September 5, 2003, Newsletter Issue #155: Glaze Techniques

Tip of the Week

Tips for glazing beautiful pots

As we become better at making beautiful forms we don’t
necessarily become better at achieving great glaze results.
It seems so unfair! If you are serious about achieving great results your first step is to begin your own glaze journal today.

It’s important to do many different things right before you
can be successful at glazing.

First, consider what textures and colors you want the
glaze to contribute to your finished form.

Many art centers and community labs have test tiles you
can observe before you commit to glazing with them. (If
you are at a home studio, you will want to create your own
test tile pattern with some of your favorite glazes.) We
recommend you test one coat or two to see if it runs or
changes colors when applied thicker. Also, test glazes on
different clay bodies.

If your facility has tiles, they probably indicate which glazes are stable and which glazes run. Glazes that run are not suitable for the outside of a piece. A glaze that runs can run off the pot and onto the kiln shelf making a huge mess.

The same glaze can look very different on various clay
bodies. Also, it may look different when applied thin vs.
thick. An example is a copper red glaze called Oxblood, it´s white when applied thin, red when applied thick - quite a difference.

The next step is choosing a suitable glaze for your clay
body.

Earthenware Glazes (low fired - Cone 04- 06)
Earthenware glazes are more straight forward and
predictable than stoneware glazes, they are mainly shiny
and come in only a few colors. Usually clear, white, blue,
and amber are available at most art centers or community
studios. The best way to apply earthenware glazes is to
brush it on your pot.

You can have fun applying slips to earthenware clay for
designs or variations. Bright colors can be produced by
applying mason stains. Flower pots are unglazed fired
earthenware.

Stoneware Glazes (high fired - Cone 4-10)
Stoneware glazes offer a much more diverse range of
colors and textures. They are usually applied by dipping or
pouring the glaze over the piece. There are a few glazes
with ‘universal’ appeal. They are known because of their
consistent and predictable results. Following is a brief
description and review of different stoneware glazes.

Celedons- for example Hot Tea with Iron, or Celedon
Leach Korean are well know recipes. Celedons are
stoneware glazes that contain iron which produce green,
gray and gray-blue colors in a reduction firing. Usually with many visible small cracks.

Copper reds- for example Coleman’s Copper #2, or
Oxblood are well known recipes. Copper reds are
stoneware glazes that go from white to bright red in a
reduction firing.

Shinos- for example shino can vary from white to orange in
color. Shinos are stoneware glazes which when applied
thin will be white and when applied thicker will be orange.

Temmekous- for example temmekou is a stoneware glaze
which can vary from a beautiful black to a rich brown.

Last, let´s consider the pros and cons of high fired
glazes versus low fired glazes.

Pottery fired to Cone 10 or higher is generally safe for food. As long as the clay has been fired to Cone 10 and vitrified, it should be safe from bacteria. Low fired pots can potentially capture bacteria in cracks in the glaze or clay body since it´s not vitrified. So, if you are making functional or utilitarian pottery to be used with food, you need to use a high fired clay body and glaze.

Some potters prefer stoneware glazes because the
variations are so diverse. You could spend a lifetime
experimenting with some glazes. You don’t have to know
chemistry to be a fine potter, but to really progress with
glazing you need to learn as much as you can.

Begin looking at glaze recipes in terms of the role of each
ingredient. Notice which oxides are in the glazes you are
using. You quickly learn patterns. Each compound has a
job to do in a glaze. Learn about the chemicals and you
can begin to control the results.

Happy Glazing!

About LifeTips

Now one of the top on-line publishers in the world, LifeTips offers tips to millions of monthly visitors. Our mission mission is to make your life smarter, better, faster and wiser. Expert writers earn dough for what they know. And exclusive sponsors in each niche topic help us make-it-all happen.