The Study and Experiment on Embedding Low-Quality Black Sapphire into Ceramic as an Alternative Material in Jewelry

Abstract

This research aimed to 1) study and experiment on embedding low-quality gemstones into two types of clay (high-quality porcelain clay (PFA) and vitreous china clay (VCB)) and 2) compare the suitability between porcelain clay and vitreous china clay for making ceramic jewelry. The size of low-quality black sapphire in diameter were 1.5, 2.0, 2.5, and 3 mm. The low-quality of black sapphires were embedding via the flush setting method with 3 black sapphires for 1 sample and the distance of each black sapphire were 0, 0.7, and 1.4 mm. Each condition was repeated for 3 samples. The total samples for a type of clay were 36 samples. The clay with black sapphire samples was sintering at 1250 °C. The criteria for analyzing the quality of the samples after firing included two points. The first consisted of the qualities of the gemstone after heating comprising of the colors of gemstone, cracks in gems and agglutination with ceramic body. The second point composed of qualities of ceramic including the colors of ceramic and cracks in ceramic. Both the colors and cracks of gemstone and ceramic were analyzed by describing the samples appearances and taking pictures with high magnification camera. It was found that the low-quality black sapphires could be embedded onto two types of clay. The gemstones were shown  as the same color as before and after sintering and no more cracked gemstones. The color of porcelain clay after sintering presented brownish white. All sizes of gemstone could be embedded in the porcelain clay and the best size of the gemstone was 1.5 mm in diameter. It was also found that all the distances of each gemstone presented not cracked in ceramic and gemstone and not be squeeze and pulled out. The porcelain clay showed the 10 unqualified samples. The vitreous china clay after sintering presented cool white color and 16 unqualified samples.