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Abstract: (874 Views)
Ali Qoli Agha bathhouse was built in the Safavid period and was decorated with glazed haft-rang tiles. The architectural revetments underwent some interventions during the Qajar period so that wall paintings were added and new haft rang tiles adorned the interior decoration of the building. The haft rang tiles bear floral and animal patterns together with geometric designs. In the first glance, a severe damage can be evinced within the tiles. While the Safavid tiles suffer from detachment of the low lead alkali white glaze layer, the Qajar tiles are severely faded so that patterns cannot be observed readily and the designs may not be tracked easily with naked eyes. We show that a significant difference between the thermal expansion of the Safavid lead alkali glaze and that of the calcareous clay body is the main reason for the detachment of the Safavid glazes from their body. Also, the Qajar glazed tiles are mainly faded due to the alkali leaching and, in addition, the undissolved quartz crystals and bubbly glazes have imposed to the glazes. Our field observations furthermore show that the crystallization of soluble salts in the monument is on significant importance in the deterioration of the glazed tiles. Based on scanning electron microscopy – energy dispersive spectrometry (SEM-EDS), micro-Raman spectroscopy and chemical wet tests, we show that calcium sulphate dihydrate, sodium and potassium nitrates and sodium chloride are the main salts attacking the glazed tiles. In fact, soluble chloride, sulphate and nitrate salts in the building accelerate the deterioration process of the tiles by crystallization and dissolution cycles which occur within the equilibrium relative humidity (EQRH) of the salts. We demonstrate that these salts are originated from past and current activities in or around the bathhouse. Based on field observations and analysis of thermal camera data, we show that ascending, descending and condensed humidity caused by precipitation, local activities in the vicinity of Ali Qoli Agha bath and activities within the Ali Qali Agha bath are the main reasons for the destruction of haft rang Safavid and Qajar tiles. This research shows that the combined effect of the cycles of crystallization, dissolution and recrystallization of soluble salts along with temperature and humidity fluctuations have weakened the adherence of the glaze to the body of the tiles from Ali Qali Agha bathhouse and has caused considerable damage.
Article number: 127
Type of Study: Case-study |
Subject:
Maremat
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