A.K.A. "the cheater pass"
Here in the North East it does little good imo. Or to politely re-word, I have found little use for such (grin).
The functions theory would be to apply a low pH on high pressure to bring the pH on the vehicles surface from high to slightly low or near neutral to aid in drying on wash packages with chemicals designed to bead water in the shine & protect steps followed by blowers. This would likely be used after a low pH followed by high pH presoak, low pressure passes or two high pH passes. The theory then would be to apply another low pH pass on the first high pressure to further lower the residual surface pH to ideally slightly low, with the cleaning benefits of the alkaline surface prior.
This theory may actually work in certain soil load regions such as those that tend to be dry and dusty. IMO the problem is it?s normally based on just one pass of presoak rather than two. It?s really not a cleaning step but rather a surface prep step.
To summarize IMO, it?s really a luxury added process for those attempting to tweak how dry a car is. Yet, I suspect in most washes in reality it has eliminated the very important second pass of presoak applied at low pressure. In the second scenario it has become a ?cheater? process, likely affecting the number of clean cars the bay puts out in a negative way. Ultimately in the second scenario IMO it is a waste of product and money.
In my case I find it best to remove it all together 100% of the time. There are better, more effeciant ways to improve water beading these days.
Regards,
Bill I. The Chemical Guy