How Does Mother-of-Pearl in Najeon Lacquerware Become Iridescent?

Shell Inlay, So Why Does the Color Move?

The shell inlay of a najeon chilgi (螺鈿漆器, mother-of-pearl lacquerware) box or table can shift between blue, red, and green as the viewing angle changes. Understanding this iridescence calls for a look at the fine layers inside the material. Explaining iridescence through structure is different from saying that nacre contains no pigments. Research on yellow Akoya pearl-oyster nacre also examines coloration associated with its chemical constituents.

The Handiwork of Cutting and Inlaying Shell

Najeon chilgi is a traditional Korean craft in which ‘jagae’ — thin slices of abalone or turban shell — are attached to a wooden base and finished with lacquer; it was also called ‘jagaebagi’ in native Korean. The craft’s origins trace back to shell-inlay artifacts excavated from 6th-century Silla tombs, and it reached its peak during the Goryeo dynasty, establishing a distinctive style; the Joseon dynasty carried the craft on as a specialized skill through a government office of najeonjang (螺鈿匠, mother-of-pearl artisans). This craftsmanship was designated a National Intangible Heritage (National Intangible Cultural Heritage No. 10) in 1966.

There are two core techniques. ‘Kkeuneumjil’ uses a cutting knife to slice shell into thin strips joined together to form geometric patterns, while ‘jureumjil’ cuts shapes from a design to depict pictorial motifs such as plum blossoms or chrysanthemums. Both use shell pieces trimmed to about 0.5–1 millimeter thick. Only around 20 Goryeo-era najeon lacquerware pieces survive intact worldwide, renowned for their refinement. Of the three held by the National Museum of Korea, the ‘Najeon Sutra Box’ was designated Treasure No. 1975 in 2018, and the ‘Mother-of-Pearl Box with Chrysanthemum Scroll Design,’ repatriated in 2020, bears roughly 45,000 individual shell pieces.

Nacre: A Material Built from Fine Layers

Mother-of-pearl inlay uses nacre from the inside of mollusk shells. Thin aragonite plates, made of calcium carbonate, occur together with organic layers containing proteins, chitin, and other components. This is often compared to bricks and mortar. Dimensions and arrangements vary among samples. Research linking nacre color with structure examines aragonite layers hundreds of nanometers thick. The diagram below simplifies this layered arrangement.

Interfaces between plates and organic material affect deformation and the path of cracks. A 2020 study of nacre also examined how groups of plates deform together and store energy. Structures at several scales contribute to its behavior. Energy required for fracture and strength are different quantities, so nacre should not be described as thousands of times stronger under every condition.

The Color That Light Makes on Impact: Structural Color

Light transmitted and reflected through nacre’s thin layers overlaps, reinforcing some wavelengths and weakening others. Color produced through this interference is structural color. Research on layer thickness and interference color used iridescent patterns to investigate nacre structure. The diagram below shows a basic interference relationship, while real nacre contains many layers as well as surface structure.

Changing the illumination or viewing direction can change interference conditions and the reflected color. Structural coloration does not remove the effects of light absorption by the material’s constituents. Distinguishing these contributions gives a more accurate account of nacre’s appearance. Najeon lacquerware turns this material into patterns through the cutting and inlaying techniques of kkeuneumjil and jureumjil.

Why Materials Science Is Paying Attention Again

Nacre provides a model for combining hard plates with organic layers. Examining both its reflected colors and its response to cracks reminds us to distinguish different material properties. The shell pieces cut and inlaid by an artisan embody both skilled handiwork and the interaction between light and fine structure. Learning about that interaction offers another way to see the intricacy of creation.

Correction · 2026-09-21 We revised the claim that nacre contains no pigment and distinguished structural color from coloration associated with its constituents. We removed a broad multiplier that conflated material properties and linked the discussion of cracks and deformation to original research.

References

• Najeon chilgi (Mother-of-pearl lacquerware) – Korean Wikipedia
• Najeon Sutra Box – Korean Wikipedia
• Najeon chilgi – Encyclopedia of Korean Culture
• Kkeuneumjil – Encyclopedia of Korean Culture
• Najeonjang (Mother-of-pearl Artisan) – Encyclopedia of Korean Culture
• Devotion Held in Shell: Najeonjang – Korea Heritage Service, Monthly Heritage Love
• Najeon Sutra Box | National Treasures and Treasures Search – National Museum of Korea
• 800 Years of Goryeo Light Has Returned
• Nacre – Wikipedia
• Structural coloration – Wikipedia
• Investigation of nacre nanostructure by analyzing its structural color pattern — Scientific Reports (2021)
• Nacre toughening due to cooperative plastic deformation of stacks of co-oriented aragonite platelets — Communications Materials (2020)
• Trivalent Iron Is Responsible for the Yellow Color Development in the Nacre of Akoya Pearl Oyster Shells — Marine Biotechnology (2020)