My wife and I debate this all the time. I still think that a fast dry stroke may have some benefit because it flicks the moisture off the fibers. I tend to do a lot of dry strokes fast and slow though. I also post bonnet.
Fascinating discussion. The passes and speed depend on the cleaning objective, as well as the pressure and flow rate? This will determine speed of wand and number of dry strokes. If you want to know cleaning (wet) passes, it's the same thing but includes achieving "effective" soil suspension. If not achieved, additional passes may be applicable to muscle additional soil separation, by leveraging the heat, pressure and flow of the TM system. If you run a 6 jet wand with 015 orifices at 400 plus, you're up in the 2+ GPM. Higher moisture, expect more dry passes.
Are you rinsing or flushing? Because they are not the same. Under general soiling conditions 85/15 based on an application rate of 200 sqft per gallon of preconditioner, it only takes a flow rate of just under a half gallon to rinse and neutralize with 2 passes @ a rate of 1 second per sqft. Higher pressure and flow you could technically move faster, however most slow down because they are relying on the TM system where the extraction phase completes the "soil suspension" phase. This is key to understand when it comes to cleaning "piled" textile floor coverings. Soils aren't really "suspended". Prepared yes, suspended no. The water dissolution of the soil laden cleaning solution does the actual suspension while simultaneous extraction occurs.
Regarding the 2 wet passes and 2 dry passes. Understand and know where it comes from,
lab testing. A protocol written circa This is a foundational rule and can be achieved with generally cleaning like following the 2 wet passes and 2 dry passes. So, some environments may require more wet passes and more dry passes. Don't follow the conventional more is better unless it's applicable.
This is why some clean with 150-250 psi with flow rates under 1 gpm to avoid wicking and wick back. I'll get into how moisture really works when it comes to increasing volume or flow. Bill Bane knew! Work smarter, not harder. You're not cleaning the "effective pile" (as in flushing it) you are "wet" cleaning the wear surface.
Even I don't have a strict rules on wand strokes. If I'm near a wall or a less soiled area, it's faster and if it's in the traffic lane slower and even a "truck mount stroke". I use portables when I extract and I don't worry about water consumption. I hold the trigger down and stroke the heck out of it, followed up by dry passes I think necessary for me not having to return for a complaint and follow up cleaning.
I believe 2 passes should be the minimum as well as the additional 2 dry passes as far as a general rule or guideline. Particularly if a portable extractor with heat, where the heat needs to be sustained.
We can't compare all carpet cleaning because carpet is often abused. The 2 wet pass and 2 dry passes under "normal" soiling conditions is applicable but in a restaurant setting where the traffic lanes are black from wall to wall, then 2/2 rule shouldn't even be considered.
The original testing protocol is in the
S100 2002 edition. Was supposed to be inclusive of all methods, however during development it was changed to primarily focus on Water Rinse Extraction (WRE). Why? The test method was later adopted by the Carpet and Rug Institute for their SOA "Extractor" and "Deep Cleaning system" testing. Very interesting, makes you think doesn't it?
