Wax Solution - Surfacing Agent
"Wax solution" is paraffin wax dissolved in styrene that is added to polyester resins and gel coats to prevent tackiness.
The wax in the curing process will rise or "bloom" to the top creating a barrier between the resin and air. Oxygen inhibits the chemical reaction needed for a full cure. However, the wax surface must be sanded prior to applying a second coat.