How To Choose Pottery Glaze

Choosing the correct glaze for your pottery can be a difficult decision. There are a number of factors that need to be considered. Here we look at the different types of pottery glaze, how they work and how you can apply them to your project.

Firing temperatures

Perhaps the biggest impact on your pottery glazes is the temperature of your kiln. There are 3 main types of glazes, defined as follows.

Low fire glazes

As the name suggests, these types of glazes are fired at a relatively low temperature in the kiln. Low fire glazes produce a depth of color but have the added advantage that the low temperature uses minimal energy in comparison to other types of glaze.

Low fire glazes are generally fired at a firing temperature of between 1828 degrees Fahrenheit (998 C) and 1945 degrees Fahrenheit (1063 C). The finish usually produces a decorative bright and vibrant color with a high glossy finish.

Generally, they are used with earthenware clay but care should be applied as the glaze can often change the colors to something unexpected.

Mid fire glazes

Mid fire glazes are normally fired at a temperature range between 2167 degrees Fahrenheit (1186 C) and 2262 degrees Fahrenheit (1239 C). Generally, this type of glaze is used with porcelain and stoneware clay body.

In general, higher temperatures create more earthy colors, where the end use is less about decorative and more about practical. Most pottery created uses a mid fire glaze, particularly if it is to be used for functional purposes, such as for food safe products.

The reason that this type of glaze is used for more practical purposes is because the glaze is more durable. Historically, this temperature of glaze could only really produce functional colors but technology has advanced for it to be able to produce a range of brighter colors.

High fire glazes

High fire glazes are fired at a temperature range in the kiln between 2280 degrees Fahrenheit (1249 C) and 2345 degrees Fahrenheit (1285 C). As with mid fire glazes, the colors have traditionally been a bit dull with this type of glaze but technology has advanced to produce brighter colors.

As the next stage up in terms of durability, high fire glazes are often used for the most durable of end-uses. Porcelain and stoneware clays are most suited to this heat of glaze.

Because high fired glaze requires such a high temperature, firing is often done in a commercial kiln. However, Soul Ceramics does offer a range of home kilns that reach the temperatures required (Cone 10 / 2350F). Check them out here.

Different types of glaze

There are many types of pottery glaze available and all provide different results, depending on your preferred finish and end-use. Below are some of the very traditional glazes that have been used throughout the world

Ash glaze

Ash glaze is made from plants or wood ash. It is used widely in East Asia and has acidic properties.

Feldspathic glaze

Made up of tectosilicate minerals and containing glazes of porcelain, this glaze comes in pink, white, brown, grey, or blue colors.

Lead glaze

Lead glaze was a highly popular form of glaze, because it produces an opaque, glossy finish. They come in both a plain form and a colored form. This type of glaze was commonly used across much of Europe and Asia but lead is poisonous and bad for the environment and so use of this type of glaze has reduced.

Salt glaze

As the name suggests, salt glaze is made up predominantly of salt. The finish produced is transluscent and glossy. This type of glaze requires a high kiln temperature.

Tin glaze

This is essentially lead glaze combined with tin oxide. It produces a shiny, opaque finish - perfect for bright pots or decorative pieces.

Alongside traditional glazes, technology has advanced to provide some modern equivalents, all of which are used widely in the world today. These include:

Earthenware lead free glazes

The lead free aspect of these glazes ensures that the process is environmentally friendly and the product can be used for food stuffs. It is the most widely used type of glaze in modern times because it is environmentally friendly and comes in an abundance of colors.

Stoneware glazes

Stoneware glazes have a wide variety of color variations. they can also be mixed to produce a number of striking types of decoration.

This includes enabling you to double-dip, mottle, pour or paint on different other glazes for maximum creativity.

Raku glazes

Raku glazes can be either powder form or liquid form. Raku glazing is good at enhancing colors to create a bright and vibrant finish.

Choosing your pottery glaze - what type of kiln?

Electric and gas kilns can often produce quite different results. Electric kilns are commonly used in a home environment as they do not require a flu or air inlet, and are also much cheaper to set up and buy. However, if you are utilizing someone else's kiln then it may turn out to be a gas fired kiln.

The difference in outcome between the two types is mainly due to the chemical process that occurs during firing. Namely oxidation and reduction. Generally, a reduction can occur in a gas fired kiln, whereas electric kilns fire in an oxidation atmosphere.

This means that electric kilns produce glazes that are bright and clean, whereas gas kilns tend to produce more earthy colors.

What are you going to use your glazed pottery for?

The end use of your glazed pottery plays a key role in which glaze you decide to use. For instance, you may want your pottery to be functional and with a surface that you can eat off, or you may want a decorative piece.

In general terms, glazes that have a matte or non glossy finish are not classed as food safe, so they are probably best avoided if you are looking to make a practical use out of your pottery.

Another consideration is the make-up of the glaze. As mentioned earlier, some glazes can contain lead, which is poisonous, so it's definitely worth avoiding lead based glazes if you want your item to be food safe.

What type and application of glaze is best from a finish point of view?

Clear glazes

Clear glazes are the preferred choice for those who just want a clean glossy finish to their piece. This is particularly a good choice if you have used a underglaze decoration, as a clear glaze will fix the decoration in place and ensure that it does not run and is waterproof. A clear glaze will help to illuminate the decoration underneath.

Dipping glaze

Applying the glaze to your pottery can also be an important consideration. Ready made dipping glaze is often sold in big quantities, and you can literally dip your entire piece into the glaze for around 3 seconds to get a nice even covering. Unless you are making huge quantities of pieces however, dipping glaze might not be economically viable.

Brushing glaze

Brushing glaze often comes in much smaller quantities. Brushing glazes tend to have a thicker consistency to make it easier to brush on the coating. You will usually need 2 or 3 coats of a brushing glaze to ensure that you have a nice even finish on the surface.

Colored glazes

There are so many choices of colored glazes on the market. You can even choose to mix several different layers of colored glazing to create some startling effects. You need to be aware that some colors will mature at a different rate to others, and could create some strange finishes.

Summary

There are a number of factors that you'll need to consider when choosing your pottery glaze. You'll need to know what you are using your final piece for, how you are going to fire it, what type of heat you are going to need and what type of finish you are going to want. You'll also need to consider how many pieces you are looking to make so that the glaze can be applied easily.

If you are looking for a starter kiln to glaze your pieces, Soul Ceramics has a range of electric kilns to choose from.

Further Reading: What Is An Underglaze? Definition And How To Use It