Journal of Ceramic Processing Research. Vol. 15, No. 6, pp. 393~397 (2014) 393 J O U R N A L O F Ceramic Processing Research Investigation of porosity of ceramic tiles by means of image analysis method Zahide Bayer Ozturk a, * and Nuran Ay b a Department of Metallurgical and Materials Engineering, Nevsehir Hacι Bektas Veli University, Nevsehir, Turkey b Department of Materials Science Engineering, Anadolu University, Eskisehir, Turkey Amount, size and distribution of porosity are among the important factors which affect physical and mechanical properties of ceramic tiles. In this study, the effect of flux variation in porcelain tile recipes and different firing conditions were investigated. X-ray diffraction and Rietveld analyses were used to determine how fluxes affect the phases of samples. In the consequence of these analyses it was found that changing the variation of fluxes and different firing conditions increased liquid phase amount and densification hence the amount and size distribution of porosity decreased. Image analysis method was used to determine the amount and morphology of porosity of porcelain tiles and the results were compared with Archimedes method, Helium pycnometer. Parallel between the amount of porosity determined through image analysis and the amount determined through Archimedes test and helium pycnometer and the possibility of determining the size distribution and morphology of porosity showed that this new method is advantageous. Key words: Image analysis, Porcelain tile, Porosity. Introduction Porcelain tile has increasingly become a widely-used ceramic product in recent years. According to ISO 10545, various features of porcelain tile such as high amount of abrasion resistance (< 205 mm 3 ), the low water absorption value (< 0.5%), high bending strength (> 27 N/mm 2 ), resistance to frost and chemicals gained it a significant place in the sector [1]. The relationship between mechanical strength, stain resistance of ceramic materials and the size of porosity, and volume has been the subject of various studies. Amoros et al. [2] studied the amount of porosity of porcelain tile samples in different grinding conditions after sintering and they determined that insufficient grinding conditions formed large porosity in the body after sintering; therefore stain resistance was adversely affected. Dondi et al. [3] indicated that the most important variables affecting the stain resistance are size and amount of porosity in porcelain tile microstructure after polishing. Kobayashi et al. [4] investigated the effect of different firing temperatures on bending strength of the porcelain. In their study, they showed that spherical and small-size porosity in microstructure had a positive impact on the strength and an increment in the amount of porosity decreased strength exponentially. The porosity is connected to the liquid phase during firing [5] and is affected by the transformations that occur during sintering. For this reason, selection of components and fluxes that affect the microstructure phases and alkaline amounts are important [6]. The microstructure of ceramic materials is composed of crystals, liquid phase and porosity. Fluxing raw materials in recipes decrease the temperature of the liquid phase formation and the viscosity of the glassy phase [7-12]. The fluxing components used as auxiliary components to facilitate the sintering of ceramic product and the formation of liquid phase is potassium feldspar, sodium feldspar and calcium feldspar. Other fluxing raw materials are nepheline syenite, dolomite, wollastonite and talc [13-15]. When talc is added to body even in small percentages (2-5%), it contributes to production of dense ceramic products with low water absorption (porcelain tiles) producing low- melting- point eutectic mixtures via alkaline feldspars [16]. Sintering a material leads to formation of closed porosity and open porosity which is connected to the surface. Mass density of bodies and open porosity are determined through Archimedes method in accordance with Eq. (1) and Eq. (2). According to this method, the density is calculated based on dry weights of fired samples (W d ), weights in water after 4 hours of boiling (W w ) and wet weights after cleaning the surface (W s ). Bulk density (1) Open porosity (%) (2) A certain amount of helium gas is sent from a reference volume to the cell including the sample and the gas is forced enter from one side and exit from the w d w w w – ------------- s w w w d – w w w s – --------------- 100 × *Corresponding author: Tel : +90-384-228-10-00/15050 Fax: +90-384-228-10-37 E-mail: z.ozturk@nevsehir.edu.tr