Answered by Shaykh Abdurrahman ibn Yusuf Mangera
Is kohl considered a preventative to letting water touch the skin during wudu?
Assalamu alaykum
Kohl (surma, antimony) is dust and soluble in water. When using water it will normally make the kohl smear, and if one has used sufficient water it should not prevent water from reaching the skin. If sufficient water was not used then it is possible that the water may be absorbed by some kohl particle and not reach the skin. Using sufficient water will ensure that the skin has been wetted and the wudu is valid. And Allah knows best.
Wassalam
Abdurrahman ibn Yusuf