Making pottery on a large scale is like any other business. People come in early and start to work. As a pottery maker you need to plan your day. It usually starts with asking the question what is being made that day and is there enough raw materials, clay. Then goes into asking the question about preparations. What is the prep that needs to happen before work can actually start on the clay. As pottery is being made there are different stages the clay goes through and those stage areas needs to be prepared ahead of time to ensure when the clay arrives all the tools and equipment have been staged and is ready. Depending on the design you can’t have clay sitting around while someone is preparing the next area for the clay. Depending on the humidity clay can dry out and then be in a different state than it was say a hour ago. This is why timing is important. All this prep work and the work itself has a rhythm. It’s pre planning, thinking ahead, and sometimes even team work is necessary.
First step in making pottery
Usually one of the first steps is to run the clay through what’s called a Pugmill and or Clay mixer. In a nutshell this machine gets out all the air bubbles. Over time there is rock that decomposes under the Earth’s heat and pressure to form tiny little flat particles which are plastic or having plasticity. This is the softness of the clay.
Many of the bigger pottery shops have a Pugmill. Most smaller shops do not have this luxury and will beat the clay by hand to get out all the air bubbles. Pugmills are fantastic machines that are specifically designed to mix clay from scratch. They are expensive machines but save a ton of hand labor and thus the investment is worth it especially for larger shops that make a ton of pottery. These machines pay for them selves in several ways. First off by recycling clay pieces and by speeding up the process. A pottery shop can end up with many pounds of clay scraps. These scraps then will be run through the Pulmill and a nice new looking piece of clay with no air bubbles will be created. This entire subject regarding Pugmills can fill an entire book so we only scratched the surface here about Pugmills. So just know this, there are many different types and there are ones that can mix clay only and others that can do wedging. In addition the clay needs to be in a particular condition before it can be run through the Pugmill. Either stiff, slurry or maybe bone dry. In addition as with any machinery Pugmills can be dangerous. The large ones have large motors and draws a lot of power. There is a lot of torque needed to bend and move clay. You definitely do not want to come in contact with any of the moving blades.
How an Extruder is used when making pottery and ceramics
Smaller shops will run what is called an Extruder. These are simple but powerful machines that can hold about 25 pounds of clay scraps and produce extrusions of up to 4 by 4 inches or so. These machines are entirely hand driven. There is usually a large handle that is turned that drives a rack-and-pinion gear box that reduces the force necessary to create an extrusion. Usually the good machines require about thirty pounds of force to make an average extrusion.
Moving and bending clay is something humans have been doing for thousands of years. After the clay has been run through the Pugmill or beaten by hand it’s now ready to be shaped into it’s desired thickness. Another tool is needed called a slab roller. These clay machines are much like the old fashioned washing machines where the clay is squeezed by two rollers. The rollers have a small diamond pattern or knurling which is machined into the roller. This aids in the gripping of the canvas that covers the clay. The roller presses out clay that can vary in thickness from paper thin to over 2 inches. This gives great flexibility when making slabs of clay. Slab rollers can produce very thin translucent porcelain slabs to very thick heavy slabs very easily. Most table top slab rollers are made from melamine or have a melamine surface for moisture resistance. Shops that do not have a slab roller will have to roll out the clay slab by hand and this is very labor intensive and very hard to get a consistent thickness. Larger shops will have an electric slab roller and table. This is a fantastic machine for a potter who needs to roll out a large number of slabs per day. The clay slab rollers produce perfectly compressed uniform clay slabs effortless. Theses machines are driven by massive 4 inch rollers and number 40 chain and sprocket for maximum strength for heavy loads.
How a Slab Roller is used in making pottery and ceramics
The clay is covered with a canvas and then is pushed through the slab roller and out of the other end the clay comes out perfectly the right thickness for the design. For our example, in this article I will assume we are creating a plate. When the clay comes out of the slab roller it has a canvas imprint pressed into the back of the clay. For making a plate this is not desirable so the clay is prepared and the canvas imprint is removed by hand. This requires using a flat tool and run along the flat surface of the clay several times thus removing any canvas imprints.
Templates are critical for pottery and ceramics
When making pottery plates a template is created for the exact dimension of the plate. The pottery pale template is usually bigger that the desired plate size due to shrinkage. During the firing process clay will shrink. So if making a 10 and one half dinner plate then the template will be a little larger than 10 and one half inches in diameter. So in a large shop the “Forming” team will do this work. The template will be their guide. The forming crew will take each slab and will cut out the plate using the template and will stack the clay in different groups according to their diameter.
Different types of clay
There are different types of clay, earthenware, stoneware and porcelain. Earthenware is still porous. These are like terracotta pots you see for sale. And porcelain is like a pure form of clay and is similar to stoneware in that is if fired at a higher temperature. These clay’s are very hard and have very low absorption. Most dinnerware is stoneware which is a harder product and which is of course less porous and great to eat off of. Stoneware creates a great finish and is a very durable product.
Pottery and ceramic molds
The clay is then set into a mold to get the final shape. Many large plate shops use plexiglass to help form their plate shapes. Smaller shops just form the shapes by hand. So the number of molds the shop has the number of different variety of plates a shop can make. The mold is then pressed into the clay forming a uniform plate. Each plate is exactly like the previous plate. So for the artist this is boring making hundreds of the same exact plate. A nice steady pressure is needed to remove any air bubbles. Any bubbles left in the clay would warp the clay when fired. When working with clay it’s all about using pressure to form the clay into your visions if an artist or your mold if a craftsman making hundreds of plates. It’s also about taking your time and not to rush. The clay has a mind of it’s own and has to be coached into it’s final form.
The beauty and art come in where each plate is one of a kind. The plate has the hand made touch that can not be readily repeated. Many larger shops use what’s called Jiggering to form their plates. Jiggering is a process of spinning a mold and as the mold is spinning a tapered template is pressed into the soft clay. This is a fantastic way of mass producing simple shapes on a spinning pottery wheel having a swinging arm with a template. For this process to work well the clay is typically much softer than what is used on a throwing wheel or potters wheel. Many large shops will use another process called RAM processing which is much better but more expensive.
RAM processing of clay involves a mechanical hydraulic press that presses the clay into shapes using dies. The end result is a higher quality clay plate for example. The steps used for RAM processing results in a very uniform piece of ware and saves money for the shop by having less rejects during the firing process in the kiln. The press time is the same for each cycle therefore the pressure is not left to guesswork. Pressure is very accurately controlled therefore glazes look consistent and it all adds up to a higher quality product. There is of course a lot more to RAM processing of clay than what I have described here. There is enough to write a book. There are pressure requirements, RAM dies which usually consists of both a male and female parts, shapes and the actual production.
Most pottery shops will strive to complete the entire pottery process within their own shop and not have to contract out any of their work to larger shops with bigger and better equipment. But sometimes it becomes a trade off between creating the order on time and having to contract out certain pieces and parts to get the order ready in time.
Leather hard clay
After the clay has dried for about an hour or so, depending on the humidity in the air, the clay then becomes as what is known as leather hard clay. In this state the clay is still wet but firm. The clay is still workable so any trimming can be completed while the clay is in a leather hard state. The plate can now be looked at and any imperfections can be addressed and corrected. The outside of the plate is looked at and is smoothed out to perfection.
The pottery plate is now ready for the first firing which is called the bisque firing. This is usually about a twenty four hour process. The pottery is placed into a kiln and subjected to a high temperature which burns off any organic material and removes water in the clay. The temperature is usually about 1800 to 1900 or so degrees. What comes out of the kiln is bisqueware and is ready for glazing.
The glazing process for clay
Glazing is a very important step in the pottery creation process. If the glaze is messed up then there maybe no way to save the piece. Glaze is made up of clay, glass, flux, color and other minerals to give it that colored special look. Glazes also come in a shinny look and also in a matte look and a wide range of colors. Some shops spray their glaze on with a compressed air paint gun and others use a dipping method where the entire clay piece is dipped into the glaze. A good smooth look is dependent on the bisque. If the bisque has small pin holes and is uneven then the glaze will not look as good. A good glaze depends on having a good bisque. If there is dirt or other derbies on the bisque then the glaze might not sick to the bisque. Glaze usually dries very fast. So fast you can watch it dry while looking at the clay piece.
A second firing for pottery and ceramics
Now that the glaze has been applied it’s time for the second firing. The second firing is where the glaze and the clay is fused into each other and melted into one piece. The end result is a very strong stoneware product. During the second firing the temperature can vary but is usually around the same as the first firing or a little hotter. Clay becomes pottery at temperatures of about one thousand degrees. Most tribal earthenware is fired to about fourteen hundred degrees Fahrenheit. In modern kilns temperatures can range form about 1800 degrees to 2400 degrees. So for example, a modern toilet is fired to temperatures between 2300 to 2400 degrees making it very hard and strong. Usually during the firing process the original clay will shrink anywhere from 14 to 20 percent.
What is cone 6
Most shops will purchase clay that is made to fired at what’s called cone 6. The cone process is a way of measuring both temperature and time. So cone 6 translates to a temperature of about 1828 degrees to 1855 degrees and is for bisque and low glaze firing. During the firing process bringing down the temperature is critical. The temperature in the kiln can’t just be turned off. The temperature has to be brought down in a controlled way otherwise the bisque will shatter into pieces. The controlled cooling cycles bring out the color and texture of the ceramic piece. This cycle also helps with the crystallization of certain materials in the clay and glaze in return gives depth and much interest to the glaze.
Pottery and ceramics conclusion
One of the most anticipated times is when the kiln is opened after firing. You never know what you are going to get and sometimes it’s a big surprise. This is especially true for artists who are experimenting with different textures and colors. For pottery shops is pretty much the same because it’s already been done a hundred times before.
As an artist you let the ceramic piece speak for itself. For a ceramic shop you let the materials speak for themselves and always ask the question how does the plate look on the table with food on it. The biggest challenge for pottery shops is, can they continue to produce the same high quality plates that look exactly the same year after year. And the challenge for the artist is can a new piece that looks entire different from the last artwork be created and be loved. As a consumer you are looking for a high quality product or artwork that you can’t get just anywhere and has a look and feel to it that you fall in love with. If you are interested in purchasing pottery or ceramic art in Murfreesboro,TN then click here to go to ceramic wall decor: https://www.ceramicwalldecor.com/