This is a very common question, perhaps more so here in the UK where so called Snowfoam has been a standard part of the wash cycle for some years.
Do snowfoams facilitate a touchless wash?
Unfortunately the answer is no, 9 times in 10. This is the case whether one is doing a rinse or using a high pressure washer and does not tend to matter whether you are using a mild product or something which is bunged full of alkalinity (this latter has a massively enhanced cleaning power). The only time you can achieve such results are when your paint is well protected and when you have very light soiling.
What then is the point behind snowfoam?
Snowfoam is used to try to enhance the cleaning process compared to other techniques. By using a foam which dwells, one can enhance the wetting of the soiling on the surface, something which is fundamental in cleaning.
Why does it not produce a touchless wash?
Many of the soils a vehicle picks up are hard to 'wet'. This need not even be bonded soiling, even oily films (traffic films as we would refer to them) will fall into this category. Whilst the foam and the surfactants within will work to wet and remove this, it can often need much stronger (and much more alkaline) conditions to break this film down into aqueous solution (i.e. your rinse water).
So how should one use snowfoam?
In my professional view, snowfoam is part of the wash process, not the wash process itself. It should be used to help loosen any contamination which can easily be liberated without mechanical work (i.e. scrubbing). It can be used interchangably with a non-foam prewash (which, IMO, is a massively more economical, effective and less messy approach). One should assume that once foaming is done, there will be a semi-bonded film which will probably require a mechanical wash. As others have said, you can do multiple foams to try to further minimise the presence of abrasive particles before touching the surface with a mitt. I would suggest that one might consider a prewash if doing multiple foam washes since this might negate the need for a second foam/prewash process (thus saving time in the routine).
To my mind, foam is more of a user fad than something essential or ground breaking. However, detailing has to be fun as well so don't rule that out - if foam makes your process more entertaining and helps motivate you to do the rest of it better, then who is anyone else to argue!
LOL
