Ceramic - Pottery Dictionary

by Susan Mussi

ca: OFICIS - Rajoles que il·lustren les formes de treballar. (EN CONSTRUCCIÓ)

es: OFICIOS - Azulejos que ilustran las formas de trabajar.(EN CONSTRUCCIÓN)

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Occupations are one tile designs that illustrate, with figures, the different ways of working. They are painted with the Majolica method, which was brought to Spain by the Arabs. When the Arab influence declined it became an illustrated method of informing the illiterate pubic.

In the past the size of the tiles was 13×13cm and are now 15×15cm. They depicted workmen doing everyday jobs; glass blowers, carpenters and barbers. There are hundreds of designs and the different ones illustrating the same subject are joined together to form a large picture, showing the different stages of work; making wine, bread, oil and many other specialties.

The method spread along the Mediterranean coast and there was many small businesses that went through the whole process, from digging the clay out of the earth to taking the finished pieces to be sold at the local towns and markets and many had their own illustrative way of signing their work, one was the way the birds were painted.

In the first three photos show a) Lady with washing; b) Barber; c) Glass blower and the next are pictures that tell the stories of d) Making wine; e) Bakery; f) Making bread

Remember all one tile design of the same size can be mixed to make the picture you want to the size you require.

To see more go to occupations and collections in my web

ca: OCRE

es: OCRE

Ochre is an earth color, the base of which is yellow. Red and brown are added in different intensities to give different shades.



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Omelet plate is a special Catalan plate made for turning and serving omelets. Usually, the most common omelet is one that has potatoes and onions as ingredients. In a frying pan, they are cooked until soft and then the beaten eggs are added. When the base of the omelet starts to get solid but the top is still liquid, the omelet plate, held by the leg like a lid, is put on top, pan and plate are held together and turned over. Your omelet is now on the plate, you can eat it as it is or slide it back into the pan to cook it a bit more.

The words on the plate say Tomba Truites which means Turn Omelets in Catalan.

ca: SOBRE ESMALT - tercera cocció

es: SOBRE ESMALTE - tercera cocción

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On-glaze is when an already fired glaze is decorated with ceramic colors and fired again. The work must be fired three times, bisque, glaze-base and decoration. There is a large range of commercially prepared colors that can be fired between 700º C and 850º C and they can be bought in the form of powder, liquid or small blocks. Work can be decorated, fired, then have more colors added and re-fired at the same or lower temperature; this does not affect the colors of the first firing. In many countries this method is known as “Porcelain Decorating,” not because it is put onto porcelain ware but because it is painted using a similar method.

The problem with painting onto a fired glaze is that colors cannot adhere to it, so they spread, run and separate while you work. You can counteract this by putting a thin layer of gum-Arabic on the place you are going to decorate or repair; this holds the colors and when fired, it burns away, leaving the colors fused to the surface. It can also be done by mixing the colors with an oil medium or varnish and turpentine.

If you prepare your own colors you must be sure that the powder is dry, as the products they are going to be mixed with will not tolerate water. If damp, spread the powder out on a piece of newspaper and put it in a warm place to dry out.

Working sequence:
1) Either an oil medium or varnish can be mixed with the colors. The varnish is the ordinary, colorless one used to paint wood.
2) Prepare the varnish in the following proportions: 1 part varnish to 3 parts good quality turpentine, which you should buy it at a chemist. When prepared, keep it in a bottle that shuts well. Do not make more than you need as it hardens.
3) Prepare the colors needed in the correct proportions and mix them with oil or varnish.
4) On a non-absorbent slab, using a palette knife, mix them together until they are completely integrated and have a thick smooth texture.
5) Mark the prepared design onto the tiles with charcoal powder or carbon paper. If charcoal powder, do it when the work has been covered with a thin layer of gum-Arabic, so it adheres to the tiles.
6) Paint on your design using the prepared colors; some colors might need two coats.
7) Leave to dry for about 12 hours.

8) When the decoration is finished and completely dry it can be left as it is, or covered with a thin layer of transparent glaze. In the former case, the difference between the first and second firing can be noticed; the decoration and the base are not at the same level and this can be seen and touched. To avoid this, cover the whole work with a thin layer of transparent glaze using a large, soft brush and taking care not to damage the decoration. This will leave a thin white coat; it may be thicker in some parts where it overlaps, but this is of no importance, as when fired it will have a smoothly integrated finish and touch, like an in-glaze.
Fire it at the heat the colors you are using are prepared for.

Both pictures below were prepared with a crackle glaze-base and fired. They were then painted using the on-glaze method but with colors prepared for working with the Majolica Method. Everything is done in the same way as explained above, except it must be fired at 980º C; we do this so it can be fired with other work we create using the Majolica Method and there is no need to wait to fill up the kiln to fire at a lower heat. After the colors were fired, the tiles were rubbed with a prepared dark color so it integrated into the cracks, then with damp cloth all the surplus paint was cleaned off; this leaves the cracks dark, so they can be seen.
Read more about: In-glaze / Underglaze / Transfer



Once-fired is when slip glazes are applied to dry ware and they are fired together. Ware is completed in one firing, clay and the decoration together; this includes both slip and glazes.



Opacifier is the name for a substance that, when added to a glaze, transforms a transparent glaze into an opaque one. Two opacifiers are tin oxide and zircon.

ca: OPAC


Opaque is when a glaze or color is not transparent, it prevents light from going through and this hides the color of the product it is covering.



Open is when a door, lid, drawer, etc., is not in a shut or closed position so the interior is accessible. In the photo, the lid of the kiln is open.



Orton: Edward Orton (1863-1932) an American ceramic engineer who worked on pyrometer cones. The Orton cone was named after him and is the name of a USA firm that manufactures cones.
Read more about: Cone – Grading / Cone – Pyrometric / Cone – Sockets / Cone – Witness

ca: UNÇA

es: ONZA

Ounce is the name of a weight measure used to weigh small articles, the word is used in many countries but in each one it applies to a different weight. On January 1, 2000, it ceased to be a legal unit of measures within the United Kingdom.



Oval-ware refers to oval shaped pieces of pottery, plates, decorative and kitchenware used for cooking in the oven or on top of the heat, like casseroles, etc. and designed to bring food directly from the oven to the table.

They can be made using molds or by wheel. When made on a wheel they are round and to change the shape, the clay along the center of the floor is cut out, as illustrated in (a) above. The two sides parallel to the cut are pushed together and joined to make an oval shape. Put a coil of clay along the joint, press it down and smooth off the surface. Leave it and when it is dry enough, turn it and repair the back in the same way.



Ovenware is the name for heat-resistant dishes for cooking food in the oven, like casseroles, etc. They are designed to move food directly from the oven to the table.
Read more about: Flameproof ware



Over-fired is when a clay, glaze or glaze colors have been fired at a too high temperature. Clay can disintegrate, become liquid and damage or destroy the inside of the kiln and everything in it. Colors and glazes become matte or burn away completely.



Over-glaze: also known as on-glaze, is when an already fired glaze is decorated with colors and fired for the third or fourth time.



Oxidation is an evolution during firing that allows enough oxygen for clays and glazes to react correctly; an electric kiln always gives an oxidizing fire.