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This study reveals the characteristics and deteriorations of the stones and mortars of Rumelifeneri Fortress within detailed field studies and laboratory analyses. Visual observations on the site indicate that the northeastern façade represents nearly all of the deteriorations. Thus, a mapping of the façade was prepared to obtain complete identification of geology of the area and all deteriorations based on the architectural survey and rectified photographs (Figure 3).

The geological formation of the area is called “Garipçe Formation” which is from Upper Cretaceous and Lower Eocene era. The fortress is located on the lava of Rumelifeneri which consists of andesite and basaltic andesite. The location has two layers of lava, the later phase lava is grey and black colored while the earlier phase lava is reddish and dark brownish. (Yavuz and Yılmaz 2010). Thus, these two different basaltic andesite lavas were identified as Lava 1 (reddish colored) and Lava 2 (grey colored). ICOMOS – ISCS Illustrated Glossary on Stone Deterioration Patterns was used for defining the deterioration types (ICOMOS 2008) and different levels of stone deteriorations (differential erosion, alveolization and coving) were shown with different shades of the same color for each stone type. Besides, discolouration (black), calcite encrustation, salt crust, lichens and graffiti were also observed on the façade and indicated on the mapping. In addition, all of the deterioration types were gathered together on a table to create a deterioration glossary for the building (Figure 4).

Figure 3: Mapping of deteriorations on northeastern façade, April 2019.

Figure 4: Deterioration types encountered on Rumelifeneri Fortress.

Laboratory studies were carried out for characterization of the materials used on the building. Within this context 13 samples (10 mortar and 3 stone) 49were taken from both sound and deteriorated parts of the building. Locations of the samples were indicated on the scaled drawings (Figure 2, 3). The details about the samples can be seen in Table 1. The sampling was followed by laboratory analysis. Chemical and physical analyses were conducted on the samples to determine the characteristics of the original materials and the causes and the depth of deterioration. Acid loss test, sieve analysis, ignition loss test, protein and oil spot tests were performed on mortars. The water soluble salt content of the mortars was also analyzed. (Pekmezci and Ersen 2010; Güleç and Ersen 1998; Middendorf et al. 2005; Teutonico 1988; KUDEB 2011). The stone samples were examined by using SEM-EDS.

Table 1: Description of the samples.

Sample No	Description
M1	Masonry mortar with yellowish colored binder, stone and seashell aggregate under 5mm
M2	Masonry mortar with white colored binder, sand and seashell aggregate under 3mm
M3	Masonry mortar with yellowish colored binder, stone aggregate under 8mm
M4	Masonry mortar with white colored binder, stone and seashell aggregate under 5mm
M5	Strong masonry mortar with white colored binder, stone & seashell aggregate under 8mm
M6	Strong joint mortar with white colored binder, stone & seashell aggregate under 2mm
M7	Masonry mortar with white colored binder, stone and seashell aggregate under 6mm
M8	Strong mortar with yellowish colored binder, stone & seashell agg. under 4mm
M9	Plaster with pinkish colored binder and brick aggregate under 4mm
M10	Strong masonry mortar with yellowish colored binder, stone aggregate under 1mm
S1	Gray colored basaltic andesite lava, discolouration (black)
S2	Greenish colored basaltic andesitic breccia, lichens
S3	Dark brownish-reddish colored basaltic andesite lava, coving