Technologies in Bamboo Slips

Bamboo slips or bamboo strips (Chinese:简牍) were the most important form of book in ancient China before the invention of paper. Ancient Chinese people chopped bamboo into small slips (Chinese: 简), used knife to smoothen the surface, and baked the slips over fire to kill the hidden insect eggs. Two or three holes were punched on each bamboo slip, and ropes were used to tie the slips through the holes into rolls or pages (Chinese:册).

Bamboo slips had profound impact in the Chinese book history. The terminologies, the writing format, and the Chinese characters all inherited the traditions from the bamboo slips period. The first usage of bamboo slips was found during the Warring States Period (475-211 BC) and lasted until the Northern and Southern dynasties (420-589 AD). Numerous famous ancient Chinese books were able to survive until today due to the inventions of bamboo slips, including The Analects of Confucius, Classic of Poetry, and Book of Documents. The most recent discovery were Tsinghua Bamboo slips, a collection of 2388 bamboo slips donated to Tsinghua University by an alumnus. The most astonishing finding is a decimal multiplication table for multiplying numbers up to 99.5.

The advancement in technology enhanced our knowledge of these bamboo slips in many different ways. This wiki page will briefly discuss in four different parts how new technologies enable archeologists to better study bamboo slips: conservation, authentication, image acquisition, and image post-processing.

Conservation

Conservation is a crucial part of studying bamboo slips. Compared to other historical relics, bamboo slips are usually harder to preserve. Two obstacles archeologists have the encounter during conservation are the structural change and color change of the bamboo slips.

Bamboos, like all other plants, are a collection of cells. Cellular components have carbohydrates, a perfect energy source for insects, bacteria, and fungi. The temperature (25-30 Celsius), pH (4.5-5.5), and water content (35-50%) in the tombs or wells where bamboo slips were found are ideal for the growth of microorganisms. These microorganisms are able to dissolve the cellulose in the cell walls into glucose, thereby destroying the structure of the bamboo cells.

With the assistance of water however, water molecules are able to create hydrogen bonds with the hydroxyl groups in cellulose and support the structure of the cells. This explains why most bamboo slips that have survived until today are the ones soaked in water. Although water helps to preserve the bamboo slips, it also generates a major problem. After the excavation of the bamboo slips, the temperature, pH, and the water content of the environment will dramatically change. If left unattended, water molecules will evaporate from the intervals between celluloses, rendering the bamboo structures weak. Deformation, shrinkage, and ruptures are common problems.

Another risk is the exposure to the oxygen in the air. The iron (2+) ions are able to react with the oxygen to create iron (3+) ions. This chemical change will result in the blackening of the bamboo slips, which makes scholars hard to identify the characters on them.