Base coat

This type of nail polish is a clear or milky colored polish formula that is used specifically before applying nail polish to the nail.[6] The purpose of it is to strengthen nails, restore moisture to the nail, and/or help polish adhere to the nail. Some base coats are marketed as ridge fillers which can create a smooth surface, and reduce the appearance the ridges that can appear on unhealthy nails or due to aging. Base coat may also help keep nails from being stained a yellowish color by colored polishes.