Science, Tech, Math › Science Does Polymer Clay Go Bad? Find out if polymer clay goes bad and how to renew it Share Flipboard Email Print Dorling Kindersley, Getty Images Science Chemistry Chemistry In Everyday Life Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated February 05, 2018 If it is stored correctly, polymer clay lasts indefinitely (a decade or longer). However, it can dry out and it's possible to ruin it under certain conditions. Before talking about how to tell whether your clay is beyond help and how you may be able to save it, it's helpful to know what polymer clay is. What Is Polymer Clay Made Of? Polymer clay is a type of man-made "clay" that is popular for making jewelry, models, and other crafts. There are many brands of polymer clay, such as Fimo, Sculpey, Kato, and Cernit, but all brands are PVC or polyvinyl chloride resin in a phthalate plasticizer base. The clay does not dry out in the air but requires heat to set it. How Polymer Clay Goes Bad Unopened polymer clay won't go bad if it is stored in a cool location. The same is true for opened packages of polymer clay that are stored in sealed plastic containers. However, if the clay spends significant time in a hot place (around 100 F) for an extended length of time, it will cure. If the clay hardens, there's nothing to be done. You can't fix the problem, but you can prevent it. Keep your clay out of the attic or garage or anywhere it could get cooked! As it ages, it's natural for the liquid medium to leach out of polymer clay. If the container is sealed, you can work the clay to soften it back up. If the package had any sort of hole, the liquid may have escaped. This clay may be dry and crumbly and too hard to work. But, if it's not hardened from heat, it's easy to renew the dried out clay. How to Fix Dried out Polymer Clay All you need to do is work a few drops of mineral oil into the clay. Pure mineral oil is best, but baby oil works fine, too. Although I have not tried it, lecithin also is reported to revive dried polymer clay. Working the oil into the clay may take some time and muscle. You can put the clay and oil in a container for a few hours to give the oil time to penetrate. Condition the polymer clay as you would fresh clay. If you get too much oil and want to stiffen the polymer clay, use cardboard or paper to absorb excess oil. This tip works for fresh polymer clay, too. Either allow the clay to rest in a paper bag or sandwiched between two pieces of cardboard. The paper will wick away the oil.