Clay is a material that is often first introduced to children. It lets them discover a new material that flexes and forms in any way they desire. Among adults, clay is used by artists, sculptors and animators for creative purposes. Both polymer clay and modelling clay have their uses in arts and crafts, but they perform very differently. The project should determine whether polymer clay or modelling clay is the better material to use.
Material and Color
Modelling clay is an oil-based compound, while polymer clay is polyvinyl chloride, a plastic-based material. Both materials are available in a wide range of colours, but polymer clay has more options in faux colours, such as granite or translucent shades. Modelling clay has only shades of colour while polymer clay has colours that glitter.
Modelling clay is available in air-dry or no-dry options. Modelling clay is created so that it can be used over and over again so that it never dries out. Polymer clay hardens when it is baked in an oven, though in its unbaked form, it does have a tendency to crumble if left out too long or if it gets too old. There is a special additive sold at craft supply stores, called clay softener, for hardened clay. A few drops of the additive will soften the clay again. Modelling clay stays flexible and pliable.
Animators often use modelling clay because it is reusable. Modelling clay characters are easily moved and rearranged without the worry of breaking their creation. Sculptors use it to visualise ideas while artists use it as a sketching aid. Polymer clay is mainly used for finished projects. Jewellery makers use it for making unique beads in necklaces and earrings, and doll makers apply it to create fairies and figurines.
Because modelling clay is mostly used in non-drying applications, polymer clay is a more durable material for finished projects. It is waterproof when hardened, making it a fitting material to use for buttons, fish tank accents or jewellery. It is also paintable, whereas non-drying modelling clay is not. Air-dry modelling clay is available but is primarily used for children's crafting, so it is not as durable as polymer clay. There are also different types of polymer clay, each one designed for a special use. Read the manufacturer's suggestions about what type to use for your project.