Overglaze Technique

For more than twenty years, I have been using overglaze as a direct painting technique. My canvas usually is a fired, flux and white base coated enameled copper piece. Although I sometimes make a rough sketch for placement, I more often paint directly in an impressionistic style. Each painting is a new and different delight.

Even after all these years, the firing process is still able to produce a surprise often enough to hold my interest when I watch the enamel change color as it cools. When the result is not acceptable or what I intended, I enjoy working my way out of a color or design error.

I make wall pieces, plates, bowls, mezuzahs, and switch plates. The switch plates and the mezuzahs are small enamels that I use to experiment with new color combinations or a new design. In my studio, my work has ranged from 11/4″ cloisonn? jewelry to sectional pieces comprised of 12 " square segments. I use ceramic overglazes and china paints (on glaze enamels) and also mix them together to make additional colors. My overglazes are old ones, probably leaded, from Thompson Enamel and Standard Ceramic Supply Co. The china paints are from various china supply houses. Most china painters and enamelists mix the material with oils, but I use water to prepare the overglazes for painting.

In the early 1970s, I produced a series of enamels made with fine line black pen drawings and overglaze colors added with small brushes. While traveling in Canada I visited an enamel studio that had been marketing a line with the same technique. They, too, were painting flowers with the fine line black first. Shortly after that visit, I thought of using watercolor brushes first to paint the flowers and then adding the black pen line. The only overglazes I had were the limited colors that Thompson Enamel then carried. I stopped using this technique because I did not like the yellows and oranges when fired at 1500 F, and I thought the Thompson palette was inadequate. About a year later, while exhibiting at the American Craft Council Northeast Fair, I was browsing through the catalog of Standard Ceramic Supply Corp. and spotted columns of ceramic overglazes with enticing names from cream to dark purple. They fired at just under 1500 F, which was what I wanted. The sales representative told me they would not work on enamels and I would be wasting my money. I decided to try them anyway, despite his protests, and bought about 12 colors: yellows, oranges, pinks, purples and a deep blue. Most of them worked, and I am still using the Standard Ceramic Supply product. The ones I list below are my favorites. It was not until the late 1980s that I added the china paints.

If you want to add overglazes to your supply of enamels, buy the smallest quantity of about 8 10 colors to start, or a sample kit if it is available. A teaspoon amount lasts a long time. The china paints come in a glass vial. The violets and pinks are the most expensive. I am assuming that you know how to paint in some other medium. If not, you can use them to add an accent of color or shading to an area of fired enamel on your piece made with one of the beginner's techniques.

The Standard Ceramic overglaze colors I use most arc: Lemon ST114, Pink 236, Green 112 P, Canary 650/291, Dark Violet 324 and Orange 286. I use the Thompson 900 series, except the yellow and orange. Originally, I made color samples on 3 " x 8 " 20 ga copper that had a medium firing white base coat and black crackle on the back. My enamels are mostly 80 mesh leaded ones from Thompson that I purchased in quantity years ago. For the base coats I usually use Thompson's leaded 80 mesh #1005 medium flux, #1000 medium white, counter enamel, #124A hard black, #772 liquid form enamel and #426 soft flux over my name on the back.

I primarily use the #169 Norman kiln on a 220V line. The inside chamber is 16″ x 16 " x 9 ". The door opens horizontally from the right side. The pyrometer is set in the right rear corner. It has two variable control switches although I would prefer one switch. It was re bricked and rewired about 15 years ago. I have a reserve set of wires.

To prepare the overglazes for painting, I put about 1/2 teaspoon of each color in the bottom part of a 3 " plastic Petri dish near one side. The cover is labeled. I add water gradually with a syringe as I blend the overglaze to a painting consistency with a small bent painter's palette knife. My favorite knife has a 1/2 " wide straight edge because I accidentally broke off the tip years ago. I use tap water. When I paint, I tilt the uncovered Petri dish slightly so the overglaze is at the top of the dish and a little water at the bottom of the dish.

I work in a modified production style for the base coats on purchased 18 ga copper forms. If I am making 6 " to 8 " plates, I usually prepare about 12 pieces at a time for the paintings, which then arc painted in a number of sessions. If the base coat is to be a white or light opaque, I clean the copper pieces with Penny Brite. If the base coat is to be a transparent, I clean the copper on the polishing wheel with a goblet buff that has been charged with Lea Compound C. When clean, each piece is placed back side up on a 2 " bottle to be coated with black crackle, as shown on page 45. I brush on the crackle, let it dry and then sgraffito my name in the center with a sharpened chopstick. The loosened dry crackle is tapped off, and any dry crackle on the edge of the piece is removed with an edge of the square handle of the chopstick. The pieces arc placed face side down on a tray and transferred to the enamel worktable. I heat the kiln to 1500 F, and keep it there while I apply the enamel to two plate fronts. Before applying the enamel, I set up the kiln furniture to receive two pieces for firing. On each of two 6 " square nichrome mesh planches I place a 3 pointed stilt for firing the piece with the front side up. While a piece fires, I apply the enamel on the next one, keeping a production line moving. This part is just work. By firing a number of pieces, one after the other, the firing hardware stays hot and prevents a big drop in the kiln temperature when the kiln door is opened.

For My usual white base coat on the front, I mix about 2 pounds of Thompson's leaded 80 mesh, #1000 white and I pound of their #1005 medium fusing flux in a 5 pound jar. I like the softer look with a little of the flux showing through instead of a bathtub white porcelain look. To sift enamel on a piece, I use the 60 mesh, 2 " old fashion metal tea strainers that have sloping straight sides with the mesh flat across the bottom. Some of my sifters are labeled flux, white or counter. I only use them for what they are marked so I do not have to think about cleaning them. (See section on siffing base coats.) On the front, I sift a heavy coat of the flux/white mixture and a second light coat of white. The piece is sprayed with water before and after each sifting. With a light spraying of water, just enough to hold the enamel, I do not have to wait for the piece to dry. The first piece is placed on the set up stilt, put in the kiln and fired to maturity to ensure that the black crackle on the back is shiny and fired enough to adhere. While that piece fires, the next flux and white layers are sifted on the front of the next piece. The next piece is set on the other firing set up, the first piece is removed from the kiln, and the next piece is put in the kiln. The program continues until all the pieces have a fired base coat on the front and on the back. This is the base coat method of firing both enameled sides in the first firing that I learned from Doris Hall in 1955.

My counter enamel, with the 60 mesh sifter, for the second coat on the back is 2/3 left over 80 mesh enamels and 1/3 Thompson's 80 mesh, leaded, 124A hard black. By having the hard black in the mixture, I do not have to re enamel the back again. Soft flux, Thompson's #426, is sifted over my name. I sift 2 coats of counter on the back except over my name. As usual, a light spray of water is applied before and after each sifting. The same production line system is used, but with hammocks to support the plates with the back side up in the kiln. Each piece is fired to maturity. When removed from the kiln, the plate is transferred to a steel plate, back side up and weighted with an old iron until it cools. After all the pieces arc fired, and loose

firescale on the edges removed, the plates are ready to be painted. Each piece takes about seven firings.

I have a separate table for painting. The Petri dishes, with the covers on them, are set up as a color palette. Any overglazes that have dried out have a few drops of water added and arc blended smooth to prepare for painting. Two bottles containing water are also on the table, one for cleaning the brushes and the other for clean water ' along with a folded paper towel for wiping a brush and the syringe and water spray bottle. I use sable or kolinsky watercolor brushes. As with any painting medium, you need to practice the brush strokes and develop your own style and preferences for colors. For painting leaves, I use Lebenzon's custom made, kolinsky, broad, long pointed watercolor brush in the Chinese painting method. The brush is held vertically, pressing down on the heel of the brush for a broad stroke and gradually, as the brush is moved forward, pulled up off the paper for a pointed tip to the leaf. You need to remember that most china paints have lead in them and some have cadmium so do not put the brush in your mouth.

The overglazes handle like watercolor paints in that one wet color placed on another one will blend or bleed; but unlike painting on paper, the enameled surface does not absorb the overglaze. If part of the painting dries before you are ready to fire the piece, then the whole piece will need to be sprayed lightly with water. If the painting dries in sections, a line often appears between these sections when the piece is fired. The overglaze painting is dry by the time it is placed on the warm firing set up and put in the kiln. Plates and bowls arc placed in the kiln on a three pointed stilt on the planche; plaques are fired within a hammock. I fire with my kiln at about 1500 F. It is years since I tested the pyrometer reading. I really judge the heat by the color in the kiln and fire for time by instinct and a quick peek. Overfired overglazes will lose the intensity of their colors.

For my floral painting, I often start by painting various shades of green leaves with the kolinsky watercolor brush. Next come my imaginary flowers. The first flower is often the predominating color from which the painting develops. If I do not like a part of the painting that has dried, I remove it with a small, stiff, stencil brush. If the whole composition is not to my liking, the piece is rinsed off under running water. When the painting is at the point that it cannot be developed further, it is fired to just before maturity. Then if there are areas, say on the fired green leaves, where I want to add another flower, I either sift leaded, 80 mesh, #644, soft white in a shape and size or I wet pack an opaque over a leaf. To add color to this unfired white flower, I charge a brush with color and run the tip around the outline of the shape I want. A color can also be added within the added shape. The wetter the overglaze and the enamel, the more the overglaze color will bleed into the opaque white enamel. Instead of using the stiff stencil brush to remove part of the painting, you can use a wet clean brush.

Instead of mixing a color on your palette you can blend colors on the painted section when it is wet by charging the brush with thin overglaze and letting it run either where you direct it or by tilting the piece. Most of the overglazes arc transparent, but adding the white will tighten the color and also lose most of the transparency. As you work with the overglazes you learn which ones need to be applied thicker, like the reds that burn out faster than other colors.

When I consider the painting completed, I often delineate some of the shapes by drawing with Hunt's #101 nib in a pen holder (you can also use a ruling pen) and Thompson's fine line black, which I purchase in liquid form. (Some enamelists use it to sign their name on the front of their work ) I call it "Ink". I order it in the I ounce bottle because it takes a lot of stirring to put the glob at the bottom into solution. I use a dental spatula to stir the ink well, and separate it into four little glass bottles with screw on lids. Before using the ink, it needs to be stirred well again. I first test if it flows from the nib like ink and test if I can draw some lines on smooth paper. I hold the pen almost straight up when I write with it. If the ink is too thick, add artist turpentine one drop at a time and stir after each drop. You will need to stir the solution about every ten minutes as you use it and also dip the pen in turpentine from time to time for the ink sometimes dries on the nib tip. After you dip the pen in turp you need to re dip the nib into the fine line black a few times before you draw with it or the ink will be too thin. If you get an unwanted blob, wait until it dries and then remove it or part of it with a pointed chopstick. When the pen drawing is complete and dry, the fine line black is corrected with the chopstick. Then fire just until the drawing is smooth. You can test it, out of the kiln, with the edge of the potter's spatula. The wide areas will have break lines in them. I like that. If you overfire, the drawn line becomes thinner arid, of course, the overglaze colors are changed. I finish each piece with a sifted overall veil of 80 mesh soft flux.

The final step is to smooth the exposed metal edge. My sanding and polishing wheels arc connected to a dust collector purchased and installed by a local dental supply company. Even so, I don a nose mask, a facemask, leather gloves, and a shower cap over my hair before using the equipment.

The face edge of the piece is finished first at the belt sander with a 6 " x 48 " fine grit emery cloth belt. After grinding the front and back edge of each piece, I remove the grinding marks. I tear a sheet of fine emery cloth into 1 " x 12 " strips and wrap one strip around one end of a I" wide wood stick. Wearing leather gloves, I rub with the strip of emery cloth across the grinding marks to obliterate them. As the beginning wrap of the emery cloth strip wears out, I wind it a little to have a clean area to work with. The final finish is a rubbing of the metal with a wad of 00 steel wool. I place felt tabs on the back of the piece over the three stilt marks and then add my label. Each piece is placed in a plastic bag to keep it clean.

Another use I have found for the overglazes is to make pale opaque enamel colors when I need to match a client's color swatch. For a small amount of enamel, about an ounce of 80 mesh, maybe white, is put into a 4 ounce glass jar with about 2 ounces of water and 1/4 teaspoon of overglaze color in painting consistency This mixture is then well stirred and allowed to sit for about 15 minutes and stirred again. If you want it darker, gradually add more overglaze, stir and let it settle in. Pour off the excess water. Place the open jar with a loose piece of paper on top of it on top of the kiln to dry out. When the enamel is dry, you can wet pack or sift as you wish. If I am aiming for a specific match to a swatch, I often have to make a few different batches and fire samples on scrap copper.

If you like to paint, you will find the nuances of color that can be obtained with overglazes are limitless. The tactile quality of enamels as well as the sense of their enduring quality will bring you delight.