Digital Conservation of Cultural Assets - Culture and Computing - page 149

of the temple buildings, are in varying degrees of discoloration, deterioration, pigment
exfoliation and so on, depending on their location, building structure, exposure to the
elements and other factors. For example, all the paintings on the northern side of
Tora-no-ma have blackened, whereas those on the southern side of the same room
retain their original colors. In consideration of this fact, therefore, instead of archiving
each shouhekiga simply as one picture, a multi-scale structure ⎯ as illustrated

Fig.1. has been developed for Nishi Hongwanji Digital Archives, to take into

account the factors affecting the conditions of the respective paintings.

⎯

2.1 Analysis of Pigments

Shouhekiga and ranma are painted with pigments called suihi enogu and iwa enogu .
Suihi enogu is made from mud or earth found mostly in mountains, which is washed
with water to remove impurities and then dried in plate form. Iwa enogu , granular
pigments made of various crushed minerals and semi-precious stones, are used with
nikawa (glue) as a binder. They come in only a few basic colors, but this single raw
material can yield a variety of hues, depending on the granule diameter. This
characteristic is used to achieve various nuances and a three-dimensional effect.
Granule diameters are indicated by numbers: the higher the number, the finer the
granule. The finest granule is called byaku (see Fig.2. and Table 1).

Fig. 2. Iwa enogu numbers and gradations

Table 1. Table 1 Iwa enogu numbers and granule diameters

Number 6 7 8 9 10 11 12 13

Av.
diam(μm) 120 100 70 50 30 15 10 7

• X-ray fluorescence (XRF) analysis

• Granular diameters

• Reflection spectra

The results of these measurements revealed that the pigment rokusho (green) No. 8 is
used in the bamboo sections of well-preserved shouhekiga . At the same time, the
results led to the assumption that the same pigment is used in the bamboo sections of
deteriorated paintings and that the pigment oudo (yellow ocher) is used in the tiger
sections.