Tactile Geology


I’m trained as a geologist, but I’ve been working with ceramics full time for 35 years. As in geology, I like the nature of materials and how they transform through heat and pressure. I choose to use a highly grogged terra-cotta clay for its structural strength, its gritty tactile quality, and its beautiful color when fired. I like the tactile quality of clay, so I sculpt by hand and I make up nearly all of my glazes from scratch.

I choose to live on the edge of the Atlantic where the weather is ever changing and raw, and I like that this same sort of ruggedness is in my work. A sense of place inspires me: the elemental world around me, the plants, the animals, and the myth and history behind us. This informs most of the imagery that I use. I rely on handbuilding techniques to make a form that echoes the images I am drawn to.

Bru na Boinne and detail.

St. Finians Bay and detail. Cormac Boydell works with raw minerals to make his glazes, showing evidence of his scientific former self, and to create an alchemy of bright colors and a dynamic and energetic surface on each piece. 


Slumping a Rugged Slab

Make a plate form much as you would make pastry for a pie: pressing out a block of clay on a piece of canvas (1), turning it over and rotating it regularly to even out stresses in the clay (2), and leaving the edges largely as they develop as they are an expression of the quality of the clay and the making process. Finally, lightly even out the thickness with a wooden pastry roller (3). I prefer the clay to be a bit chunky, so I leave mine quite thick.

To form the plate shape, transfer the slab to a plaster slump mold (4) and leave it to dry at room temperature just until it holds its form (soft leather hard). Then, fill it with crumpled newspaper to support the form (5), place a board on top, then turn it over.

Next, score and moisten the base where a foot and hanging lugs will be added. Roll out an even coil, then shape and attach a foot and two lugs with your fingers (6). Make holes in the foot and the lugs to attach wall hanging hardware after firing. I then inscribe a catalog number, the date, “not for food use,” and a signature into the clay. Now, turn the plate over onto a flat surface to level the base. Turn it over again (with the structural support of the newspaper) and leave until it’s bone dry.

1 Take a loose-formed lump of grogged terra cotta and press it out gently, making a nice outline.

2 Turn the clay over and rotate the slab regularly to even out the stresses in the clay as it thins out.

3 Even-out the clay’s thickness with a wooden rolling pin, rolling gently in different directions.

4 Peel the clay off the canvas and transfer it to a plaster slump mold. Set it aside to firm up.

5 When it has firmed up, fill the dish with crumpled newsprint, cover it with a rigid board for support, then turn it over.

6 Score areas for a foot and hanging lugs, soften the scores with water, then add a coil foot and lugs.


Bisque Firing

Large plates and platters (approximately 18 inches in diameter) are prone to warping during firing, so I fire them on edge (vertically). They’re also prone to dunting (cracking) if the temperature increase is too great over the quartz inversion points in the firing cycle. So I program my electric kiln with the following cycle:

150°F per hour to 212°F, with a 3 hour soak to make sure that clay is very dry

150°F per hour to 1050°F, soak 10 minutes to settle

15°F per hour through quartz inversion (@1065°F) to 1085°F

150°F per hour to 2030°F (cone 02), soak 60 minutes to settle and burn off any volatiles in the clay

cool down at 150°F per hour with slower rate programmed through the quartz inversion

Making and Cataloging

Although I like the uncertainty of the ceramic process, it’s essential to keep notes of every step, otherwise there is no hope of repeating or side-stepping any surprise result. Each glaze measurement is noted, together with the firing cycle, and on completion, is combined with a photographic record of the piece.


Glazes and Decoration

Often referring to one of my drawings on paper, I usually make a minimal drawing on the bisque-fired ceramic with a graphite pencil to establish a basic compositional framework for the design. Next, I lay down the design using a slip trailer and a semi-vitreous engobe (7). This works best when each mark is determined by the previous marks, so that the design is fluid and not made rigid through following a pre-determined path. When done, look quietly at the whole piece and ask: Is the design alive and rhythmic? If not, adjust by adding or scraping away (for safety, do this outside with your back to the wind, and wearing a dust mask). Then apply wax resist to the lines with a brush.

There can be a tendency for relatively low-frit glazes with added zirconium to crawl so I paint a higher frit sub-glaze layer over the lines (8).

Consider the colors and surface qualities and how they might work with one another within the context of the ceramic piece as a whole and create individual glazes for the piece with this in mind. Since I like a connection with the subtle characteristics of the minerals that I am familiar with from my geological experience, most of my glazes are based on a combination of frits and nepheline syenite, which I adjust the matteness as desired for each specific piece, and are opacified with either zircon (for a hard white) or tin (for a softer white).

As for colors, for pure yellows and oranges, I use potassium dichromate (which mimics the mineral crocoite), for soft ochre yellows I use vanadium pentoxide, for greens I use copper oxide (which mimics malachite), for blacks I use manganese dioxide sometimes with cobalt oxide added, for inky blues I use cobalt oxide (which mimics azurite), and for Egyptian blues I use copper oxide in a high-alkaline-based frit.

I add these into the spaces between the waxed lines using a laden watercolor brush or a slip trailer (9). In places, I lay on a heavy oxide layer, which will burn through subsequent over layers of glaze (10). Finally, since I usually finish the pieces with a rim of gold or platinum luster, which requires a glossy base, I add a glossy glaze to the rim.

7 Loose minimal drawing with graphite pencil as a basic compositional guide, then a drawing in glaze with a slip trailer.

8 As a crawling antidote, paint in a sublayer of glaze that’s more fluid than the final surface glaze.

9 With a slip trailer or brush, fill in areas with a pale yellow glaze. Then apply a wax resist over it.

10 Paint in oxide-rich layers. Note: the pink dye is a reminder of where to place additional glazes and wax resist.


Glaze Firing

I follow a similar (electric) firing cycle used for bisque firing when glaze firing, except I skip the drying section at the water boiling point, and the top temperature is lower than the bisque firing, usually to cone 06. Above this temperature, the chrome yellows tend toward browns. Note: I place the pieces horizontally in the kiln rather than vertically as I did in the bisque firing.

Edit Firings

Nothing is exactly as imagined in ceramics, so I look unhurriedly at each piece after the firing. Some turn out better than planned, but more often the pieces need editing (11).

As I usually want to preserve the results of the first glaze firing, I adjust additional glaze edits to mature at a lower temperature, typically reducing the top temperature by about 60°F in each subsequent firing.

Often I will add a textural layer in places. This can give a nice contrast to the semi-matte or glossy surfaces, and introduce a liveliness to the design.

11 Determine post-firing glaze edits then fire it again to a slightly lower temperature to prevent the original glazes from moving.

12 Loosely apply a gold luster edge and fire to cone 017–016. After firing, attach a hanging loop, photograph, and catalog.


Enamels and Lusters

As the clay that I use is rough and earthy, and the way that I work is hands-on and loose, I like to contrast this by adding a loose edging of precious metal (gold or platinum) (12). This edging also has a nice way of catching the light, and of making the colors more vibrant—similar to the effect of a gilt frame to an oil painting.

Cormac Boydell is a trained geologist who has been working for 35 years as a full-time artist working predominantly with clay. In ceramics he is self taught. He lives outside the small village of Allihies on the southwest coast of Ireland, www.cormacboydell.com.

Subscriber Extras: Archive Article and Images


Click here to read the archive article tip, “Hanging Systems That Help Functional Pottery Double as Wall Art,” by Annie Chrietzberg, which originally appeared in the July/August 2009 issue.



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