This International Standard specifies a method for the determination of the gel time of prepregs made of continuous reinforcement impregnated with epoxy and/or unsaturated-polyester resin. The method is applicable to most prepregs with a width in the range 300 mm to 1000 mm. It is not suitable for very narrow prepregs (for example narrow tape), nor for prepregs with a low resin content. NOTE Other methods of measuring gel time exist. These methods are based on principles which differ from those described in clause 4, and the results obtained using such methods may be different from those obtained with this International Standard. The method described below is the traditionally used one and is widely accepted, even though it may be somewhat obsolete.