All of us have come into contact with decals — we see the commercial type every day on mugs, plates and other industrial ceramics. Getting these types of images on to a ceramic work is not necessarily that hard. In this feature I would like to have a brief look at some of the issues involved. Those wanting to actually get out there and do their own printing, I would like to refer to some of the technical literature on the subject available in may good technical ceramic books and magazines. You can also check out this really neat article by Rimas VisGirda, who explains his easy decal making process.
When making decals, ceramic oxides are mixed with a medium into a smooth paste, which is printed onto a transfer paper (usually a gelatin coated paper) with traditional screen printing techniques. When the transfer paper has dried, the decal is ready for use or can be stored indefinitely. The decal is applied by softening in warm water. The gelatinous skin with the embedd inmage releases from the base paper and can be applied to the ceramic ware. It is then fired to 700-750o C (1300-1380o F), at which temperature the glaze softens just enough to embedd the oxides.
The printing is done via a screen, which consists of a fine mesh, stretched on to a frame (usually wood or aluminum). The size of the mesh depends on what sort of results you want to get and also on the mesh size of the oxides in the medium. An image can be painted directly on to the surface of the screen with a suitable paint or shellac, or it might be transferred using a photographic emulsion. However this technique may require access to a special ultraviolet light for curing, although there are methods on the market for home users. Another method is to place a stencil beneath the screen. This saves making multiple screens, as the one screen can be reused with multiple stencils.
Once the image has been established, the medium with the pigments is drawn evenly over the mesh and onto the paper surface with a scraper. Scrapers are usually made of a thick slice of rubber held by a wooden handle.
Printing on to Tiles
It’s also possible to print directly on to tiles. In this case the whole decal making process becomes redundant and the result is much more immediate. Of course this is only possible on fairly flat surfaces. It would be difficult, if not impossible to print directly on to a mug, or a sculpture!