October 26, 2001, Newsletter Issue #61: Users` Questions 4

Tip of the Week

Question:
How do you make, decorate, and paint ceramic tiles?

Answer:
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 difficult. In this feature, I would like to take a brief look at some of the issues involved. For those wanting to actually get out there and do their own printing, I would like to refer you to some of the technical literature on the subject available in many good technical ceramic books and magazines.

Decals
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 screenprinting 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 embedded image 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 onto a frame (usually wood). 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 onto the surface of the screen with a suitable paint or shellac, or it may be transferred using a photographic emulsion. However, this technique requires access to a special ultraviolet light for curing.

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 Onto Tiles
Itīs 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 even a sculpture!
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Question:
What clay types are available?

Answer:
The clay body selected for throwing is as important as the type of wheel and wheel head used. There are three general groups of clay bodies - red or white earthenware, stoneware, and porcelain. Stoneware usually has the best working properties, because it is not always as workable as an earthenware body, and porcelain is generally considered a poor clay to use when learning to throw.
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Question:
You stated to use a Fine Nylon Tulle a Sander Sponge to clean the seam lines on a slipcast ware. Where could I buy these to try? Thanks.

Answer:
Fine Nylon Tulle is readily available at fabric supply stores, and sander sponges are found cheaply in most $2 stores or at any hardware store.
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Question:
Can I draw directly onto a pot?

Answer:
You can draw directly onto a pot by placing design over carbon paper and tracing the design, you can also sketch right onto the surface with pencil as the lines will burn out in the firing. Hope this has helped!
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Question:
How can I transfer an image to a pot?

Answer:
The best way to transfer images, if they are of volume, or for production ware, is to screenprint. This is done by taking a photocopy of your design, and making a screen, this procedure can be found on my site. Hope this has helped!
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Question:
How do I dry my molds?

Answer:
The best way I have found to dry molds is to place them in the sun for a few days...if you want a quick dry, however, try the oven. Donīt heat over 150c as will weaken the mold, but a few hours in the oven will do wonders. Hope this has helped!
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Question:
How do I make terrasigillata?

Answer:
Terrasigillata - Using a glass or clear container, dissolve 5 gms of calgon sodium hexametaphosphate (which is a deflocculating agent), in 2 pints of rainwater (sodium carbonate or potassium carbonate can also be used). Add 230g of dry, crushed clay, sieve through a 60 mesh (or finer). Shake container, mix and leave for three days minimum. The clay will settle into 3 layers with a layer of clear water on top, siphon off this clear water and discard. The next layer is the terrasigillata (colloidal slip). Note: White clay needs 0.3% sodium silicate...and water to clay ratio of four to one, to deflocculate. Red clay needs 0.5% sodium silicate...and water to clay ratio of three to one to deflocculate. Terra sigillata is high in alumina. It may be hardened by adding 3-4% sodium silicate to the recipe after deflocculating the sigillata. Hope this has helped.
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Question:
I have a ceramic chinese figurine with chinese markings. Where can I find out the value?

Answer:
You did not mention where you are from, so my suggestion, for a valuation on an item, is to contact an auctioneer close to you. If he doesnīt do it himself, he is sure to know someone in your area, who does. I hope this was of help!

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