Architectural Conservation Laboratory HKU Faculty of Architecture - July 2018 4 2Regular Plaster Finish Most of the structural brick at the exterior and interior of the mansion are covered with a smooth, whitish plaster finish. For this report, this undecorated plaster is termed “regular plaster.” The plaster finish extends from the floor to the ceilings. The timber ceilings are not covered with plaster finish; instead they are painted a solid colour or enhanced with wood grain imitation painting (further details provided in Section 5.2 Wood Graining). The plaster was applied in two layers: a thicker, rougher inner layer (referred to as Layer 1 and abbreviated as L1) and an outer, thinner layer with a much smoother surface (Layer 2 or L2). Visible scratches or scoring lines are evident in the L1 layer (noted in Figure 1), likely to improve adhesion of L2 to L1. The texture of the outer layer, L2, appeared to vary throughout the structure, from a solid, fine-grained coat (as seen in Figure 2) to a slightly rougher texture (not shown). The condition of the plaster ranged from intact, seemingly well adhered sections with mild discoloration to regions stained green to black from algae and mildew growth along with water intrusion as seen in Figure 3. The outer layer of plaster had also completely separated from the inner layer of plaster in some areas, especially notable in the archway leading from the Central Courtyard to Service 3 (area marked in Figure ). Roof distress and a large wall crack was noted in this region, and the plaster delamination could be due to water intrusion from the compromised roof, possible foundation movement or both. The finish was also entirely missing with the structural brick exposed at several exterior locations, including the west wall and around the door frame on the north side of the structure (see Figure 4 and Figure 5). Figure 1. Missing portions of L2 at the archway between the Central Courtyard and Service 3 revealing the rough, possibly scored texture of L1. Figure 2. Fine finish of the outer layer of plaster. Exposed plaster is darker compared to the plaster behind theelectrical box, indicating an overall darkening of the plaster.
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Pun Uk Mansion –Preliminary Investigation of Architectural Finishes –Architectural Conservation Laboratory HKU Faculty of Architecture - July 2018 5 Figure 3. Discoloration due to mildew/algae growth. Also missing plaster revealing L1 and L2 plaster layers. Rising damp likely promoted ideal conditions for plant growth. “Ink” drawing on plaster visible through growth (discussed in Section 3.1.1 Monochrome painted plaster samples).Figure 4.Exposed structural brick due to missing plaster on north end of west exterior wall. Figure 5.Missing plaster from the north exterior wall by thedoor leading to Side Hall 1, revealing apparent concrete frame around door opening that may be original or a possible later repair. Structural brick and the inner (L1) and outer (L2) layers of plaster are also visible.