Multispectral System Tracks Condition of 2,000-Year-Old Wooden Slips

Dragon Media News Desk

The Gansu Jiandu Museum in China is using a multispectral imaging system to recover faded writing and monitor the condition of ancient bamboo and wooden slips. The system captures images across 32 spectral bands, from near-ultraviolet to near-infrared light.

Most of the slips were unearthed at ancient frontier fortresses and date back to the Han Dynasty, making them about 2,000 years old. Made mainly from poplar, rose willow and pine, they have deteriorated after centuries in the arid Gobi environment. The damage includes salt deposits, insect damage, mildew stains and cracks, all of which complicate the interpretation and study of their texts.

Dorje Rinchen of the museum’s conservation department said infrared imaging can reveal ink marks that are difficult to see on the bamboo and wooden surfaces. Ultraviolet images can also show fine cracks and salt deposits invisible to the naked eye. Because imaging in a single wavelength band captures only part of the information, the museum began using the multispectral system in 2025.

By comparing how different wavelengths interact with ink, stains and damaged areas, the system can reveal faded writing, distinguish original ink from later contamination, and identify the location and extent of deterioration. More than 500 slips have been documented, with 33 images—including an original image—created for each one.

Rinchen said the slips are non-renewable organic cultural relics that gradually deteriorate under natural conditions. The museum has created detailed condition records for them and can take and compare new images over time to monitor changes.

Du Peng, deputy general manager of Tianjin Hengda Wenbo Technology, which developed the system, said the technology could also be used to document calligraphy, paintings, artifacts, cave murals and tomb murals, as well as to identify hidden information and support virtual restoration.