What is shellac nail polish shellac is frequently described as a hybrid of the popular gel manicure with gels a thick substance is applied to the nail to build up a new surface the gel is hardened under uv light then smoothed and sculpted with an electric file before adding polish how long does a shellac manicure last almost every shellac nail treatment will last 14 days most people find that the nail polish stays in place for a full month but new nail growth may send them back to