The samples were removed from the plaster with

The samples were removed from the plaster with pointed-tip- tweezers and placed on a glass slide.
Under the microscope, Type A fibres are in a bundle, while Type B fibres are plant stem. The fibres
were soaked in a drop of deionized water to let them relax. Extra plaster residue was removed as
much as possible at the same time. Then the sample was covered with a glass lid and the fibres were
dispersed with pressure for direct observation.
Type A fibres are fine and light yellow in color. Tapering and pointed or rounded cell end can be seen.
The ends are more narrow than the central part. The width of the fibre varies. The lumen is not always
apparent. If the lumen shows up, it is thin and discontinuous. The transverse dislocations are apparent.
There are no bifurcated ends have been observation in Type A . According to Catling (1982:10), jute
and ramie are two common species planted and produced in southeast China. Therefore, based on
above characteristics of longitudinal section, fibre Type A is likely ramie.
Type B fibres are part of original stem. The stem is in yellowish golden colour. Fibres (blue) can be
seen in between of the longitudinal section of the stem. Rhombic crystals (Petraco, 2004:107) were
also found. After mashing the stem, fiber cells with scalloped edges were separated and observed.
According to those characteristics (Catling, 1982:39), Type B fibers are likely jute stem.

Pun Uk Mansion – Preliminary Investigation of Architectural Finishes – Architectural Conservation Laboratory HKU Faculty of Architecture - July 2018
Appendix 7
Likely, there is less chance to use two types of fibers during one application of plaster. However, it is
not saying that it is impossible. Additionally, refurbishment over time may cause differential of using
materials. Therefore, more comprehensive conclusion may be drawn combined with other scientific
results.
In consultation with a local historic building restorer, it was discovered that “straw” 禾草 is commonly
used as a reinforcement material in plaster for the restoration of historic buildings. A straw sample
from a local source was treated before observation. Dried straw samples were soaked in water
overnight and mashed into small fibres in the second day. Microscopic observation process is the
same as Pun Uk samples. The result shows that straw fibre has distinctive characteristics from the
sample from Pun Uk. Therefore, the Pun Uk fibres are not likely the “straw”.
In the studies of historic buildings, fibre （ 麻 / 披麻） has been commonly prescribed in the substrate
layers ( 王时伟 , et.al 2013:115-117; 曹春平 , 2006:45) to strengthen the finish. However, no specific
species was given by the authors, and the applications of fibres are different compared with what we
see in our sample.
Literature
1. 王时伟 ., 吴生茂 ., 杨红 ., 赵鹏 ., 郭泓 ., 吴生茂 , . . . 郭泓 . (2013). 清代官式建筑营造技艺 (Di 1
ban.; 第 1 版 . ed., 中国传统建筑营造技艺丛书 ), pp.115-117.