Overview
Sindoordaan refers to the ritual application of sindoor (Hindi: सिंदूर; Sanskrit: सिन्दूर, IAST: sindūra), a traditional vermilion, orange-red or maroon cosmetic powder used in South Asia. Within Hindu wedding customs, sindoor is applied along the parting of a woman's hairline, marking an important moment in the marriage ceremony.
In Hindu communities, sindoor is regarded as auspicious and serves as a visual marker of a woman's marital status. The practice of wearing it is associated with married life, and ceasing to wear sindoor is customarily understood to signify widowhood.
Traditional sindoor was prepared using natural ingredients such as turmeric combined with alum or lime, or other herbal substances. These traditional preparations, unlike formulations based on red lead or vermilion, are not poisonous. Some commercially available sindoor products, however, are made with synthetic ingredients, and certain products that are not manufactured to proper standards may contain lead.
References
Adapted from the English Wikipedia article on Sindoor.