When I was first learning about pottery one of the things that confused me the most was “what was the difference between glazes and underglazes”. Most teachers focused on teaching you wheel throwing or hand building but very few actually teach you about glazing. At least that was my experience. Maybe yours in different…. I hope so… but if not here is a brief introduction to glazes vs underglazes.
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Glazes, overglazes and underglaze are all materials that can be used to decorate your pots, but they serve a different purpose.
What is a glaze
A glaze is a blend of materials that, when applied to a bisque pot and fired to a particular temperature, will melt and create a glass surface. The melting temperature is determined by the blend and ratios of the materials used to create the glaze. Once in the kiln, the materials in the glaze undergo transformations, fuse onto the pot and eventually the glaze becomes glass.
Glazes can create a smooth, matte, glossy and even a textured surface and can be either opaque or transparent. They also provide a protective layer.
Glazes can be applied over or under each other and how they react to each other determines the final look.
Some glazes are reactive meaning that they may run, change colors and, for the most part, can be rather unpredictable.
Some glazes are very stable and predicable.
Three different reactive glazes were used in the final decoration of this yarn bowl. I never know exactly how a piece will turn out so its always a surprise. I used a big floppy brush and applied each of the glazes in blobs overlapping at times. Not only did the glazes react to each other but also to the magnesium in the clay.
I am learning all about the chemistry of glazes and all the ins and outs of the materials used in making them but that is for another time!
If you buy commercial glazes the jar should tell you what temperature range it should be fired at.
No one will be able to tell you how a glaze will look on your clay body or how it will react to other glazes. Thats all about experimenting and experience that comes with it.
What is Underglaze:
Underglazes are what you use to color and decorate your pots when you need more control over the colors.
They can be applied to leather-hard, greenware or bisque pots.
Most of the time a transparent or clear glaze is applied over the underglaze to seal in the color and protect it.
Underglazes usually consist of colored pigments mixed with a binder, such as clay or gum. They are applied to the surface of the unfired pot by painting and you can create some pretty intricate designs.
Although underglazes can be applied to bisqueware, often times the decoration will bleed when the clear is applied so I suggest either painting on greenware and bisque firing the underglaze in and then clear glazing or paint on bisque, and rebisque. This will keep the decoration clean!
I love decorating my pots with underglazes/ There are many manufacturers and you can even make them yourself, but I have found that using commercial ones give the best results and are pretty consistent. My preferred underglaze is Amaco Velvets.
These are a sampling of my underglaze test tiles. The top of each tile has been left unglazed and the bottom has been clear glazed.
I share some of my techniques and favorite colors here.
Greens can be troublesome. I have found blending Intense Yellow (V391) with blues gives me prettier greens!
This set was painted in the greenware state. I used an airbrush for the green background.
This set is a combination of Sgraffito and underglaze. The sgraffito was done on Leather hard clay and the underglaze was painted when the piece was completely dry (greenware). I prefer to paint on greenware. You can paint on leatherhard but I find that the moisture in the clay can dilute and muddy the colors.
As you can see you can layer underglazes while you are painting. They blend into each other a bit when fired!
My name is Dani and I am the potter behind this page! I am retired and having a ball being the artist I always wanted to be. My studio is located in NW Arkansas where I live a quiet life, on a lake with my husband, 3 dogs and two cats.
Have a look around!
Amaco Velvet Jet Black Underglaze
Amaco Velvet Jet Black Underglaze is my base color for Sgraffito Work. I apply 3 coats on a Hard Leather hard piece to give a lovely opaque palette to work with. When Bisque Fired it turns a deep matte dark grey. Applying clear glaze brings out the shine and makes it very black.
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Amaco Velvet Underglazes
I have tried several different brands of underglazes but I keep coming back to the Amaco Velvets. They may be a tad more expensive but they are worth it
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Shimpo Banding Wheel
These may be expensive but they are worth every penny!! They are banding wheels on steroids! Super heavy duty and spins freely, smoothly, and quickly!!
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Miniature Paint Brush Set
For fine line painting,detail work or blending of my underglaze paint, I have found these paintbrushes to be perfect. They hold their shape and come in various sizes and shapes. You get 12 of them!
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Expanding my knowledge on making my own Pottery Glaze
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First show of the year selling my pottery
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