MIXING YOUR OWN CLAY

Mixing your own clay offers the intangible benefit of being completely involved in the pottery endeavor. Many people first started to realize their artistic goals in ceramics and, for  them, the whole activity of mixing clay and making pots or sculpture are intrinsically tied together. Monetary rewards and the breakdown of production costs are not relevant factors in such situations. For potters pursuing a total involvement in all aspects of ceramics, the process is equally as important as the final product.

One major advantage of mixing your own clay is the ability to customize clay bodies. Giving you greater flexibility in adjusting the clay body formula and moisture content, which gives you overall quality control. However, carefully weigh whether the process is worth the labor, effort, and expense.

Before mixing your own clay, ask yourself: Does the clay body depend on a specific finished color? Do the forming qualities of the moist clay require an exact clay body for­mula? Does the clay require a specific moisture content? If yes, consider mixing your own clay. For example, clay bod­ies containing nylon or fiberglass fibers used for structural strength are difficult for ceramics suppliers to mix, due to the time-consuming process of cleaning clay mixers and pug mills. Ceramics suppliers are not set up to mix such custom formulas, leaving potters to mix it themselves.

Another advantage of mixing your own clay is that, as long as you have the raw materials on hand, you’ll have a ready supply of moist clay. You can mix the amount of clay desired and control the supply, which is especially important in a production situation.

A third advantage of mixing your own clay is that you can mix and test a variety of clay bodies and make timely revisions to clay body formulas. However, understand  that mixing your own clay will require knowledge of raw mate­rials and the ability to formulate a clay body.

 

MIXING EQUIPMENT

Mixing your own clay can be capital intensive: it requires the purchase of clay mixers and pug mills. An added cost is inevitable maintenance and repairs. The money you spend to buy and maintain a clay mixer and pug mill could be spent instead for other purposes that might return a greater profit. If you try to get by buying smaller clay mixers and pug mills, your unintended result could be slower clay production and possibly higher maintenance costs with underpowered, inadequately designed machines. But if you buy larger machines, they’ll cost more upfront, and can result in unused production capacity. That’s why it’s important to take time to research and find the best machines for your individual production requirements.

MIXED CLAY STORAGE

If you mix your own clay, you’ll also need to purchase and store your materials. Plan your dry clay orders so a steady supply is always available, causing no delays in mixing operations. Buying in bulk results in a lower cost per pound of materials, but you also must have the space to store dry clay. Designate areas close to your productions space for clay mixing and storage for dry and wet clay. This will save labor and time and, remember, the more you touch the clay, the more it costs.

 

Get Equipped to Mix Clay

Simply mixing the dry clay body formula and adding the appropriate amount of water is all that is really required to achieve a plastic mass of usable clay. Traditionally hand mixmg or blending days and other ceramic raw materials was the only method available lo achieve workable consistency cloy. Today, hand mixing clay will accomplish the goal, but mixing machines and pug mills will save labor and lime when you require greater quantities of uniform-consistency, moist clay.

Whatever method is used, each clay platelet should be surrounded by a film of water with the other raw materials in the clay body blended into a uniform mass. for optimum plasticity.

CLAY MIXER AND PUG MILL

The most efficient and popular way to mix clay is with a clay mixer and pug mill. Ceramics supply companies use both machines in their productions. Specific amounts of dry clay and water are blended in the mixer, and then the moist clay is placed in the pug mill and compressed by a mechanical screw. The compressed clay then goes through a chamber where the air is removed, and then the clay is extruded out of the pug mill nozzle in a usable condition.

The compaction of the clay causes a denser fired clay body. Compacted clay platelets fuse faster and more com­pletely during the firing than noncompacted platelets.The extruded clay can average 20 percent moisture before it is placed in plastic bags.

FILTER PRESS

Dry clay body formula is mixed with excess water to form liquid slurry. It is then pumped into a series of absorbent leaf-shaped bags. As the bags are compressed, excess water is pressed from the liquid clay. The leaves of moist clay then can go onto the pug mill for further mixing and de-airing. In filter pressing, each clay platelet is effectively surrounded by water in the slurry stage. The water-soaking period produces greater plasticity in the clay than other mixing methods. The filter press procedure is costly and time-consuming for a ceramics supplier to use in produc­ing moist clay. Individual pot ters would further incur higher production costs using the filter press method.