experimenting with the types of combustibles you add or extending the length of the firing.
At its most basic, a kiln is just a box of fire, but the sizes, designs, and fuel sources are virtually endless. Electric is easy, safe, and reliable. Other fuels are a bit more involved, but can produce unique, truly one-of-a-kind results. Through classes, research, and experimentation, you can experience many of these methods for yourself and add to your ceramics knowledge over time.
0 Comments

Cones: Explained

3/11/2021

1 Comment

 
Picture
​When selecting a clay body or glaze, you will most likely see reference to its “cone” range. For example, Balcones White is a 'cone 10 clay'. But what does this even mean? In this lesson, we'll take a look at cones, the pyrometric chart, and help you get a basic understanding of what they are and how they fit into the ceramic process.

​What is a cone?

A cone (technically a pyrometric cone) is a physical object in the shape of a tall pyramid that serves as a visual tool for measuring heat work. When heated, the cone will begin to bend and eventually melt within a specific temperature range. Cones have a number assigned to them, typically 022-14 for ceramics, and thus a different chemistry for each number. Although there is a temperature related to each of these numbers, it is often presented as a range rather than one specific temperature. This is because heat work is dependent on time as well as temperature. A kiln fired quickly will require a higher peak temperature than a kiln fired slowly to bend the same cone. The chart to the left (click to enlarge) is split into three columns. You will notice that the temperature listed in the "Slow" column is lower than the ones listed for "Medium" or "Fast" firings. This is heat work in action.

​Modern kilns have come a long way. Today most electric kilns are controlled by a computer that interprets temperature via a thermocouple, a probe that translates heat into an electric current that is then translated into a specific temperature. Since the computer only reads the temperature and not heat work, an average temperature for each cone is used. Although digital kilns are very reliable it doesn’t hurt to double check with witness cones every now and then. You may find it necessary to put a hold on your kiln (maintain the peak temperature for a short time rather than shutting off immediately) in order to fully bend the cones.

Since their invention in 1892, pyrometric cones are still the most reliable indicator of the heat work achieved by your kiln.

4 Types of Cones

Picture
There are 4 different types of cones available.

Bars: These are used in a kiln-sitter type controller. When the kiln reaches the target temperature, the bar bends and triggers the kiln to turn off.

Small Cones: Also known as 'sitter cones'. They serve the same purpose as bars.

Large Cones: These are the traditional witness cones (for 'witnessing' the temperature of the kiln as it climbs). They are used to monitor heat inside the kiln.

Self-Supporting Cones: Witness cones with a broad base, eliminating the need for a cone holder. They serve the same purpose as large cones.

Using Cones in Firings

Technology is great. Thermocouples, pyrometers (handheld temperature readers), and digital controllers have made monitoring your kiln's firing easier than it ever was in the past. There are plenty of scenarios, however, where you may want to use cones to verify that you hit the proper temp or just get more detailed information about how your kiln is performing. Potters do this by including cone packs in their firings.
Picture
A cone pack is a set of witness cones placed in a holder. This holder can be something as simple as a lump of clay (just make sure you let the clay dry completely before firing the kiln!). A cone pack typically contains 3 or more cones at and around the target firing temperature. These packs are placed directly in front of peepholes so they can be monitored throughout the firing.

Guide Cone: This cone traditionally acts as a guide to signal that the kiln is almost up to temp. It is usually one cone below (cooler) than the target temperature.

Firing Cone: This cone matches the target temperature for the firing.

Guard Cone: This cone serves as a warning that the kiln has gotten too hot. It is usually one cone above (hotter than) the target temperature.

For electric kilns, these packs can be placed anywhere throughout the kiln and checked after the firing is complete to glean useful information about hot and cold spots in the kiln.

Do I really need to know all of this?

No. You don’t need comprehensive knowledge of pyrometric temperatures and the reactions that go on in clay and glaze, but you do need to know what you are working with. Clays and glazes fall into 3 main ranges:
  • Low-Fire (cone 06-04)
  • Mid-Fire (cone 5-6)
  • High-Fire (cone 10+)
Notice there is a “0” in front of the numbers for low-fire clay/glaze. That is not to be ignored! A good rule to remember is “the “0” means low”. You must say “Oh” if it is present. Cone 6 is about 400 degrees hotter than cone 06! As you can see from the pyrometric chart (above), the “0” serves as a negative sign. Therefore cone 05 is cooler than cone 04 whereas cone 5 is hotter than cone 4.

For the most reliable results, it is best to match your clay with your glazes. If your clay’s recommended firing temperature is cone 06-04, then you should use low-fire glazes. These may say on the label something like “apply to shelf cone 04 bisque and fire to cone 06-05”. This means your clay has already been fired to cone 04 without glaze (bisque fired). Once glaze is applied, you will then fire the piece again to cone 06-05. If the label says fire to cone 5-6, do not use on low-fire clay! Remember the zero is important! At low-fire temperatures, a mid-fire glaze will not melt. At mid-fire temperatures, a low-fire clay could warp, slump, bloat or even melt. Of course there are exceptions to every rule but if you are a beginner, avoid confusing yourself and stick to one cone range. As you gain experience, you can experiment with different temperatures for a given clay or glaze, but remember it is exactly that: an experiment. Results will vary. Experimenting requires testing and a tolerance for failure. Usually this failure will only result in an unattractive pot, but it could ruin your piece and/or kiln shelf.
​If you are new to clay you will encounter a lot of terminology that is unfamiliar, even confusing. Just remember: 'cone' is a measurement of heat and whether or not there is an “0” in front is very important. Good luck and happy firing!
Download an Orton Cone Chart Poster
Download an Orton Cones-and-Firing Guidebook
1 Comment

Coloring Clay

3/1/2018

0 Comments

 

The Limitless Possibilities of Mason Stains

​At the back of the showroom at Armadillo Clay, there lives a rack of small packages of Mason Stains. The rainbow of powders is eye-catching, but what are they even for? Though they draw many a shopper's eye, their uses can be somewhat of a mystery.

​So what are they? Mason Stains are specially formulated combinations of colorants that create specific hues. For example, #6371 Dark Teal is made up of aluminum, cobalt, and chromium. The resulting combo-colorant is a deep, rich, ocean teal that is powerful in small amounts.

But how do you use them? Mason Stains can be used in a variety of ways! Because they are colorants, they are very flexible in their applications. Here are the four most common uses:
Picture
Picture
In Clay
Wedge stain into your clay to make it whatever color you want! White clay works better as a base, and will help keep your stain color brighter. Wear gloves to avoid staining your hands! Pro Tip: Mix your stain with a little water, and then add it to your clay to make the color distribute faster and more evenly when wedging.
​

Photo from Ceramic Arts Daily and Naomi Lindenfeld
Picture
In Slip
Just like your clay, you can dye your casting and surface slips with mason stains to get custom colors! These colored slips can then be used for marbling, surface decoration, carving, and more. You can also use it for colorful sgraffito and mishima!
Picture
​In Washes
Add your stain of choice to some water, and a bit of Frit or Gerstley Borate as a binder, and you've got a brightly colored ceramic wash you can use in the same way you would use an iron oxide wash! These can also be used to do photocopy transfers.
Picture
In Glaze
If you have dabbled in glaze mixing, this one will come as no surprise to you. If not, don't worry. You can add mason stains to almost any clear or white base glaze to make it your own custom color! As with any glaze formulation, this process requires some testing to ensure a good glaze fit, and avoid undesirable surface defects. Further reading is encouraged when pursuing this application:
John Britt article in Ceramic Arts Daily
DigitalFire article on formulating and trouble-shooting
At the end of the day, using mason stains requires a bit of testing, no matter what application you are pursuing (some less than others). Each different stain has its own properties, and some colors are more powerful than others. You may only need 2% (by dry weight) of Sage Gray, but 15% of Titanium Yellow to achieve the same level of saturation for each color. And those are just slip colorant percentages for cone 5/6. If you want to make a Titanium Yellow glaze, your percentages will be different. If you want to make a low-fire slip, again, your percentages will be different. With so many variables in the mix, it is important to take the time to test!

Testing Stains in Slip

Let's get down to the nitty-gritty of how to go about testing those colors to hone in on your target hue. We're going to explore this process through an exercise of testing one stain color in various concentrations in a decorative slip. This will provide a basic understanding of the process, which you can then build upon with other testing methods.
​​
Protect your lungs! Anytime you are working with dry materials, you should wear a properly rated and well-fitting respirator!

​Step 1: Establish Your Base

To begin, we need to identify a base slip formula. There are thousands of formulas out in the world, in books and online, so do some hunting and choose one that has a good amount of community feedback. You will want to find a white or off-white slip that is intended for your firing range. For surface slips, you will need to consider the clay body onto which the slip will be applied. Choose a stoneware slip to apply to a stoneware body, a porcelain slip to apply to a porcelain body, etc. This will help match up the shrinkage rates of the two bodies and help them fit together better, minimizing cracking. Your base recipe should add up to 100, and the colorant (Mason Stain) will be in addition to that. It's a good idea to test a few different slip formulas on your clay body before committing to one and moving forward to the next step. If all else fails, you can save your clay scraps and let them dry out. Pulverize them into a powder to get your dry slip.

Step 2: Choose a Color

It's tempting to go hog-wild and want to test every color at once, but do yourself a favor and just pick one. You can come back and repeat this process again and again. Sticking with one color at a time helps avoid mistakes, especially when you are first starting out.

Step 3: Prepare Test Batches

​Decide how many different increments of the Mason Stain you want to test. I'd recommend at least 5 to give yourself a good amount of data and allow for a wider range. For the sake of this exercise, we'll stick to 5. We need to make up 5 separate mini-batches of our chosen base slip. We don't need much for each test, so 100 grams should be plenty. We will be working at a very small scale, so precision is crucial. Make sure you have an accurate gram scale on hand. Measure out your 5 batches of dry slip in 5 separate containers.
Picture

Step 4: Add Mason Stain

Now that you have 5 containers of dry slip prepared, it's time to add the colorant. Decide ahead of time what percentages you are testing and mark your containers and your test tiles. For this exercise, we're going to test the following percentages: 2%, 4%, 6%, 8%, and 10%. This is a reasonable range for most Mason Stains, however there are some that require higher percentages. Carefully measure your stain of choice and add them to your base batches. If you have 100 gram batches, this means you would add 2 grams of stain for 2%, 4 grams of stain for 4%, and so on. If you are mixing larger batches, calculate the appropriate grams for each batch. Carefully stir each batch to combine the dry ingredients.

Step 5: Slaking and Mixing

Add just enough hot water to each batch to completely cover the dry materials. Wait a few minutes for the water to make it's way down through the dry powder, stir gently, then add more water if needed to cover the dry ingredients again. It's best to cover your batches and let them slake for at least a few hours, if not overnight. Slaking is a soaking process that gives the water sufficient time to fully saturate the dry materials. Because of the extremely fine particle sizes, this can take several hours. Using hot water rather than cold water will help expedite this process. Once the batches are properly slaked, you can mix them up. You may need to add a bit more water to achieve the correct consistency (heavy cream). Blend until smooth, then sieve with a 60 mesh screen to break up any remaining clumps of dry material. Be diligent to not cross-contaminate your test batches. Clean your mixing utensils and sieve thoroughly between each batch.

Step 6: Test Tiles

Hopefully you have planned ahead and already have some test tiles made up. If not, don't sweat it, just roll out a slab of your chosen clay body and cut out some small tiles. Make sure to stamp or scratch the percentages into the tile somewhere so you know what you're looking at when it emerges from the kiln. Apply 1-2 coats of each batch to it's matching (and well-marked) test tile, and let dry. Bisque fire, apply clear glaze to half the tile, and re-fire to maturity.
From these results, I can see that this particular red requires at least 10% saturation for a convincing red in a cone 5 slip. My next step would be to try a few higher percentages to see what deeper shades I can get, as the 10% is still a little too pink for my taste. Maybe I can get that fire-engine red at 12% or 15%. I'll just have to test and find out!
Picture

In Glaze

The process for testing Mason Stains in glaze follows the same procedures as previously discussed. Instead of dry slip batches, you will have dry glaze batches to which you will add your stain. While the initial process may be the same, there is much more room for error when formulating glazes. The chemical interactions in glaze are much more volatile than in slip, so there is a decent possibility you will run into some glaze defects along the road. Working through these issues by adjusting your recipe will take time, but you will be rewarded with a custom glaze that is all your own. Additional reading is highly recommended when pursuing glaze formulation.
John Britt article in Ceramic Arts Daily (photo below from this article)
DigitalFire article on formulating and trouble-shooting
Picture
0 Comments

Spring Cleaning

3/24/2017

0 Comments

 
Picture
Spring is Here!
With an unusually warm February come and gone, it's time to really start gearing up for spring! The official start of the season is on March 20th, but we're not waiting around to get to work in the studio! After the lull of winter, there are likely to be some chores that need doing to whip your creative space back into workable shape (I know mine is a horrid mess!), so we've made up a little checklist that might be helpful to you!
Spring Studio Cleaning Checklist
  • Vacuum out the kiln: Unplug your kiln and use a hose attachment to carefully vacuum out debris from the bottom of your kiln. Don't touch the thermocouple! Static from the vacuum can damage it!
  • Sweep the studio: Make sure to wear a respirator!
  • Evaluate clay and glazes: Check your leftover clay and glazes, re-hydrate when necessary and pitch what isn't worth saving.
  • Tidy the tools: Gather up tools from around the studio and get them cleaned and organized so you can hit the ground running!
  • Refresh linens: Wash out your apron, throwing towels, rags, etc.
Stepping into a dirty, disorganized studio can really put a damper on your creative motivations. Take a day this weekend to do some spring cleaning, and your artist within will thank you for it!
0 Comments
<<Previous
Hours
Mon - Fri      9am - 5pm  
Saturday     9am - Noon

FIND A DISTRIBUTOR NEAR YOU

Armadillo Clay & Supplies

3307 E. 4th Street
Austin, TX 78702

P: (512)385-7311
F: (512)385-1152

Sign up for our
monthly newsletter!

SUBSCRIBE

For quotes and product availability, please call us at (512)385-7311

  • HOME
  • Clay
    • Low-Fire (04-06)
    • Mid-Fire (5-6)
    • High-Fire (9-12)
    • Non-Fired Clay
    • Casting Slip
  • Glazes
    • Underglazes
    • Low-Fire (04-06)
    • Mid-Fire (5-6)
    • Lusters (017-020)
  • Dry Materials
    • Chemicals
    • Plaster
    • Mason Stains
  • Tools
  • Supplies
  • Equipment
    • Pottery Wheels
    • Ceramic Kilns
    • Kiln Parts
    • Kiln Furniture
    • Slabrollers
    • Extruders
    • Carts and Cabinets
    • Pugmills
  • Molds
  • Bisqueware
  • Books
  • Glass
    • Sheet Glass
    • Glass Frit
    • Glass Accents
    • Tools and Supplies
    • GLASS KILNS
  • SALE RACK
  • Services
    • Firing Services
    • Kiln and Wheel Repair
    • Custom Clay
    • Other Services
  • Gift Cards
  • Learning Center
  • More
    • About Us
    • Classifieds
    • COVID-19 INFO
    • Artist Links
    • Order Info
  • REQUEST A QUOTE