at the staging area the first and second components are mixed 12 to create a liquid compound the liquid compound is applied 14 to the surface of the substrate before the compound undergoes a substantial increase in viscosity and while the compound can still easily be distributed over the substrate and will be able to penetrate the substrate the liquid compound can therefore reach the desired penetration depth within the substrate before the compound reaches a high viscosity at which it is essentially no longer flowable at this point crust 18 has been formed alternatively mixing 12 can take place any time subsequent to application 14 this might occur for example if component 2 is applied to the substrate first followed by component 4 or if a dual nozzle applicator is used in the further alternative the mixing and application processes can be combined into a single process 16 the method may be modified by predetermining a desired delay period for the liquid compound to reach its maximum viscosity and adding a retardant to the liquid compound in an amount effective to correlate the time before the compound undergoes a substantial increase viscosity to that desired delay period controlling the rate of viscosity change in the stabilization compound is important in producing a final crust having the desired properties as.