Science: Shellac Substitute

Shellac has been a critical material ever since the war cut supplies from India, virtually its sole producer. Shellac has unique properties as a protective finish, and none of its many substitutes has been quite satisfactory. But last week a new product was announced that seems to solve the shellac problem. It is called Zinlac and can be made cheaply from U.S. corn.

Natural shellac is produced in much the same way as beeswax. It is a resin secreted by insects called Laccifer lacca. After feeding on the sap of certain cultivated Oriental trees, the insects coat the tree twigs with an exudation called “lac” (from the Sanskrit word laksha, meaning 100,000, referring to the thousands of insects in a colony). Indian natives scrape the lac off the twigs, heat it in cloth bags, strain off the melted shellac. The final product is a flaky substance that dissolves readily in alcohol and, when spread on a surface, dries quickly to a hard, tough coat.

No one has ever duplicated shellac’s complicated chemical structure. But Chem ist C. G. Harford, of the Arthur D. Little laboratory in Cambridge, Mass., found that a resin named zein, derived from corn, behaved very much like shellac. A drawback, however, was that in solution zein had a tendency to jell. By an un disclosed chemical process, Harford finally succeeded in converting zein into a non-jelling resin. The result, Zinlac, not only has the quick-drying, elastic qualities of shellac, but is also more resistant to water and makes a better coat for metal.

Restricted to war uses, Zinlac is used by the Army, Navy and Merchant Marine as coating for a great variety of equipment, from guns to life rafts. Its manufacturer, the old Manhattan shellac firm of William Zinsser & Co., is turning out more Zinlac than its total prewar sales of shellac. Zin lac, however, will not help in making phonograph records, normally one of the chief U.S. users of shellac. On records, this corn product does not work.