Temperatures Heating Point of Application Roofing bitumens should not be overheated beyond their allowable maximum temperatures since overheating can modify their physical characteristics and may affect the performance of the installed roofing system. The ideal viscosity for coal tar at the point of application has been determined to be 25 centipoise. This viscosity is appropriate for both mechanical spreading and mopping applications. The ideal viscosity for asphalt at the point of application has been determined to be 75 centipoise for mechanical spreading and 125 centipoise for mopping applications. The temperature range to achieve these ideal viscosities (Equiviscous Temperature - EVT) at the point of application and the allowable maximum heating temperature are normally provided on the labels or with the shipping documents. In the event the maximum heating temperatures or the EVTs are not distinguishable, use the recommendations in Table 1. Bitumen Type Max. Heating Temp. Point of Application Temp. (EVT) F C F C Coal Tar Pitch. Type I 400 204 360 +/- 25 182 +/- 14 Steep Asphalt. Type III 525 275 450 +/- 25 232 +/- 14 Extra Steep Asphalt. Type IV 525 275 460 +/- 25 238 +/- 14 For mechanical spreading of asphalt, use the higher end of the temperature range.  Return to Application Considerations and Specifications