You can freely build on How Play-Doh Was Invented
This patent expired in 1982. Every claim — 1 independent, 0 dependent — is now unenforceable. Anyone can use, reproduce, manufacture, sell, or offer for sale this technology without a license.
Original assignee
Rainbow Crafts Inc
Patent granted
1965
Expired
1982
Forward citations
29
What this patent covers
The patent defines a specific chemical mixture that creates a soft, pliable, and non-sticky modeling clay. The composition relies on a precise ratio of grain flour, water, a water-soluble inorganic chlorine salt, and a small amount of kerosene. This combination allows the material to remain lump-free and re-workable over long periods without drying out or becoming toxic to children. By balancing these ingredients, the inventors created a substance that holds its shape when molded but remains soft enough for easy manipulation.
What is now free to use
All 1 claims of US 3167440 are in the public domain. Specifically:
Claim 1: A SMOOTH AND VELVETY COMPOSITION OF MATTER WHICH IS SOFT, PLIABLE, NON-STICKY, NON-TOXIC SUBSTANTIALLY LUMPFREE, RE-WORKABLE AND RE-MOLDABLE — 1 specific element
The 0 dependent claims add narrowing limitations and are also free.
What is NOT covered
Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.
Does not cover modeling compounds that exclude the specific range of kerosene as a lubricant.
Does not cover clay-based modeling materials that do not use grain flour as the primary base.
Does not cover mixtures that omit the water-soluble inorganic chlorine salt.
Who is building on this today
Hasbro, which acquired the Play-Doh brand, continues to manufacture and iterate on the product line. Many competitors in the modeling clay market have since developed non-toxic, flour-based alternatives that iterate on the basic principles of this original formula.
Products built on expired version of this technology
Play-Doh modeling compound
How to cite this patent in your documentation
Rainbow Crafts Inc. US Patent 3167440. Plastic modeling composition of a soft, pliable working consistency. Granted 1965, expired 1982. Now in the public domain.
Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.
PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.