Sculpting: Clay Types

Open any how-to book on a new skill and the first few chapters will most likely contain the history of the skill, its definition, tools commonly associated with it and so on. All of that to say there will be a few chapters of information before it covers the actual process of how to go about achieving the skill.

These articles will be structured in that same way. We’ll cover some basic knowledge that any sculptor should know, like clay types and their characteristics, sculpting material, sculpting techniques, and so on. I am learning as we go, too, so if you’re a beginner sculptor like me we’ll be in the same boat.

Before we begin, “to sculpt” is defined as a verb that means to “create or represent (something) by carving, casting, or other shaping techniques.”

As I mentioned in the previous article, sculpting can be done with other materials besides clay. The reason we’re focusing on it in this article is because clay is the most common and it’s the easiest material to start beginning sculpting and work up to more advanced techniques on.

Clay comes in many forms, no pun intended, and different types are suited best to certain techniques. It’s helpful to learn all of this before you even begin sculpting. Below are various types of modeling clay and their characteristics.

Modeling clay

  • General term that covers a group of malleable products used for sculpting and building by children, art students, hobbyists, and professional potters and animators
  • All types can be shaped and worked with tools for sculpting, blending, texturing, thinning, scraping, poking, and cutting
  • Can also be rolled with rolling pins or in pasta makers, molded, and worked with tools such as extruders, potato mashers, and garlic presses to create various shapes
  • Can be built up on its own or built onto a pre-formed armature
  • Below are some basic types

Oil-based (Plasteline) modeling clay

  • Scientific names: plastilina or plasticine
  • Invented in Germany by Franz Kolb in the 1880s and independently by William Harbutt in England in 1897
  • Its properties include: stays soft and workable, unlike pottery clay and way; neither hardens nor dries; comes in a wide selection of colors that can be used as is or blended to create another clay, unlike pottery clay; also unlike pottery clay, this type of clay will not stick to your hands.
  • However it cannot be baked in a furnace, or “fired”
  • This clay is commonly marketed for children because it doesn’t stick to your hands and it stays soft and workable and doesn’t harden or dry out over time
  • Popular choice of film studios, fantasy artists, fine artists, film special effects departments, and fantasy comic artists
  • Molds must be made of a finished product and then the molds can be baked; those will hold up better than the original product being baked
  • Needs softening when it comes out of the packet; can be done with your own body heat, in a pan, or in a microwave
  • Much more expensive weight for weight than ceramic modeling clay
  • Different degrees of hardness can be purchased, ranging from hard to medium to soft; can be mixed together for varying consistencies
  • Medium hardness is good for sculpts that are going to have tiny, precise details

Polymer modeling clay

  • Have various degrees of softness at room temperature
  • Can be mixed to combine their individual properties; you can make a softer clay stiffer by combining it with a firmer clay
  • This type of clay when baked should be in an oven at 265—275°F for 15 minutes for each ¼ inch of thickness
  • Once baked, they can be painted although they originally do come in a wide variety of colors and can be mixed
  • Besides the primary colors, they also come in translucent, fluorescent, metallic, and bright varieties
  • Other specialty colors include those with stone-like textures or glow-in-the-dark
  • It can be expensive weight for weight compared to ceramic clay and it’s also weaker than ceramic clay
  • It doesn’t have to baked to be painted

Dough modeling clay

  • Resembles PlayDoh® and is sometimes called playdough
  • Can be edible or inedible
  • Can be easily made at home in both cooked and uncooked versions
  • Less expensive than other types of clay
  • Made of ingredients commonly found in any kitchen: flour, cornstarch, cream of tartar, oil, and water
  • In order to add color, you can just add food coloring before it’s cooked or paint it once it is cooked
  • Most flour-based clays are not meant to be baked and made to last, like gingerbread houses. They tend to crack as they dry. PlayDoh® is meant to be used and reused
  • There are types of air-drying modeling clay, like Activ-Clay® and Model Magic®, that dry better than PlayDoh® and hold up better over time

Pottery or Firing Clay

  • Used for pottery and stoneware
  • Worked by hand and on a potter’s wheel
  • Meant to be air-dried and then fired in a kiln
  • During the firing process, glazes with glossy, matte, or specialty finishes can be used to decorate pottery and are baked on
  • There are glazes for each type, ranging from low fire, mid, and high fire clays
  • Available in terra cotta, a rust-colored clay, and white which tends to look gray when moist but dries white
  • Some clays do have different tints
  • Clays described and categorized by their raw and firing color, texture, throwing amenity, slab, particular uses, and sizes and thicknesses for which they work best

Ceramic clay

  • This type is tricky to work with because it comes out of the bag soft and pliable, and this is when it is best to rough out a basic form
  • But you can only do so much with the clay in this state because it’s too soft to add any details
  • You must allow it to harden before you can proceed
  • Before you begin working on it again, place it on moist plaster
  • If you have to leave the project at any point, be sure to cover it with a clear plastic bag
  • The trick to working with this type of clay is to keep it from drying out but now allowing it to become too moist that it is unworkable
  • Keep a spray bottle of water on hand and spray it every once and awhile when it starts to dry out

Now you know some basic types of modeling clay and their techniques. I even included some tips on working with certain types as a little bonus. Next article, we’ll look at techniques to use when working with clay and other materials.