Understanding the different stages of clay is essential as you begin to craft your first pots, plates, bowls, and other vessels.
The stages of clay are what take your work of art from point A to point B.
In this beginner’s guide to pottery, we take a walk through each step in the process. From the wettest form of clay at the beginning all the way to the hardest state at the end.
Let’s uncover the transformation that results in a final product that is ready to be enjoyed.
Foremost, there are many different types of clay. Earthenware, stoneware, ball clay, and porcelain are among the most common. However, there are thousands that you can choose to use for your next pottery project.
Your choice in clay depends on the type of pottery you wish to make, what equipment you will use, and the temperature at which you will fire. There are also commercially available clays that you can purchase from the store or learn to mix your own.
Either way, whether store-bought or handmade, this clay is your ground zero. It is the first stage of clay in the process.
Stage Two – Slip
Slip is the wettest form of clay that has the highest moisture content.
Simply adding water to old clay will make slip, which is a runny, liquid mixture that resembles a slimy mud-like substance.
Slip has numerous uses in the production of pottery. Its primary use is to act as a glue or an adhesive that bonds separate clay objects together once dry.
To apply slip and attach two pieces of clay together, you must first score the surface of one piece of clay, which means to create hatch marks or scratches on a specific area. You will then apply slip to the area and, finally, adhere the second piece of clay to the first.
Slip can also be used for decoration by brushing or painting colored slip across the surface of the pottery.
Stage Three – Plastic
The plastic stage of clay is also referred to as the workable stage.
Some of the moisture has evaporated in the plastic stage. The clay can now be manipulated into different forms, either by hand or by using a pottery wheel.
In the plastic stage, the clay is flexible and can be molded into any form or shape you desire.
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Stage Four – Leather Hard
The clay in the leather hard stage now has less moisture content, making it drier and sturdier, yet still slightly flexible. It will hold your form from the plastic stage in place.
In this stage, clay is either soft leather hard or stiff leather hard. Soft leather hard is an excellent stage for attaching other pieces of clay together with slip. Stiff leather hard is useful for carving and trimming.
Stage Five – Bone Dry
The bone dry stage entails the clay having zero moisture and is completely dry to the touch with a lighter color. Leaving your clay out to dry for a week or more will bring you to the bone dry stage.
It’s important to remember that at this stage, the clay is extremely fragile. As much as possible, you should avoid any touching, handling, or transporting of your clay project when it’s bone dry. Your project cannot be repaired if broken at this stage!
On the other hand, old, broken off pieces of bone dry clay are perfect for making slip when needed.
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Stage Six – Bisqueware
After your project is completely dry at the bone dry stage, it can be placed in the kiln for the first time. Firing your project in the kiln for the first time is called bisque firing and occurs at cone 06 to 04, or around 1900 degrees. Once fired, your project is no longer clay, as the kiln transforms it into a new, firmer substance called ceramic.
Like the bone dry stage, a bisque fired piece cannot be repaired if broken. It is still slightly fragile. The porous and absorbent quality of the bisque fired piece makes it perfect for glazing.
Glaze is made up of five components, silica, clay, flux, colorant, and water, which soaks into your bisque fired piece easily and quickly. Glazinghttps://en.wikipedia.org/wiki/Glossary_of_pottery_terms, either through brushing or dipping, will bring your project to life with a glassy, smooth, textured, matte, or clear finish.
Stage Seven – Glaze Firing
After your glaze dries, your piece will go back into the kiln for its final firing, otherwise known as glaze firing, or the last stage of clay.
Glaze firing can occur at different temperatures, and it’s essential to know at which temperature your project must fire.
- Earthenware clay is a low fire clay, and the correct temperature will be around 1800 degrees, or cone 04.
- Working with stoneware to create objects such as plates, bowls, or other food-safe items, requires mid-fire, between cone 5 and 6, or around 2250 degrees.
- When working with porcelain or other pure forms of clay, the temperature will be high fire, or cone 10, which is around 2380 degrees.
Note that if temperatures in the kiln are too high, your piece may melt, and if they are too low, it can’t properly fuse together or vitrify.
It’s further important to select glazes that can fire at the correct temperatures. Depending on the type of clay you choose, make sure you also choose a glaze that can fire at the corresponding temperature. For example, your glaze can melt off of your piece at too high of a temperature.
After the glaze firing stage, you have completed your last stage in the clay process, and your project is ready to be enjoyed!
As we move through each stage of clay in the pottery process, we see less and less moisture in the clay. As the clay dries, your project becomes slightly smaller and smaller. Meaning, when you first start molding your piece, the finished result out of the kiln will be smaller, so it is important to note this distinction at the first stage, so you can correctly size.
Furthermore, as drying occurs in each stage, it is crucial to allow drying to take place over the right duration of time. Drying too fast can lead to cracks, especially while your piece is in the kiln. Drying unevenly can also lead to breakage, so it’s important to make sure that your clay is evenly spread out throughout the object. For example, when crafting a pot, if the bottom is thicker than the rim, the bottom will take longer to dry and will likely crack. Therefore, your goal while molding should be to create equal thickness.
Overall, through understanding the stages of clayhttps://artofed-uploads.nyc3.digitaloceanspaces.com/2017/06/ClayCenterVisualsStages-2.pdf, you can have more control over your pottery. Knowing moisture levels and how much water affects each stage can help you to remain or move from stage to stage at the appropriate time. As you become more conscious of each of the stages of clay, your pottery and final products will continue to become more and more successful, leading you from being a pottery beginner to a pottery master in no time!