Shellac

Definition

A natural thermoplastic resin secreted by the female lac bug (Kerria lacca, family Kerriidae), a scale insect native to South and Southeast Asia. The resin forms protective encrustations on twigs and branches as the insect feeds on plant phloem sap; harvested crude lac is processed into refined shellac flakes. Chemically, it comprises aleuritic acid, jalaric acid, shellolic acid, and associated waxes. In entomological and natural-product contexts, shellac exemplifies insect-derived commercial biopolymers used historically and contemporarily in coatings, adhesives, and as a mounting medium for small specimens.

Etymology

From shell + lac, referring to the processed form of lac resin; lac derives from Hindi/Sanskrit lākṣā via Persian and Portuguese trade routes.

Example

Entomologists preparing minute beetles or microlepidoptera for museum collections traditionally brushed dilute shellac onto card points or directly onto specimens to fix delicate appendages and impart structural rigidity; the resin's reversible solubility in ethanol also allowed later remounting.

Synonyms

• lac resin
• refined lac

Related Terms

• lac bug
• scale insect
• cochineal
• Propolis
• insect wax
• mounting medium
• natural resin

Usage Notes

Distinguish shellac from raw sticklac or seedlac (intermediate harvest forms) and from synthetic substitutes. In biological collections, shellac has been largely supplanted by water-soluble adhesives and archival resins, though it persists in specialized applications. The term properly refers to the refined, bleached or dewaxed product; unprocessed lac encrustations contain insect bodies, plant debris, and dye (lac dye, a separate crimson product from the same insect).