Preparation of Lake Pigment from Thai Lac Dye Eakkaluk Wongwad, Ampa Jimtaisong + , Nisakorn Saewan and Panvipa Krisadaphong School of Cosmetic Science, Mae Fah Luang University, Chiang Rai, Thailand, 57100 Abstract. Lac natural dye is a red color product obtained from female insect Coccus laccae (Laccifer lacca Kerr). In Thailand, lac dye is used as a natural red dyestuff for cotton and silk dyeing. Mordants, which is usually different metal salts, can form complexes with the dye molecules via coordinate bonds. These complexes are insoluble and hence improve the dye fastness. Therefore, preparation of lake pigment from Thai lac dye using four metal salts AlK(SO 4 ) 2 .12H 2 O, AlCl 3 , CaCO 3 , and Ca[CH 3 COO] 2 .H 2 O was investigated. The lac lake was prepared at different conditions such as pH, temperature, reaction time and metal salt concentration. The suitable condition for the lake preparation is of pH 3.5±0.1 at 100 °C, 2h and suitable metal salt is AlK(SO 4 ) 2 .12H 2 O and Ca[CH 3 COO] 2 .H 2 O. The UV-Vis spectra of lac lake complex showed the bathochromic shift from that of lac dye which may due to a result of coordination by lone pair electrons on the N or O donor atoms with metal ions, thus stabilizing the excited state relative to the ground state leading to longer wavelength absorption maxima and this potential coordinating between metal salt and lac dye is also illustrated in FT-IR analysis. The structure of lac dye was changed after reacted with metal salts and there is new crystalline peaks formed in XRD analysis. Keywords: Lac natural dye, Laccaic acid, Lake pigment, Metal salt 1. Introduction Lac natural dye is a red color obtained from female insects Coccus laccae (Laccifer lacca Kerr). Water extraction of stick-lac produces the lac dye at about 0.5-0.75% by weight of stick lac [1]. Lac dye is a mixture of at least five closely related laccaic acids derived from 2-phenlantraquinone. These five acids are Laccaic acid A, B, C, D and E, but the main major acids are Laccaic acid A and B (Laccaic acid A 71-96%; Laccaic acid B 0-20%) [2]. Laccaic acids are water soluble red dye of antraquinoid type structure. In Thailand, lac dye is used as a natural red dyestuff for cotton and silk dyeing [3]. Mordants can form complexes with the dye molecules via coordinate bonds, and different metal salts can be used as mordants in the process (e.g. potassium dicomate, tin chloride, and copper sulfate). These complexes are insoluble and hence improve the staining ability of a dye as well as increase its fastness [4]. Therefore, the water soluble dye can be converted into an insoluble pigment by making it into a lake. Carmine is red pigment used in foods and cosmetics and it is an example of lake pigment produced by reaction of natural cochineal (carminic acid) and aluminium salt. Carminic acid is an antraquinone type dye with a bright red shade, and is the most resistance to light-induce-fading [5]. Thus, it is of interest to study the preparation of laccaic acid lake pigment which has not been extensively studied before. Therefore, the purpose of this work was to study the reaction of Thai lac dye and metal salts at different conditions such as pH, temperature, and reaction time. The properties of the resulting lake will be studied using various spectroscopy methods. 2. Experimental Procedure 2.1. Chemicals and Reagents + Corresponding author. Tel.: +66 53916843; fax: +66 5391 6831 E-mail address: ampa@mfu.ac.th 73 2012 2nd International Conference on Biomedical Engineering and Technology IPCBEE vol. 34 (2012) © (2012) IACSIT Press, Singapore