How do I know how much product to apply to the tire and how can it be measured?
Generally speaking the optimum coating of inside paint is one that is evenly spread across the entire inner face of the of tire reaching across the tire from bead to bead. For outside paint the coverage should be a thin even film applied to the areas of the tire that benefit most from the use of an outside paint, typically this would be the tire sidewall areas and perhaps an area around the external shoulders. The tread area is often not coated with an outside paint.
Once the optimum coverage is obtained, using the visual guidelines mentioned above then the actual coat weight maybe determined. This may be achieved by either measuring the shot weight or using pre-weighed patches adhered to the inside or outside of the tire, the so called “patch-test”. The shot weight may be determined by using pre-weighed polythene bags placed over the spray gun heads to capture the amount emerging from the spray gun head when it is activated. The “patch-test” involves applying pre-weighed patches applied to the inner-liner or outer face of the tire, depending whether one is measuring the volume of inside or outside paint being applied. In the case of the plastic bag technique it is usually best to measure an average of five to six activations of the spray gun to simulate the spraying of five to six tires, and then calculating the average amount in order to obtain better accuracy. In the case of the “patch test” it is better to apply three patches spread around the inside or outside of the tire to help determine the distribution of the film around the tire. In both cases the measured coat weight is obtained from calculating the differences between the pre-weighed empty bags or pre-weighed clean patch, and the weight after the tire is sprayed or the spray cycles simulated, depending on which technique is being used. An experienced release agent supplier should be able to provide support in this process.