Ceramic surfaces have captured my interest from the very beginning of my clay journey. The merging of imagery and form is a limitless exploration of ceramic materials. Layering slips, techniques, and glazes can add depth, movement, color, and illustration to clay vessels. I am intrigued by the marvel of how these combined natural ingredients will emerge from the heat of the fire joined into a single body.
Throwing a Bowl
Begin by throwing a bowl form with approximately 1½ pounds of clay. Center and open the clay leaving ½ inch at the base to allow for trimming a foot later. Throw an open bowl form, keeping your walls around ¼ inch thick with a bulkier rim. Next, use a rib to create a smooth continuous curve on the inside of the bowl (1). Don’t worry about refining the outside of your bowl during this part of the process.
Timing and clay moisture are very important for the success of altering your form. While your freshly thrown bowl is setting up, roll out a slab, leaving both wrapped together under plastic overnight. When the clay is at a medium leather-hard stage, trim a foot on your bowl and refine the outside shape following the curve on the inside (2).
Altering the Form
Continuing with your clay at the medium leather-hard stage, begin the alterations by slicing off a section of the rim at a 45º angle using a sharp knife blade (3). Repeat on the opposite side of the bowl and place the removed slices on the slab to use as templates in creating the new rim pieces.
With a water-based marker, trace the edge of the sliced rim and draw the shape you wish to cut out (4). Consider the profile of your bowl and how it will relate to the surface you are planning. Your new section of rim can be playful, whimsical, and have straight lines or curves.
Cutting with a needle tool rather than a blade can be helpful in preventing cracking on shapes with an acute inner angle such as scallops. Cut out the form using a 45º angle on the bottom edge where it will attach to the bowl (5). You may need to make additional adjustments to the bottom edge of the attachment to match the curve of the cut edge of your bowl. Soften the rim of the attachment by placing it between two pieces of paper, then rub your finger over the edge on both sides (6). Score and slip to attach the new rim pieces to the bowl (7). Compress and smooth the outside edge of the attachments with a rib (8). Use a coil to reinforce the inner angle of the attachment.
Place the bowl under plastic until the form is at the hard, leather-hard stage (like Parmesan cheese). Once at this stage, it will be ready to decorate.
I use a paper-resist technique to create a floral design on the surface of my vessels. Newsprint or standard printer paper work well for this process. Fold your paper or use multiple pieces to cut out several layers at a time. Sketch your design on the paper, then cut it out with scissors (9). Plan the composition of your design by holding up the paper pieces and loosely drawing the shapes with the water-based marker directly onto the surface of the leather-hard clay (10).
The first layer of decoration is created with underglazes. These can be commercial underglazes or engobes you have mixed yourself. The idea is to create an interesting and varied surface at this stage, as well as establish the main color palette for your surface.
Decide on the color palette, then take those colors and create a couple of different shades of each. For example, if you are planning to have purple, orange, and pink flowers, use two different purples, light and dark orange, and so on. Working with multiple shades will give you a complex, painterly look.
Next, brush on underglaze colors then quickly run a silicone combing tool through to create visual movement and texture (11). Alternatives to combing could be sponging, stamping, or dappling. Allow the underglaze to dry to the touch before moving on to the next step.
Layers of Slip and Paper Resist
While waiting for the underglaze to set up, prepare materials for the next layer of decoration. You will need a freshly sieved white slip that is the consistency of heavy cream and a paintbrush. The paintbrush that you use will determine the texture of the brush marks. An old chip brush makes unmistakable brush strokes, while a mop brush will create a smoother look.
Apply the pieces of paper you have prepared to the surface of the clay by patting them in place with a damp sponge, taking care to make sure all the edges are securely attached (12).
Now, brush white slip over the entire piece covering the paper, using deliberate brush strokes as these will add depth and texture to your overall design (13). Generally, three coats of white slip are enough to create contrast for your paper-resist design, while remaining semi-transparent after glazing. More white slip layers will add more opacity, while less will be more transparent.
After the slip layers have dried enough to handle, use the sharp tip of a blade to lift the paper pieces off (14).
Sgraffito and Slip Trailing
Dimension and tactile texture can be added to your design with sgraffito and slip trailing. The slip layers introduce a lot of moisture back into the clay, so wait until it has returned to a hard leather-hard firmness before carving sgraffito details. I choose to follow the shape of my flower cutout, carving lines through the white slipped layers (15).
Use a smooth slip that is the consistency of yogurt for trailing. You can test the slip by squeezing a bit from your slip-trailing bulb onto your hand. It is just right when it does not form a stiff, sharp peek, nor does it drip. Outline the flowers with slip in the colorful areas of the cutout, stopping at the points to break up the consistency of the line (16). After trailing slip details to your surface design, leave the bowl to completely dry, then bisque fire.
Rinse the bisque-fired bowl under water and examine it for sharp spots or flaws. Lightly wet sand any sharp edges (17). Allow the bisque ware to dry before applying a clear glaze of your choice (18). The white slip will look completely opaque at the bisque stage; however, it will become semi-transparent with a coat of clear glaze in your final firing. Fire in an electric kiln to the appropriate temperatures for your clay and glaze.
Choosing a Clay Body and Glaze
This layering technique works with any type of clay body and firing range with an array of results. Consider these things as you experiment: a dark clay will create a lot of visual depth in your surface layers, while a white clay will have flatter but brighter colors. Use a white slip that fires to the same or higher cone as your clay body. For example, if using a cone-6 clay body, make sure your slip also fires to cone-6 or higher. Use a clear glaze that fits your clay body as well. For added variety, try a satin clear glaze or a celadon.
Amy Irish makes functional and decorative work out of her home studio in Hillsborough, North Carolina. She’s inspired by the little things in the world around her. Her children, the garden, and preparing food for her family are all sources of joy that she hopes to share and connect with you through clay. You can find her on Instagram at @amyjirish or on Etsy at www.amyirish.etsy.com.