Several types of modeling clay are available for various uses. You can make modeling clay for children with a few simple ingredients; commercially made, nontoxic children's modeling clay is also available. When you need modeling clay that you can harden in an oven or kiln for more permanent uses, manufactured products containing different types of materials will meet your artistic needs.
Flour, Water and Salt
The simplest recipe for modeling clay, long a favorite of parents with young children, contains 3 parts flour, 1 part water and 1 part salt. No cooking is required; you simply mix up the ingredients in a bowl, and the clay is ready for your child's artistic play. Although this concoction does not taste good, you need not worry about your little one trying a bite, since it is nontoxic. You can even mix a few drops of food coloring into the clay for added interest. The clay will harden if left out, but do not attempt to bake it.
Cornstarch, Baking Soda and Water
A quick-cook modeling clay that is both child-friendly and a favorite of crafters contains 1 cup cornstarch, 2 cups baking soda and 1 1/4 cups water. Food coloring is your choice. Combine your ingredients, and cook over medium heat for five minutes or until the mixture thickens to an oatmeal consistency. You and your children can create your masterpieces and then let them air-dry overnight. (Note that these are toddler-safe ingredients.)
Sand, Cornstarch and Water
The ingredients in sand clay are 2 parts fine sand, 1 part cornstarch and 1 part water. Heat the water to boiling, and add it to the dry ingredients; cook the concoction for several minutes until it starts to thicken. When cool, this modeling clay is ready to go. Once your artistic talents are spent, lay your products flat on a cookie sheet and bake at 275 degrees until dry.
Although many of the ingredients in commercially made polymer clay are company secrets, the primary ingredient in such art store modeling clay as Sculpey and Fimo is polyvinyl chloride, the stuff PVC pipe is made of. Softening chemicals known as phthalates provide the malleability that allows you to mold items in fine detail. Once your products are complete, bake the polymer clay in a warm oven until hardened. Polyvinyl chloride and phthalates are highly toxic, especially their baking fumes, which contain dioxin. According to a study by the Vermont Public Interest Research Group, a total of 11 to 14 percent of the contents of Fimo modeling clay consists of phthalates, and around 4 percent of Sculpey is phthalates. The health risks of phthalates as reported by the Vermont Public Interest Research Group include birth defects, reproductive disorders, liver disorders and cancer.
Pottery artisans use natural clay and water for forming and then firing products in a kiln--a specially made oven for drying clay and brick. Once the items are fired, the artists will paint them, apply glaze and refire as needed for beauty and durability.