Polymer clay can melt — or soften — certain plastics in its raw state. If you place a slab of unbaked polymer clay onto the surface of an incompatible plastic, the plasticizers in the clay can soften the plastic and cause it to unstiffen or "melt."

There are several different plastics made with different materials, and many have the potential to react with polymer clay in different ways. How do you know what plastics are safe to use with polymer clay? Let's talk about which plastics are compatible with polymer clay, which ones are not and how to identify different types of plastic.

What Is Polymer Clay?

Polymer clay is a plastic made of pigments, fillers, lubricants, plasticizers, oils and binders. Known for its versatility and pliability, polymer clay is a man-made, oven-bake modeling material made from a plastic, polyvinyl chloride or PVC base. 

Polymer clay is used by hobbyists and professional clayers alike, ranging from children to movie makers to crafters. It stays soft until baked in a home oven, retaining its size and color. Sculpey® polymer clay is available in several colors, including glow-in-the-dark, granite and metallics. Crafters can use it to simulate many materials such as wood, porcelain, stone and faux stones.

When polymer clay is in an unbaked or raw state, its plasticizers are susceptible to reacting with surrounding materials.

How Does Polymer Clay Melt Plastic? 

One of the ingredients in polymer clay is plasticizers — chemicals that make plastic flexible and soft. After curing your polymer clay creation in the oven, the plasticizers become fused with the clay's PVC particles, making them mostly inert. Uncured clay, on the other hand, has free plasticizers. If you place a piece of raw polymer clay onto a section of incompatible plastic, it can cause it to soften.

What Plastic Is Safe for Polymer Clay? 

Sculpey® recommends storing clay in containers or bags made out of Polypropylene or PP plastic. A box made of PP plastic will have the recycling symbol #5 on the bottom.

Plastics Not Compatible With Polymer Clay 

Plastics not compatible with polymer clay include:

  • PVC polyvinyl chloride — #3
  • PS and EPS polystyrene and expanded polystyrene — #6
  • Other materials that include a combination of different plastics like polycarbonate, Teflon, nylon, acrylics and others — #7

Tips for Storing Sculpey® Clay

It's essential to store any unbaked polymer clay in a compatible plastic container. To err on the side of caution, ensure the tools and work surface in your studio are made from polymer clay-safe materials. Keep Sculpey® stored in containers or bags made of polypropylene plastic and keep it away from painted and wooden furniture, as it can damage some finishes.

Order Sculpey® Clay Online Today 

Get inspired with tools and accessories as well as vibrant color palettes designed for all your polymer clay creations. Order Sculpey® clay today to begin your journey of creative discovery. 

Still have questions about what plastics are safe for polymer clay? Contact us by submitting our general inquiry form.