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Making Guide of the Ceramics

Materials & Clay Preparation

 

Materials

Materials

The raw material of the pottery is clay. The main substances of the clay are silicic acid (SiO2) and alumina (A12O3). Silicic acid can only be dissolved into a sticky liquid state at a very high temperature and the chemical reaction of alumina can reduce the melting point of the silicic acid. Because of the high stickiness, it can support the melting state of the silicic acid and prevent the clay from easily collapse.

Clay Preparation

The clay, which we acquire from the earth, must go through the clay preparation process of washing, abrasion, screening, and anhydration because it contains other organism and minerals. The moisture level after the initial preparation of clay has not been well mixed and still contains air bubbles. If it is used to mode into a clay body, the thickness will easily become uneven and the shape becomes curve and deformed. Once it is put into the kiln to fire, the air bubble within the clay body will expand and lead to cracking. Therefore, after the initial making of the clay preparation, the clay needs to be hand kneaded or by machine to clear away the air bubble and to ensure that the moisture and the hardness and softness are even.

 

Forming

Shaping is when the designer uses the clay to knead it into the shape that he/she desires. The major forming techniques are as follows:

 

(1) Hand building technique:

To use hand to knead the clay into the required form.

(2) Coil Method:

Coil Method

To role the clay into a rope-like shape and than to pile the clay tightly into the shape that it requires.

(3) Clay Slice Method:

To use the clay, using rolling and pressing, throwing, slicing techniques to form slices of similar thickness of clay and than using the clay to shape into the desire form.

(4) Wheel Throwing Method:

Wheel Throwing Method

To place the clay onto the center of the wheel turntable. First, to use both hand to beat the clay into the simple cone shape. Than, turn on the wheel, wetting both hands, moist the surface of the clay, than to push the clay using both hands starting from bottom toward the center. The clay piece will rise into a pillar shape. After repeating the similar action several times, the clay will become even and proceed into the next step by opening an aperture and shape into a hollow pillar shape, which can than be shape into all kinds of form and create the desired shape.

(5) Molding and Sculpting Method:

Molding is utilizing the above basic techniques by shaping the clay into the desire form. Sculpting is to sculpt lines on a formed clay body and eliminate excess clay and display a desired art piece.

(6) Grouting Method:

Grouting Method

Gesso is often used to make the model in which the mud is than pour into the gesso. Because gesso can soak up the moisture, therefore, the mud nearest to the gesso will first solidify. After the mud has hardened to a certain thickness, the excess mud will be poured out and only the hollow clay body is left. Except for the gesso model, small ceramic designer can also use the dry mud model or ceramic model after uncolored firing as the model.

Metal Tray Method

(7) Metal Tray Method:

To pour the clay into the hollow center of the gesso model onto the metal tray machinery and turn on the machinery to start the pressure. After the machine stops for a certain period of time, the clay body can be taken out. Because the gesso model can be used repeatedly, hence, this method can mass-produce the clay body.

(8) High-pressure method:

Using the high-pressure die, or industrial techniques of high pressure shooting of the mud to make the ceramic finished product.

 

Decoration & Glaze

 

Decoration

Decoration

Prior to the firing of the finished clay body, in addition to smoothing out the surface, it can also via plastering, impression, scraping and slicing, sculpting, and inlay techniques to add changes to the surface of the clay body and create different texture and lines.

Glaze

Clay body, which was put into the kiln for firing with no glazing, is defined as “uncolored firing”. Glaze is oxide mineral that consist of alkalinity, neutrality, and acidity. After high temperature melting into liquid state and cover over the clay body, it is not only water resistant, dirt resistant, and also alkalinity and acidity resistant. Because of the minerals encountering high temperature, it can display different color and added the color changes to the finishing product after firing. The major glazing techniques are as follows:

(1) Soaking Method:

To soak the entire clay body into the glaze chemical and take out immediately after. This will allow the glaze to be evenly distributed on the clay body.

(2) Pouring Method:

To pour slowly the heated glaze onto the clay body surface from the top to bottom using the wooden ladle and cup or other container.

(3) Painting Method:

To paint over the clay body surface by using paint brushes or writing brush.

(4) Spray Method:

Spray Method

To place the clay body onto the turntable, spray the glaze over the clay body using the spray gun or other spray equipment while turning the turntable at a regular speed. “Over Glaze” is to color draw after the glazing and firing and to reheat again. Famille rose glaze and gold glaze, are examples of this techniques. “Under Glaze” is to color draw the clay body and than to cover it with the invisible glaze and than put into the kiln for firing. Red, blue, and white copper glaze and red copper glaze are examples of this kind of techniques. Zinc, iron, cobalt, and titanium will melt among the glaze when encountering high temperature. As the high temperature within the kiln slowly cools down, the metals will partially gather together and result oxide crystallization, which becomes “crystal glaze”.

Firing & Finished Good

Firing

oxidate firing

Base on different requirements of the various products, the clay body is put into the electric kiln, gas kiln, or tunnel kiln with controlled temperature. After the clay body is being fired at the set temperature, the firing will be turn off and left to be cool off which is also the completion of the firing process. Base on the different needs, there are different firing method and number of times to be fired. There are two types of firing, “oxidate firing “ and “reduction firing”. Oxidate firing is when during firing, the inside of the kiln is being feed plentiful of oxygen it needed. While firing, the inside of the clay body are still left with traces of oxygen. Generally speaking, the electric kiln and gas kiln can accomplish this kind of effect. Reduction firing is when the temperature inside the kiln has reached the set temperature; it will stop the supply of oxygen into the kiln and allow the fire to continue to burn from the traces of oxygen left over within clay body or glaze.

reduction firing

The oxide metal within the glaze will change and display different colors. This kind of firing requires gas kiln to accomplish it. Base on the number of times of firing, it can be divided into uncolored firing and glaze burning. Uncolored firing is when the clay body is place within the kiln to heat around 800℃ – 900℃; the clay body will harden and becomes water resistant. Because it has absorbed the moisture, it is more advantage for glazing. Glaze firing is when the clay body has been glaze after the uncolored firing and replace into the kiln at the temperature of 1200℃ and above.

Finished Good

Finished Good

The differences with pottery and porcelain are the number of impurities within the clay and the high and low temperature of the firing. Less impurities requires 1200℃ and above firing temperature. After the firing, the finished good have high transparency, low ventilation, low moisture absorption, light and thin quality, clear and sharp sound, bright color, and are made into porcelain such as vase, bowl, and plate. Vice versa, clay with high impurities, because the oxides in the midst of the impurities are helpful to the firing, the required temperature is around 1100℃. The finish goods have low transparency, high ventilation, high moisture absorption; thick and solid, low and turbid sound, and are made into pottery, such as cookware and Koji ceramic.

Conclusion

Ceramic making seems quite easy; however, it is actually a high level techniques and firing creativity industry and art. It is a wish that through this document, it will open your door to ceramics and allow you to understand all the questions you have. As to the answer, with the accumulated years of experiences and abundant creative spirit of Yingge ceramics makers and its sellers, it will take you one step further to fulfill you need for knowledge. Need is the drive behind the practical techniques and art creativity. It is a wish that you are not stingy with the “collection” of the product and artistic piece of this town and allow this town to become well known for its ceramic art and to take one level higher and to overweeningly look at the world.