Introduction to Pottery Glazing

by Elizabeth Ragona. © 2025 Alabama Art Supply.

Introduction

Glazing transforms pottery into vibrant, functional works of art. Glazes can provide effects such as glossy finishes, matte textures, or dramatic crackling patterns. Beyond adding color and sheen, glazes provide protection and depth, making each piece truly unique. Whether you're a beginner or an experienced potter, understanding glazing techniques opens up a world of creative possibilities. This introductory guide explores essential methods, tips, and troubleshooting to help you achieve professional results.

Buying Glaze 

Make sure to match the firing temperature of your glazes to the firing temperature of your clay.

• Apply cone 05 glazes to cone 05 or low-fire clay 
• Apply cone 5-6 glazes to cone 5-6 or mid-fire clay 
• Apply cone 10 glazes to cone 10 or high-fire clay 

Glossy vs. Matte Glazes

Glazes have different effects on clay surfaces. In ceramics, we refer to them as gloss or matte glazes. Gloss glazes create a shiny, reflective surface. Matte glazes make a dull surface and satin matte glazes create a semi-shiny surface that is smooth to the touch.

Underglaze

Underglaze is liquid clay with colorants added to it. Since they are made of the same materials as clay they do not melt like a glaze and remain in place when fired. Underglazes (also called slips or engobes) can be applied to unfired clay (greenware) and to fired clay (bisqueware).

When applied according to the manufacturer's directions underglazes are opaque and can be used for detailed imagery. Underglazes require a food-safe approved clear or translucent glaze applied and fired over them to become sealed and food-safe.

Glazes to use over underglazes:

• HF-9 Zinc-Free Clear (for cone 5 and up)
• LG-10 Clear Transparent (for cone 05-04) 
  

Is Low Fire Glaze Food Safe?

For pieces made from lowfire clays, any surface that comes in contact with food or drink must be covered with a foodsafe glaze that has been correctly fired in order to be considered foodsafe. Look for the foodsafe symbol on labels when looking for foodsafe glazes. Even when fired, lowfire clay remains porous enough that fluids may penetrate the surface and soak into the clay.

Exploring Clay Colors

Clay comes in a variety of natural colors, each with unique properties and aesthetic appeal. From soft whites to deep reds, the color of a clay body can influence the final look of your pottery, even under glazes.  In addition to earthy tones, clay can be tinted with pigments to create a vast rainbow of colors.

Common Clay Colors

White Clay: Often used for porcelain and white stoneware. White clay is ideal for vibrant glazes and detailed designs due to its smooth surface.

Red or Terracotta Clay: This warm, earthy clay is rich in iron oxide, giving it a deep red color. It is widely used for decorative pottery and planters.

Brown Clay: Available in various shades, brown clay often has a natural, rustic appeal. It pairs well with earthy glazes.

Gray Clay: Found in many stoneware varieties, gray clay fires to a neutral tone that complements a wide range of finishes.

Black Clay: Rare and often more expensive, black clay creates striking pieces and can be used without glaze for a natural look.

Factors to Consider When Selecting Clay Colors

Firing Temperature: Different clays have specific firing ranges. Always match your clay to your kiln’s capabilities.

Texture: Some clays have added grog or sand for durability and texture, while others are smooth and refined for detailed work.

Interaction with Glaze: The clay’s color can affect how glazes appear, influencing the final result.

Basic Glazing Methods

The general process of glazing ceramics is by mixing your glazes, applying the glaze to bisque-ware, letting it dry, then finally loading it into the kiln for the glaze firing. The kiln is slowly brought up to the appropriate temperature for the silica in the glaze to melt, then slowly cooled again. This makes your pottery strong and solid, and impervious to water and the elements.

The most practical purpose of glazing ceramics is to make them food-safe and waterproof. Clay bisque-ware that has been fired once is not yet waterproof or food-safe until the glaze is applied and subsequently fired again.

How to Glaze Pottery with a Kiln

Step 1

Ensure your bisque-fired work is as clean as possible. Remove all dust before you start with a clean sponge or lightly damp cloth. If you use water when cleaning off your bisque ware, make sure your piece is completely dry before glazing.

Step 2

Mix your glazes well. Make sure that the heavier sediment, which has likely settled to the bottom of your mixing vessel, is fully mixed to ensure a smooth consistency. You can do this by hand, by mixing vigorously with a whisk for at least 1-2 minutes. Many ceramic studios attach a whisk to a drill to mix their glazes quickly and thoroughly.

Step 3

Choose how you will apply your glaze. You can either dip your bisque-fired ceramics into the glaze, pour the glaze on, or brush the glaze on.

Underglazes can be used to add color and pattern before applying a coat of glaze, which seals and waterproofs the ceramics. Underglazes contain a small amount of gum, which makes it easier to control when painting them onto your ceramics. Apply two to three coats. Make sure you wipe off any glaze from the base of your piece before setting it aside to dry.

Step 4

Fire the glaze according to instructions. Glazes are classified as either low-fire or mid-fire, and firing them at the wrong setting may cause your piece to break.

Low-fire glazes are fired at 1845 degrees Fahrenheit. Low-fire glazes are great for when you have a very specific, controlled design in mind. The resulting colors can be bright and predictable and do not melt together much.

Mid-fire glazes are fired at 2192 degrees Fahrenheit. The colors tend to have more variation and melt together to create more romantic visual effects.

High-fire glazes are fired at 2305 degrees Fahrenheit, creating a strong and vitreous ceramic. The color range tends to be more limited.

Methods for Applying Glaze

Dipping

Submerge your piece in glaze for even coverage. Ensure the glaze is well-mixed to avoid streaking. Stir thoroughly before each use and periodically during application.

Brushing

Apply glaze with a soft brush. Use multiple thin coats for consistent results. Allow each coat to dry fully before adding the next.

Pouring

Pour glaze over your piece for an organic, fluid look. Use a turntable for even distribution if needed.

Spraying

Use a spray gun for smooth, even layers, especially on larger pieces. Ensure proper ventilation when spraying.

Advanced Techniques

Layering Glazes

Wax Resist

Tips for Success

• Mix glazes thoroughly to ensure consistency. Use a drill attachment or sieve for better results.
• Test glazes on small pieces to see how they react to firing temperatures and clay bodies.
• Keep records of your glaze combinations, application methods, and firing schedules to replicate successful outcomes.

Common Glazing Issues

Pinholing: Caused by trapped air or dust. Ensure proper clay preparation and glaze application. Sand bisque-fired surfaces lightly before glazing.

Running: Apply thinner coats to avoid excessive glaze dripping during firing. Adjust firing schedules to account for glaze behavior.

Crazing: Often due to glaze-clay body mismatch. Adjust your formula or use a compatible glaze. Consider adding silica to the glaze to reduce crazing.

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