J. Cosmet. Sci., 57, 441-454 (November/December 2006) A facial mask comprising Dead Sea mud BASIM ABU-JDAYIL, Department of Chemical and Petroleum Engineering, United Arab Emirates University, P.O. Box 17555, Al-Ain, UAE, and HAZIM A. MOHAMEED, Department of Chemical Engineering, Jordan University of Science and Technology, P.O. Box 3030, 22110 Irbid,Jordan. Accepted for publication June 27, 2006. Synopsis Many investigators have proved that Dead Sea salt and mud are useful in treating skin disorders and skin diseases. Therefore, the black mud has been extensively used as a base for the preparation of soaps, creams, and unguents for skin care. This study concerns a facial mask made mainly of Dead Sea mud. The effects of temperature and shearing conditions on the rheological behavior of the facial mask were investigated. The mud facial mask exhibited a shear thinning behavior with a yield stress. It was found that the apparent viscosity of the mask has a strong dependence on the shear rate as well as on the temperature. The facial mask exhibited a maximum yield stress and very shear thinning behavior at 40 ° C, which is attributed to the gelatinization of the polysaccharide used to stabilize the mud particles. On the other hand, the mud mask exhibited a time-independent behavior at low temperatures and shear rates and changed to a thixotropic behavior upon increasing both the temperature and the shear rate. The shear thinning and thixotropic behaviors have a significant importance in the ability of the facial mask to spread on the skin: the Dead Sea mud mask can break down for easy spreading, and the applied film can gain viscosity instantaneously to resist running. Moreover, particle sedimentation, which in this case would negatively affect consumer acceptance of the product, occurs slowly due to high viscosity at rest conditions. INTRODUCTION The Dead Sea region is the major spa area in the Middle East for patients with various types of arthritis. The unique climatic conditions in this area and balneologic therapy­ which is based primarily on mud packs and bathing in sulfur baths and in Dead Sea water-combine to alleviate the symptoms of arthritis (1). The Dead Sea has a salt content of about 320 g/1, of which potassium chloride, mag­ nesium chloride, calcium chloride, and sodium chloride (with their respective bromides) are the major components, comprising 98% of the salts on a dry weight basis. Another mineral-rich constituent of the Dead Sea is its "black mud" (rich in organic substances), also known as "bituminous tar." The therapeutic effect of processed Dead Sea mud is Address all correspondence to Basim Abu-Jdayil. 441

442 JOURNAL OF COSMETIC SCIENCE related to its high content of minerals and its ability to retain heat for many hours, thus stimulating blood circulation and clearing the skin of dead epidermal cells (2). It has been shown that Dead Sea salt and mud are useful in treating skin disorders and skin diseases such as psoriasis (3), seborrheic dermatitis, xerosis, attopic dermatitis, stage I skin burns, and sensitive skin (4). In addition, black mud has been extensively used as a base for the preparation of soaps, creams, and unguents for skin care. The manufac­ turers of those products claim that the mud has major effects on revitalizing and toning the skin. Dead Sea mud deep cleanses it removes impurities by deep washing of the skin. It penetrates pores to absorb accumulated dirt, makeup residue, and excess fatty secre­ tions like hardened sebum. The demand for Dead Sea (DS) cosmetics is increasing. Dead Sea cosmetics include shampoos, creams, lotions, masks ... etc. They have Dead Sea salt and/or mud in their formulas. Consumer acceptance of Dead Sea cosmetics depends on the stability of the products and their ability to spread on the skin, which is directly related to flow behavior. Semisolid systems are used widely in the formulation of topical pharmaceutical and cosmetic preparations. Rheological properties of semisolids are highly important physical parameters in technical manufacturing (filling, storage) and in aesthetic terms. The evaluation of semisolid cosmetic structure and consistency is, therefore, essential in order to determine, adjust, and perhaps predict the performance of newly designed products (5). The rheological properties of a semisolid system significantly determine its quality, usefulness, and purpose. Therefore, rheology has always played and will play a role in the preparation, development, and manufacture of any formulation. For that matter, rheological determinations are indispensable in the analysis of its properties. The importance of rheological properties in semisolid pharmaceutical and cosmetic forms is such that rheological and thixotropic studies have become crucial tools from both pharmacotechnical and galenic points of view. In a similar way, rheology can elucidate the possible modifications of the system, expressed as a function of time and tempera­ ture, from the variation in the hysteresis loops of the apparent viscosity (area under the curve) (6). Thus, pharmacotechnical tests that include the determination of organoleptic properties, pH, sign, and macroscopic and microscopic examination allow us to evaluate the evolution of the properties of the formulations mentioned, according to the time, temperature, and gravity. As a rule, the rheological study and, more precisely, the evaluation of thixotropic properties, allow us to obtain a correct picture of the physical properties and structural stability of semisolid systems (7 ,8). This study aimed to use rheological measurements in the evaluation of a commercial facial mask sample made mainly of Dead Sea mud. MATERIALS AND METHODS MATERIALS The facial mask samples were supplied by Ammon for Dead Sea Salts and Soap Products (Amman, Jordan). The components of the mask used were Dead Sea mud (solids) 67 .0 wt%, glycerin 7.0 wt%, and stabilizer (with a trade name of polysaccharide) 1.0-1.5%. The remainder was deionized water. The chemical identity of Dead Sea mud is natural sediment. It is a mixture of solid mineral clays with an interstitial solution of inorganic