Glazing is one of the most intriguing parts of ceramic making.
A piece that looks very plain and unfinished before the kiln can be totally transformed once the glaze is applied and fired.
Color, texture, glossiness, transparency, and how light reflects on the surface are just some of the factors that can be affected by the glaze. On the other hand, glazing can also be quite unpredictable, particularly if you’re still getting to know what works and what doesn’t.
Knowing some basics about glazes makes the whole process much more purposeful. Rather than selecting a glaze just because you liked the color of a sample, you can start thinking about how it might work with your piece’s shape, texture, and clay body.
What Is a Glaze?
A glaze is a special coating that goes onto the clay and is transformed in the kiln. When heated, the glaze materials melt together and create a glassy surface on the ceramic.
The finish could be glossy, matte, satin, translucent, opaque, textured, or something in between.
Glazing does more than just add color. It can accentuate carved lines, smooth out textures, highlight raised shapes, or transform the overall appearance of the piece.
For that reason, glazing should be thought of as a design element, not just a decorative finishing touch.
Pick a Glaze for the Clay
First, make sure you choose a glaze that’s appropriate for the clay and firing temperature you’re working with.
Clay is made for certain firing ranges, and a glaze designed for one firing temperature might not work properly at another.
The compatibility of glaze and clay can also influence the finished glaze. The same glaze might look different, for example, depending on the color and composition of the clay body beneath.
It’s a good idea to research the recommended firing range for a glaze before applying it to a piece you care about, and test the combination when you can.
Don’t Judge by the Raw Look
Glazes often look entirely different before and after firing.
A powder, liquid, or unfired glaze might not reflect the actual color or surface that will appear after firing.
That can make glazing seem unpredictable at first.
To learn about a glaze, start by looking at fired samples. Eventually, you can develop your own reference library of how various glazes look on different clays, and at different thicknesses.
Clean the Surface
It’s important to start with a clean surface when applying a glaze.
Before you apply the glaze, make sure there isn’t any loose dust or debris on the ceramic. Dust can prevent the glaze from going on evenly.
The condition of the bisque-fired piece is also relevant. Minor flaws, rough spots, or lots of dust may stand out more once the glaze is added.
Give the whole piece a quick once-over before you begin.
You’ll find the glazing process much more manageable with a little prep work.
Spread It Evenly
The thickness of the glaze can have a big effect on the final outcome.
If the glaze is too thin, the surface may be lighter, patchier, or otherwise less developed than you expect. If it’s too thick, the glaze may run during the firing process or result in a different-looking surface. Don’t worry about getting a thick coat on when applying your glaze.
There are many different ways to apply glaze. Whether you brush, dip, pour, or spray the glaze can look different. It depends on the size of the item you are glazing and whether you are using a specific type of glaze.
Don’t forget about the edges
The edges of an object often get more glaze on them than the rest of the piece.
If glaze is pooling around a rim, a raised detail or where the surface changes from vertical to horizontal, there is likely too much glaze in that spot.
Having extra glaze in those areas can affect the way it looks and the way it fires. Check the edges of the piece and wipe away any excess glaze before putting the piece in the kiln.
Be sure the foot is clean
One of the biggest practical rules for glazing is to ensure that the foot of a piece doesn’t have glaze on it. If you leave glaze on the foot of a piece, it will melt in the kiln and stick to the kiln shelf.
Check the foot of the piece before putting it in the kiln and remove any excess glaze that could be sticking to the shelf. This is an easy mistake that can cause a lot of damage to your piece and to the kiln shelf!
Consider the shape
The glaze should fit the shape of a piece. A heavily textured surface might benefit from a glaze that plays up the texture. A simple, smooth vessel might be better suited to a finish that doesn’t distract from the form.
Think about how the light will bounce off the surface once it is finished. A gloss finish will emphasize the contours of the piece with light reflecting off it. A matte surface will give the piece a softer, less busy feel.
The same form can look very different depending on the glaze you use.
Think about color
A glaze can change the whole feeling of a piece.
Before you select your glaze, consider what you would like your piece to say. Lighter colors will make the piece feel softer, while darker ones will make details stand out.
You don’t need a huge selection of glaze colors to make a great body of work. Using a small palette can actually help unify your work.
As you start to use fewer glazes, you will learn more about how they react to the firing and each other.
Don’t be afraid to layer
There are many potters who like to layer multiple glazes.
Layering can make for interesting effects, especially if you know how the glazes interact with each other. However, if you don’t know how a layered glaze will turn out, the results can be unpredictable.
It’s always a good idea to do a few test tiles first before committing to glazing an important piece. Write down what order and how much of each glaze you used so you can recreate the effect.
This way you can treat it like an experiment instead of guessing.
Do some tests first
Doing some testing is one of the best things you can do as a potter.
A small test tile will show you how the glaze will react to your clay body, how thick or thin to apply it and how it will react to the firing temperature.
Try varying one thing at a time. You can see the difference between a thin, medium, and thick layer of the same glaze. The difference can be pretty drastic. Store successful tests and mark them with information such as the type of clay, name of the glaze, how it was applied and how they were fired.
Keep a Glaze Journal
A simple glaze journal can save a lot of time.
Record what you have used and how it was applied. Should the outcome be excellent, you will know how to do it again.
If things go wrong, the journal may help you figure out why.
Eventually, it will serve as a personal reference to document your experience.
Don’t Expect All Firing to Look the Same
Firing ceramics is affected by a variety of factors.
Kiln atmosphere, position in the kiln, temperature, the thickness of the glaze, clay body and firing schedule may all affect the appearance of a glazed piece.
So a pair of identical vessels made with the same glaze may not look identical.
While this is frustrating, it is simply the nature of ceramics. It is one of the reasons why ceramic works are unique.
Learn From Unforeseen Outcomes
It is sometimes the unintended glaze result that provides the most interesting discoveries.
The colour might turn out differently than you had planned, the overlay of multiple colours might create an unexpected surface, or a textured surface might reveal itself during the firing process.
Don’t dismiss the result immediately. Instead, consider why it has happened and whether it could be done again.
Doing so turns accidents into discoveries, helping you understand ceramics better.
Avoid Overdecorating
Glaze is a strong medium, and it is easy to use too much.
When a piece already contains interesting forms, lines, carved designs and textures, additional glaze application might end up competing for attention.
Sometimes, a simple glaze is sufficient to highlight the qualities of the clay body.
Before applying another layer or colour, ask yourself if it is really needed.
Good design is often determined by knowing when to stop.
Glazing as a Design Element
As you become more confident with glazing, it can become an integral part of designing a piece.
Instead of making a piece first and then glazing it, you can conceive the relationship between the form and the glaze beforehand.
A carved design may have been made with a specific glaze in mind, or the curves of a vase may have been conceived to allow light to play off its surface.
In this case, the form and the finish are integrated.
Summary
Glazing combines an understanding of materials with experimental creativity.
Begin with a clear understanding of how the clay body and the glazes interact with each other, prepare the surface properly, and apply it consistently. Test new combinations on small pieces, and keep a record of your discoveries.
Most importantly, allow yourself to experiment.
While a glaze might produce unexpected results, it doesn’t mean that you have failed. The more you learn through testing and observation, the easier it will be to decide what works.
Eventually, you will see glazing as a creative tool rather than a technical step.