| From the pages of Pottery Making Illustrated
Photo Lithography Transfer on Clay by Kristina Bogdanov
Lisa Dorazewski’s Endangered Species, 4 inches in height each, porcelain Polaroids with photo transfer printed images, cone 6.
Kristina Bogdanov’s Positive & Negative, 12 inches in height, porcelain vessel with photo transfer printed images, cone 6.
| Clay is one of the most receptive materials and its ability to record even the delicate pattern of a fingerprint has been the biggest motivation in my work. Although I focused on sculpture and pottery as an undergraduate, I fell in love with printmaking while in graduate school. Wanting to combine two-dimensional media with my three-dimensional work, relief printing on clay seemed a natural starting point, since clay can pick up almost any texture. Moving forward, I began layering images, working with photo transfer techniques on clay work that would survive cone 6 firings. The resulting technique is closely related to traditional lithography.
Printer
Using a Xerox image, gum arabic and inks made from linseed oil and Mason stains, you can mimic the lithographic process on clay. When the image passes through a photocopier, a heat process burns the image onto the paper with a thin layer of plastic material, fixing the image to the paper, and making it nonporous. This nonporous area repels water, but attracts oil-based inks while the bare paper does not. (Note: Images from ink-jet printers won’t work for this process, since most of the inks in these printers do not repel water. If you don’t have a photocopier, try your local library or a copying service like Kinkos.)
Ink
The key to successful viscosity transfers depends on mixing the correct ceramic ink; the chemical make-up of the Mason stains you use determines whether the process will work or not. For example, when helping a student, the first ink we tested used Mason Stain 6650 black and the test failed. We tried this black ink several times, altering the photocopied image, testing very moist, fairly moist, leather-hard and bone-dry slabs, altering the ratio of Mason stain and linseed oil, but it simply didn’t work. Finally, at the point of complete disappointment, I decided to try a different stain, Royal Blue, and it turned out to be our “lucky accident.” The first run with this stain printed perfectly.
What happened? MS 6650 is a cobalt-free black, while MS 6339 Royal Blue contains cobalt. So far, all the stains that contain cobalt and chrome, including MS 6339 Royal Blue, MS 6537 Mouse Gray and MS 6109 Deep Brown, work with this printing process and the transferred image withstands both cone 6 and cone 10 firings. Metallic oxides, including manganese oxide or iron oxide, also make fine ink. If you want a wider color palette, mix small test batches of ceramic ink using the colors you want to try, and print with it on test tiles or slabs before using it on a finished piece.
Lithography Old & New
Lithography, which literally means “writing on stone,” makes use of the fact that grease and water do not mix. Invented as a lucky accident in 1798 by Alois Senefelder who wanted to switch from printing with expensive copper plates, the technique consists of drawing with a grease pen or other water-repellent material on a porous limestone block. The drawn on areas accept an oil-based ink while the bare stone does not.
Don Santos was the first ceramist to recognize that a photocopy behaves like a greased lithography stone. He developed this printing process, known as “viscosity transfer.”
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Process
Select an Image
Getting a crisp, perfect transferred image depends a lot upon the contrasts in the xeroxed image. Although gray tones will print, you get the most vibrant transfers from high contrast images. If you have a lot of gray tones that you don’t wish to compromise by adjusting the contrast, use Photoshop to modify the image so gray areas are created using half-tone dots. This creates the effect of middle tones using only black and white dots. Create a mirror image of the source, again using Photoshop to ensure that any text will read as it should, rather than backwards. Once the source is ready, photocopy it so the image will transfer properly.
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| 1. Coat a clean glass surface with a small amount of gum arabic. | 2. Spread enough gum arabic onto the glass to cover the back of the paper.
| 3. Place the photocopy on the glass. Spread gum arabic onto the image. | 4. Put several drops of ink onto the glass surface.
| 5. Use a brayer to spread the ink into a thick layer onto the glass.
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Mix the Ink
Mix a small quantity of ceramic ink using two parts dry stain to three parts linseed oil. Be sure to wear gloves and a respirator whenever working with dry materials. The consistency of the mixed ink should be like that of acrylic paint. If you’ve added too much oil, the ink will run off of the spatula too fast and as you roll it, the brayer will have an uneven, textured coat of ink.
TIP: Mix only enough ink that you can use within a week or two. Even if you store inks in sealed containers, they tend to dry out quickly, especially during the summer months. Once dried, ink cannot be used or fixed by adding more oil.
Prepare Your Image for Printing
Once you have the image ready, coat a clean glass surface with a bit of gum arabic (figure 1). Gently spread gum arabic with the palm of your hand (figure 2). Lay the Xerox copy over it, with the image side facing up. Run your palm over the image, spreading the rest of the gum arabic and making sure that the paper is adhered to the glass surface correctly (figure 3). The gum arabic on the surface will keep the ink from filling the white areas of the image.
Fill a medium-sized bowl with water and a splash of gum arabic. This is the solution used to wash out the excess ink that you roll on the Xerox image in the next step.
Spread the Ink
Using a spatula or scraper, scoop out some of your pre-mixed ink and trail several drops of it onto the glass surface (figure 4). Keep several inches between your image and mixing area clear of ink. Spread the ink out into an even layer on the glass by rolling the brayer through it as you would with a roller when applying paint to a wall (figure 5). Once the ink is spread out, roll the brayer over the inked-up glass a few times to evenly coat the roller surface.
TIP: Be careful that you don’t use too much gum arabic, as it will cause problems when you roll the ink onto the paper.
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6. Ink the image with the brayer using gentle and even pressure.
| 7. Squeeze some water and gum arabic solution onto the photocopy.
| 8. Clean ink from the white areas of the image and blot excess water.
| 9. Carefully lift the inked photocopy from the glass. | 10. Place the inked photocopy face down on a leather-hard slab or vessel.
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Apply Ink to the Image
Apply gentle pressure when inking the photocopied image (figure 6). You’ll notice almost immediately how the ink is sticking to the black of the photocopy as well as to the white of the paper. Dip a sponge into the bowl of water and gum arabic solution and squeeze it out over the photocopy (figure 7). Remove the excess water by blotting the image with a sponge. The solution will push the excess ink from the bare paper areas of the image towards the inked areas or onto the surrounding glass (figure 8). Then repeat the process three to four times. Apply ink again with the brayer, then clean off the excess using the water/gum arabic solution and sponge. Washing out will not remove the ink that adhered to the black of the photocopy, since water and oil don’t mix. These areas will build up a thin layer of ink each time you repeat the process, so your final print will have even, solid lines and blocks of color.
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Transfer the Image
The next step is to lift the inked paper and press it onto the clay surface. Lift the paper with great care, since it’s very moist and will rip easily (figure 9). The best printing qualities are obtained when you print on moist to leather-hard clay. Bone-dry clay does not absorb the image as well. If the clay is too soft, the combination of inked and wet paper on a moist surface will cause the image to smear. Once you’ve placed the paper on the clay surface (figure 10), press it down gently with a damp sponge so it adheres to the clay (figure 11). As the paper starts to dry, use the back of a plastic spoon to buff and further compress the image into the clay. When the paper is completely dry, it easily removes from the clay (figures 12 and 13).
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11. Press down gently on the back of the paper with a sponge.
| 12. Remove the paper when it is completely dry. | 13. Original photocopy and leather-hard vessel with photo-transferred image. |
TIP: Though prints are always monochromatic, you can print over underglazes or slips to increase the color range of the overall image.
Finishing
Once your pieces are dry, bisque fire them to the recommended temperature. Be careful not to touch the image, even after the bisque firing, since the stains can be smeared. Spray or dip the piece in glaze for the best results. The image becomes permanently fixed onto the surface only after the glaze or high-temperature firing.
The advantages of the photocopy lithography process are numerous. It’s a very cheap and easy way to transfer photographic images onto a variety of objects, from tiles to vessels to sculptures. The image is transferred after the paper is wet and flexible, which offers you the possibility to print not only on flat slab surfaces but on concave and convex surfaces as well. Since the inks are mixed from Mason stains and applied on greenware, it’s very integrated into the actual ceramic firing process, and the image is durable and permanent once the piece has been glaze fired. The process does not use solvents, and so is a nontoxic process that does not require special ventilation.
Kristina Bogdanov teaches ceramics at Ohio Wesleyan University in Delaware, Ohio. She acknowledges the research of Don Santos, as well as help from University of Kentucky faculty and staff including Professor Ross Zirkle, Tamarind Master Printer, printmaker Gerald Ferstman and Professor Bobby Scroggins, ceramist; and her current students at OW, including Lisa Dorazewski in the development of this process.
| Tools
All of the supplies you will need to do this process can be found online or at art stores, many can be found at craft and hobby stores too. The tools you’ll need include:
Brayer–a hand roller used to spread the ink out into a thin layer on the glass and apply it to your image.
Photocopied image with high contrast or an im-age altered in Photoshop using half-tone dots to create gray areas.
Spatula, scraper or putty knife for mixing the ink and applying it to the glass
Mason stains or metallic oxides containing cobalt or chrome for use as colorants.
Gum Arabic to hold paper in place and to remove excess ink from white areas of the photocopy.
Linseed Oil for mixing ceramic ink.
Small sponge for wetting paper and cleaning off excess ink.
Medium sized metal bowl for water/ gum arabic solution.
12×14 or larger piece of tempered glass or similar glass surface for mixing and spreading the ink.
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