Whimsical tea light candleholder is ornately decorated. The terra cotta color wash, called kosh is made from catechu and mangosteen extract. Catechu is an astringent water-soluble substance extracted from the Asian acacia tree. It is used in medicine, in dyeing and in betel-leaf. Mangosteen is a tropical edible fruit. In Bangladesh, any sort of botanical extract is known as kosh.