We use the CHI Transformation Straightening System, which is Ammonia and Formaldehyde FREE. This service achieves permanent results that give you straight and frizz-free hair. Hair is permanently straight until it grows out. Every 4-6 months the regrowth can be retouched. We do charge by the hour and one can expect the service approximately 3.5 hours based on average thickness and length of hair. It can be applied to virgin and coloured hair but is not recommended for excessively damaged hair.