This International Standard specifies a method of measuring — the time required for the temperature of a solution of unsaturated-polyester resin and a catalyst, heated in a thermostatically controlled bath at 130 °C, to rise • from 80 °C to 140 °C, • from 80 °C to the maximum temperature reached; — the maximum temperature reached; — the speed of the reaction, determined by drawing a tangent at the point of inflection of the temperature/time curve. It applies in particular to unsaturated-polyester resins processed at a temperature higher than 100 °C. NOTE — The results are closely linked to the conditions. The aim of this International Standard is to define them as exactly as possible, particularly the following: a) The quantity and form of the resin sample being examined (test tube diameter, height of resin in the tube). b) The rate at which the sample is heated in the bath. For example, the use of a liquid having a relatively low heat capacity (ethylene glycol, silicone oil) leads to slower heating. c) The type of thermometer used. Thermometers having a response slower than that of a thermocouple, and resistance probes having too large a heat-sensitive element, are unsuitable. d) The position of the heat-sensitive element in the resin, both heightwise and relative to the axis of the test tube containing the resin. e) The nature of the catalyst.