The requirements of a road surface are:
- ability to withstand shock, abrasion, displacement and wear
- ability to withstand wet, drought, heat and frost
- economical.
In the early 1900s an emulsion of pure bitumen called "Colas" was being used for road construction and maintenance. No materials were added to the emulsion which were harmful to either animal or plant life. The Colas was applied at the same temperature as the prepared surface.
- Colas was found to be suitable for the heat of the tropics, in this case Ceylon. The emulsion was being used to recondition roads that were showing serious signs of wear.
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In some cases the emulsion was poured onto the surface with a bucket and spread evenly over the road with brooms. The road had to be washed and any mud caked on the surface had to be removed before the surfacing could be done or the emulsion could not penetrate and would flake off.
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- The Pressure Tank had hand-operated jets as well as the main jets on the tank. The standard bar could spray a strip 8 feet wide. Teams of workers followed the tank spreading hard stone "chippings" which filled the spaces on the road surface.
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This picture was taken immediately after a severe flood. The left half of the road was surface dressed with Colas and was unharmed. The right side was ordinary waterbound construction and was unable to resist the force of the flood.
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