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On Thursday, July 29th we visited the Ungheni Ceramic Factory. It took me back to the Ceramics class I took at OCU, with amazing professor Joe Smith. Compared to our little studio, this was so huge!   They mass produce different ceramic containers of all kinds. There are many pieces that are made from molds, and then many handcrafted pieces, or specially designed pieces as well. We got to watch several masters on the Potter’s wheel, and my mind was again flooded with the parable of God being the Master Potter. There is so much symbolism in this process!!!

 
The point of this blog is for you to see more of who God is; it’s not just a wikipedia entry. (although wiki did help me with some of it! 😉   As you read this description of ceramic processing, think about God being the Creator and you being the clay.  Let Him speak to you through it!
 
Ceramic processing is used to produce products that are very diverse in size, shape, detail, complexity, and material composition, structure, and cost.  The purpose of ceramics processing is the natural result of an increasing ability to refine, develop, and characterize ceramic materials. 

Ceramics are typically produced by the application of heat upon processed clays and other natural raw materials.  Ceramic products that use naturally occurring rocks and minerals as a starting material must undergo special processing in order to control purity, size, clay distribution, and depth.  These attributes play a big role in the final properties of the finished ceramic.  

 
 

The next step is to form the ceramic particles into a desired shape. This is accomplished by the addition of water and/or additives such as binders, followed by a shape forming process.  Some of the most common forming methods for ceramics include extrusion, slip casting, pressing, tape casting and injection molding (on left).   Many early ceramics were hand-built using a simple coiling technique in which clay body was rolled into long threads that were then pinched and beaten together to form the body of a vessel. In the coiling method of construction, all of the energy required to form the main part of a piece is supplied indirectly by the hands of the potter. 

The Potter’s wheel technique permits the energy stored in the wheel to be finely directed to where it would be most effective, at the point where the hands of the potter come into contact with the ball of clay located in the center of the spinning disk. Unlike hand building, in wheel throwing, the bulk of the energy used comes directly from the hands of the potter. The introduction of the fast wheel brought benefits in the form of speed, and a job that might have taken hours, or even weeks, to complete was reduced to one that could be done in minutes.

There are many techniques in use for throwing ceramic containers, although this is a typical procedure: A round, moist lump of clay (that’s already been purified) is thrown down onto the wheel head or a bat (wooden board) attached to it. The lump is made even and forced to the centre of the wheel by applying pressure with the hands. The thrower finds the center of the clay by moving a thumb across the lump until no more friction is felt. The thumb is pressed into the center of the lump, stopping about 5 mm from the wheel head. The hole thus made is widened. The sides thus defined are pulled up and made thinner by pressure between the hands. The vessel is shaped, and the mouth is smoothed. The vessel is cut from the wheel head with a cheese wire and left to stiffen. Sometimes the stiffened vessel is inverted on the wheel and trimmed with a sharp tool. A skilled potter can quickly throw a vessel from 15 kg of clay.  Alternatively, by throwing and adding coils of clay then throwing again, pots up to four feet high may be made.

After the shape is formed, these “green” ceramics undergo a heat-treatment (called firing) to produce a rigid, finished product. There are many ways a piece can be fired; firing is an art in itself.  Some common styles are Raku firing (on right); Wood firing, and the firing using a kiln.

Drying the Ceramic: A Ceramic kiln helps remove all of the trapped water from ceramic wares prior to firing or during the firing process. Ceramic contains crystal bound water that cannot simply evaporate and a kiln is used at low temperatures to dry out the ceramic. This process is known as a “bisque” or a “single” firing and the resulting ceramic is chemically different and ready for complete firing at higher temperatures.

Firing the Ceramic: When the kiln is used for a full firing of ceramic, the high temperatures of the kiln change the actual particles of the ceramic from clay into finished ceramic. First, a process called burnout begins in which the ceramic is heated to the point at which all impurities are burned away. Second, a process called sintering happens, which means that the particles of ceramic bond to each other and the ware becomes waterproof and structurally stronger. Finally, and at higher temperatures, decomposition occurs, where the basic oxide particles of the ceramic are broken down. (picture: a modern industrial sized kiln)

Glazing the Ceramic: The final stages of making ceramic using a kiln involve glazing the ware in order to seal it and give it a finished look.  Not all pieces are glazed, but products such as electrical insulators, dinnerware and tile usually undergo glazing.  This involves a process called vitrification in which the ceramic ware is heated to such high temperatures that the oxidation of the exposed ceramic increases so high that the quartz crystal structures with the ceramic actually melt and flow together giving the finished glazed ceramic product its shiny polished look.  Some ceramics for advanced applications may undergo a machining and/or polishing step in order meet specific engineering design criteria.

www.wikipedia.com  “The Potter’s Wheel.”