Understanding Pottery Glazes: Types and Application

If you’ve just started throwing pots or hand-building your first pieces, glazing can feel like the most mysterious part of the whole process. You’ve spent hours shaping your clay, you’ve dried it carefully, bisque fired it, and now you’re standing in front of a shelf of bottles and buckets wondering what on earth to do next. Don’t worry — every potter has been exactly where you are right now. Glazing is genuinely one of the most exciting parts of ceramics once you understand what’s happening, and this guide is here to make sure you feel confident rather than confused.

Glazes are essentially glass-forming mixtures that, when fired to the right temperature, melt onto the surface of your pot and fuse permanently with the clay body. They can be glossy or matte, opaque or translucent, smooth or heavily textured. They can run dramatically down a pot or sit perfectly still. Understanding why they behave the way they do — and how to apply them properly — will save you from a lot of heartbreak when you open that kiln door.

What Exactly Is a Glaze?

At its most basic, a glaze is a mixture of silica (which forms the glass), alumina (which adds stability and stops it running off your pot entirely), and a flux (which lowers the melting point so the whole thing actually melts during firing). Most commercial glazes you’ll buy ready-made from suppliers like Scarva Pottery Supplies in Northern Ireland, Bath Potters’ Supplies, or Potclays in Stoke-on-Trent already have these components balanced for you. When you’re starting out, that’s exactly what you want — a reliable, pre-tested product that behaves predictably.

On top of these core ingredients, glazes contain metal oxides and other colourants that give them their colour. Cobalt produces blues, iron gives you everything from amber to dark brown to celadon greens, copper yields turquoises and greens, and manganese creates purples and browns. The same colourant can produce wildly different results depending on whether your kiln fires in an oxidation or reduction atmosphere, which is part of what makes ceramics so endlessly surprising.

The Main Types of Glaze

Before you can choose the right glaze for your work, you need to know what the main categories are and what distinguishes them from one another.

Earthenware Glazes

Earthenware clay bodies are fired at relatively low temperatures — typically between 1,000°C and 1,150°C. If you’re using a small electric kiln at home or in a community studio, chances are you’re working in this range. Earthenware glazes are specifically formulated for these lower temperatures. They tend to be bright and vivid in colour, which is part of their appeal. Think of traditional Majolica ware or the cheerful, colourful pots you see at craft markets. They’re a brilliant starting point for beginners.

One thing to be aware of: earthenware clay bodies remain slightly porous even after glaze firing, which means any unglazed areas (such as the base of a pot) can absorb water. This isn’t necessarily a problem for decorative pieces, but it’s worth keeping in mind if you’re making functional ware like mugs or bowls.

Stoneware Glazes

Stoneware is fired at much higher temperatures, usually between 1,200°C and 1,300°C. At these temperatures, the clay body vitrifies — essentially turning into a dense, glass-like material that’s completely non-porous. Stoneware glazes are formulated to mature at these higher temperatures, and they tend to have a more subtle, sophisticated quality to them. Many potters fall in love with the earthy, natural-looking surfaces you can achieve at stoneware temperatures. If you’ve ever admired a beautifully simple, pale grey or warm brown mug, it was almost certainly stoneware.

Most community pottery studios in the UK that fire to stoneware use electric kilns set to around 1,260°C to 1,280°C. Some studios have gas or wood kilns capable of reduction firing, which creates those wonderful, unpredictable atmospheric effects. If your local studio offers reduction firing, it’s well worth trying at some point.

Porcelain Glazes

Porcelain is a refined, high-firing clay body that’s notoriously tricky to work with but produces the most translucent, delicate results. Glazes on porcelain need to be carefully chosen to complement the white clay body rather than fighting against it. Celadons — those soft, jade-like glazes — look particularly stunning on porcelain. If you’re just starting out, porcelain might be something to work towards once you’ve got more experience under your belt, simply because the clay itself demands more precision in forming and handling.

Raku Glazes

Raku is a fast-firing process where pots are removed from the kiln while they’re still glowing hot and placed into a container with combustible material — newspaper, sawdust, straw — which ignites and creates a dramatic reduction atmosphere. The results are unpredictable and unique every single time. Raku glazes are specifically formulated for this process, and many of them produce spectacular metallic and iridescent effects. Raku workshops are run across the UK and are a wonderful experience — organisations like the Craft Potters Association sometimes list events, and many independent studios run raku days throughout the summer months.

Oxidation vs. Reduction: Why the Kiln Atmosphere Matters

If you fire in an electric kiln, you’re almost certainly firing in oxidation — meaning there’s plenty of oxygen present throughout the firing. Most colour charts and glaze manufacturers’ samples are photographed under oxidation conditions. Gas and wood kilns can be starved of oxygen during firing, creating a reduction atmosphere where the flame actively hunts for oxygen and pulls it from the metal oxides in your glazes. This fundamentally changes the colours. Copper, for instance, which gives you a pleasant turquoise in oxidation, can turn a deep, blood red in reduction. It’s genuinely transformative.

As a beginner, don’t let this overwhelm you. Electric kiln oxidation results are perfectly beautiful and much more predictable, which is exactly what you want when you’re learning. Reduction is something to explore once you’ve built up some experience and confidence.

Choosing the Right Glaze for Your Project

The single most important rule when choosing a glaze is this: your glaze must be formulated for the same temperature range as your clay body. Using an earthenware glaze on a stoneware clay fired to 1,260°C will give you a completely different result from what’s shown on the tin — likely a dull, underfired surface or, at worst, a pot that cracks. Always check the cone rating or temperature range on your glaze and match it to your clay.

Beyond that, think about the effect you want. Do you want a clean, consistent covering of colour? A commercial brushing glaze is your best bet. Do you want something more interesting — maybe a glaze that breaks over texture and shows the clay beneath on raised areas? Look for a “tenmoku” style glaze or a simple iron wash over a clear base. Do you want something dramatic and runny that pools at the base? Be very careful about test firing first, because runny glazes can fuse your pot to the kiln shelf, which is an expensive problem.

How to Apply Glazes: Methods and Techniques

There are several ways to get glaze onto your bisque-fired pot, and each gives a different result. Here are the most common methods you’ll encounter as a beginner:

• Brushing: Commercial brushing glazes are specifically formulated to go on smoothly with a brush, usually in two or three coats. They contain binders that stop the glaze cracking as it dries. This is the most accessible method for beginners and gives you good control. Use a wide, soft brush and work in one direction, allowing each coat to dry before applying the next.
• Dipping: Dipping involves submerging your pot in a bucket of glaze for a few seconds. The bisqueware absorbs the water and leaves an even coating of glaze behind. It’s fast, gives excellent even coverage, and is favoured by many production potters. You need enough glaze to actually submerge your piece, which means a decent-sized bucket, but the results are beautifully consistent.
• Pouring: If you don’t have enough glaze to dip, you can pour it over your pot held over a bowl or bucket. This works particularly well for the inside of bowls and mugs — pour, swirl, and tip out the excess. Combine with brushing or dipping on the outside for full coverage.
• Spraying: Spraying glaze gives a very even, controlled coat and allows you to layer colours beautifully. However, you need a spray gun and, crucially, a proper spray booth with extraction, because inhaling glaze particles is a serious health hazard. Many community studios have spray booths. If you’re setting up at home, this is one area where you shouldn’t cut corners on safety equipment.
• Wax resist: Not a method on its own, but a technique used in combination with glazing. You paint liquid wax onto areas you want to keep unglazed or to preserve a lower layer of glaze. Wax burns off harmlessly in the kiln. It’s a great way to create patterns and decoration.
• Trailing and slip decoration: Using a slip trailer or a bottle with a fine nozzle to trail glaze onto the surface in patterns. This is how traditional slipware — the kind you see in collections at museums like the Potteries Museum and Art Gallery in Stoke-on-Trent — was decorated. It’s enormously satisfying to do.

Practical Steps for Glazing Your First Pot

Let’s make this concrete. Here’s a straightforward process for glazing a bisque-fired pot for the first time:

1. Clean your bisqueware. Wipe your pot down with a slightly damp sponge to remove any dust or fingerprints. Dust can stop glaze adhering properly. Allow it to dry completely before glazing.
2. Wax the base. Apply a thin coat of wax resist to the bottom of your pot — the part that will sit on the kiln shelf. You never want glaze on the very base, because it will fuse to the shelf during firing and you’ll either break the pot trying to remove it or damage the shelf. Leave a margin of about 5mm from the base.
3. Stir your glaze thoroughly. Glazes settle and separate in the tin or bucket. Stir right to the bottom with a stick or use a drill
   with a mixing attachment until the glaze is completely smooth and uniform in consistency. A well-stirred glaze should coat the back of a spoon evenly with no lumps or streaks. If you are using a commercial glaze that has been sitting for some time, give it a particularly thorough mix — the heavier particles, including the colourants, tend to sink to the bottom and if left unstirred you will find your results are patchy and unpredictable.
4. Apply the glaze evenly. There are three main methods: dipping, pouring, and brushing. Dipping is the most reliable for getting an even coat — simply hold the pot and submerge it in a bucket of glaze for a few seconds, then lift it out and let the excess drip off. Pouring works well for larger pieces or awkward shapes. Brushing is the most accessible method for beginners but requires multiple coats applied in alternating directions to avoid streaks. Whichever method you choose, aim for a thickness of roughly 1–2mm when wet, which typically fires down to around half that depth.
5. Allow to dry, then check for bare patches. Once your glaze has dried to a matte, chalky surface, inspect the pot carefully in good light. Any thin or missed areas can be touched up with a brush. Handle the glazed piece as little as possible at this stage, as the dried glaze is fragile and will flake off if knocked or handled roughly.

It is worth keeping a written record of every glaze you use — the specific product, the number of coats, the application method, and the clay body it was applied to. Glazes behave differently depending on the clay they sit on, the thickness of application, the temperature of the kiln, and where the piece is positioned in the firing. Two identical pots glazed in the same tin can come out looking quite different if one sat near the top of the kiln and the other near the element. Over time, your notes will become genuinely useful, allowing you to reproduce results you are pleased with and avoid repeating mistakes.

Glaze faults are common, particularly when you are starting out, and most can be diagnosed and corrected once you understand the underlying causes. Crawling — where the glaze pulls back into islands during firing — usually points to contamination or overly thick application. Crazing, the fine network of cracks that appears in the fired surface, results from a mismatch between the thermal expansion of the glaze and the clay body. Pinholes are typically caused by gases escaping through the glaze as it melts. None of these faults means a pot is ruined outright, and some, like a fine craze on a decorative piece, can even be considered desirable. The key is to treat each firing as an opportunity to learn rather than a test you can pass or fail.

Understanding glazes takes time and patience, and even experienced potters are occasionally surprised by what comes out of the kiln. The principles covered here — the composition of glazes, how temperature and atmosphere affect them, and the practical steps involved in preparation and application — give you a solid foundation from which to build your own knowledge. As you gain experience with your specific clay bodies, kiln, and preferred glazes, the process will become increasingly intuitive. Start with a small range of reliable, well-documented glazes, work methodically, and let your results guide you forward.