Furthermore, the process is conducted at atmospheric pressure and in order for the emulsion product to emerge at a temperature of less than 100° C. then it is found in practice that bitumen cannot be fed into the emulsifier at more than 140° C. Higher temperatures for the bitumen feed require lower temperatures for the water feed.

This causes skin-hardening of the bitumen on contact of the two feeds and emulsification becomes very difficult. This temperature factor places a limitation on the types of bitumen which may be employed in bitumen emulsion manufacture by this route. A recent development, employing pressures slightly greater than atmospheric, involves cooling the product so that it can emerge from the mixer at below 100° C. This entails extra equipment and is difficult to control.