Retarder can be used on horizontal & vertical surfaces to retard the set of the surface and allow the aggregate to be exposed. For Vertical Surfaces, spray the formwork prior to assembly. Allow the material to dry and coat it again just prior to assembling the forms. Do not spray forms with water prior to placing the concrete. Place concrete and consolidate using a pencil or concrete vibrator. 6 hours later remove all formwork and spray the surface with a pressure washer to remove retarded cement paste. A mechanical brush or light acid etch may be required to finish the surface.