In spreadsheet, cost per linear foot is the application rate by product (derived) applied to minutes of use.
Desired effect refers to end result of using product -
drying agent imparts hydrophobic effect on surface.
Assume a manufacturer of
drying agent determines it takes three drops of
drying agent per square inch to impart hydrophobic effect causing water to bead up.
Thus, four or five drops would not cause an additive effect (wasting product) and using one drop would not cause the desired effect – beading.
Yes, the “waterfall” in tunnel is a show but it is also an application method involving rate (time and amount of product use).
For example, if glow foam doesn’t cover a side panel or is of insufficient concentration – the desired effect will not be achieved.
This problem is minimized in automatic wash because the machine can be designed and calibrated so distribution is a constant.
With a wand-bay, you can have a constant coming out of the nozzle tip but you have no control over how customers distribute the product on the car.
If customers zip around the car applying an insufficient amount of glow foam, the desired effect may not be realized. If customers apply a lot more of the product than is necessary (using more minutes), the substantially higher application cost of this product will erode margin.
Since many self-service operators need all the help they can get, I certainly would not suggest concepts or ideas having the opposite effect.
Selling glow foam is simply easier with tunnel or in-bay as well as more profitable because of the difference in revenue model in comparison to wands.