Question: Is my Wodhu and Salah valid after putting mehdi on finger nails?

Answer: Yes your wodhu and Salah will be valid after putting mehdi on finger nails, because it is not glossy or enamel substance or object. On the other hand, putting nail polish or varnish will invalidate wodhu and Salah due to its substance being lacquer and polymer which are kind of glossy or enamel components that gives a unique colour to it.

Eventually with nail polish when washing hands the water does not pass through the finger nails or toenails. Moreover, putting mehdi on hands or feet are only allowed for women and not permissible for men to put on hands.

References: [1] Fatwa Alamgiri, vol-1, p-4 [2] Hidaya vol-1, p-26