pH Stability of Saffron Used in Verdigris as an Inhibitor in Persian Miniature Paintings
| Main Authors: | , |
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| Format: | Article |
| Language: | English Slovak |
| Online Access: | http://www.viks.sk/chk/res_3_02_154_164.doc |
| Abstract: | CONLUSIONS. Our results show that saffron can resist a wide range of pH variations. The existence of unsaturated dicarboxylic acid and its esters (crocin, carotenoidesters and crocetin) and nitrogen compounds in the chemical composition of saffron could be responsible for its high resistance. It was shown that the saffron solution, when added to the verdigris pigments acted as a powerful buffering agent, which prevents the charring of paper by maintaining a constant pH. This prevents the destructive mechanism of verdigris by increasing the pH and the local formation of alkaline hydroxide, which is active in the final stage of the degradation process from Fehling reaction. SUMMARIES. Saffron has been identified as having a significant preventive effect on corrosion caused by copper-based green verdigris pigments in Persian and Indian miniature paintings. A scientific examination of the chemical mechanism responsible for the buffering properties of saffron was carried out. The Saffron solution was found to be stronger than common buffers, i.e. more resistant to a wide range of pH in acidic and alkaline media. The chemical mechanism of this phenomenon, based on earlier research by the authors was sought. In addition. Persian medieval texts are discussed where the use of verdigris together with saffron is reported historically. The treatises used were mainly from the Safavid (16th century) and Qajar (19th century) periods. |
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| ISSN: | ISSN 0034-5806 |
