Beyond the Rainbow: The Colorful World of Commercial Underglazes

“Teapots” by Jim Kemp. Jim uses a low-fire red clay body and airbrushes underglazes onto the greenware. The last color he applies is black, which is sprayed across the piece to highlight the variations in heights of the surface decoration. The pieces are once-fired to cone 02.

Over the past several years, underglazes have become my absolute favorite decorating tool. The sky is the limit when it comes to the ways underglazes can be used.

In today’s post, David Gamble explains how a number of artists use underglazes in their work. It should provide plenty of inspiration if you have been thinking about exploring the world of underglazes! – Jennifer Poellot Harnetty, editor.

Chicago, Illinois, artist Scott Rench silk screens images he creates on his computer. Images are screened onto the clay while it is still wet so it can still be shaped. After bisque firing to cone 04, Scott airbrushes a clear glaze and fires again to cone 04.

Commercial underglazes are basically clay slips containing colorants, and they’re a great way to add color to your work using a variety of application methods. And since they’re formulated to have low drying shrinkage, they can be applied to bone-dry greenware or to bisque-fired surfaces. In addition to being able to change the surface color of your clay body, underglazes can also be used to change the texture of the body.

When used to add color to surfaces, underglazes have an advantage in that they are composed mostly of clay with very little flux, so they’ll stay put and won’t run, which makes them ideal for detailed decoration. While most underglazes were originally formulated for use at low-fire temperatures, most, maintain their color in the mid range and some even as high as cone 9 or 10.

Simple Application

Underglazes can be applied by brushing, pouring, dipping, spraying, sponging-pretty much anything goes. Each application method has different requirements. If an underglaze is too thick for spraying or using as a wash, just add water to thin it down. If it’s too thin for silk screening or monoprinting, leave the container exposed to air to evaporate some of the liquid.

Steve Howell of Gainesville, Florida, uses a body made from half porcelain and half raku clay. After the initial bisque firing, he adds underglazes and bisque fires again. After the bisque, he places the piece upside down in a 2×4-foot brick pit in sawdust layered with copper carbonate, salt and bits of sticks and wood, then covered with a Kaowool blanket.

Underglazes work best with a clear overglaze, although other glazes of varying opacity and color may also be used. I’ve had success with whites and very light-colored glazes, but darker glazes seem to muddy or absorb the color of the underglaze. The overglaze can be anywhere from matt to glossy. You’ll find the clear deepens the value of the colors regardless of application method. If you’re sealing the surface of work that will come in contact with food, be sure to use the appropriate food-safe clear that matches your clay body and firing range.

Applying an overglaze can be tricky. If you’ve applied underglazes on bisque, you’ll find that they’ll smear when brushing on a clear overglaze because moist glaze moistens the underglaze. Use a fan brush and float the first coat on without going over the same area twice. Wait for the first coat to dry completely before brushing on a second coat.

I’ve recently used underglazes to create a watercolor effect by thinning them down and painting them onto a semi-white glaze that is layered over another colored glaze underneath. The colored glaze (sometimes gloss, sometimes matt) melts through the white and gives it a richer off-white look. The clay body is a red terra cotta that can handle a number of multiple firings if needed. I’ve been creating pieces from my travel sketches to permanently document places I’ve traveled to in a sketchbook-like manner.

Platter by Rimas VisGirda

Rimas VisGirda slab builds his plate forms from a terra cotta body. Following a pencil outline, he brushes on underglazes then applies wax to the entire surface. He redraws the figure and the outer border by scratching through the wax and into the clay surface and then inlays liquid black underglaze into the scratched lines. After bisque firing to cone 05, he waxes the figure portion and outer edge again but leaves the background alone. After sketching in flowers with a pencil, he applies underglazes to the flowers, leaves and stems and further defines them with black underglaze. He applies wax over the flower stems and leaves then sponges blue underglaze onto the background. After firing to cone 5, he adds shading with an underglaze pencil then fire to cone 3.


 Erin Furimsky does amazing things with underglazes! In her DVD, Layered Surfaces, Erin shows you how to combine combine various techniques in creative ways to add visual depth in your surfaces. After you watch her demonstrate, you’ll be amazed at how you’ll be able to take a design of your choice and use it to create rich, intriguing, layered surfaces.

Read more and view a clip…

 In this example from my “Sketch Book Travels,” series, I bisque fired a clay slab to cone 03 then layered base glazes-3 coats of key lime with white, and 3 coats of low-fire white on top. The sketch is then executed with thinned out underglaze washes and fired to cone 04.Paul Wandless paints underglazes on plaster in reverse, painting the foreground first and the background last. He then pours a low-fire white slip on the plaster. This picks up the underglaze image and inlays it into the clay. After bisque firing to cone 02, he applies a thin clear glaze then glaze fires to cone 04.Tom Meunick uses white stoneware or porcelain then bisque fires to cone 06. He then uses underglaze pencils to draw on the surface. After drawing, he atomizes it lightly with water then applies a glaze by dipping or spraying.Ron Korczyski bisque fires a white low-fire clay to cone 04 then applies underglaze by brush on the bisque piece. He uses many underglaze colors in different size applicators that he can squirt out and draw line details and dots of color. The final piece is fired to cone 05.

  • Meryl S.

    Enjoyed reading this article and comments. I have a question! I have under glazed my Vase and waxed the bottom which I have now been told was not necessary to wax if using a Bisque slab larger than the vase that has already been bisque fired for the vase to stand on. I will fan brush the vase with clear glaze and was concerned that as I have already waxed the bottom there might be a problem. Can anyone let me know! Thanks. Meryl.

  • Bonnie B.

    Can you tell me if low-fire bisque dinnerware (painted with underglaze and clear glazed then fired to ^06) can be used in the microwave? Put in a dishwasher? Assume there is no luster or metalics used. If the bottom of the plate is unglazed, how does that affect washability? What do you do to inform your customer of the functionality?

  • john w.

    Underglazes don’t melt and stick to other objects in the kiln like glazes do, so you can apply underglaze to the bottom of your pieces without worry…or leave untouched – whichever you prefer.

  • Jean B.

    Linda, its imperative that you dont have glaze under your work. You can choose to use underglaze or leave the base virgin. The wax is applied under the pot to prevent the glaze sticking when you dip your pot. Droplets of glaze must be carefully wiped off or they will fuse to the kiln shelf. The wax just burns away in the firing and does not affect the work.

  • Linda E.

    I’m a newby and have a simple question. When using underglaze on unbisqued pieces, how do I treat the bottom?
    glaze?, wax? leave virgin? Thank you, Linda

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