I come across a lot of customers who perceive that their carpets will take a lot longer to dry, when the weather is cold or wet.
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People are too quick to judge dry extraction cleaning based on the horror stories and incompetent operators. There are horror stories and incompetent operators of all methods; none more so than Hot Water Extraction!
Some words on "Shake n Vac" and then I'm of to bed as I don't want to upset the apple cart again (we've only just got all the apples back on it), and I'm tired as I've had 3 weeks of a full diary 6 days per week, (of this dastardly low moisture carpet cleaning)

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Dry Extraction: People who assume that this method involves simply vacuuming, putting down dry extraction compound, brushing it in, then vaccing it out, really just show their lack of understanding of the method.
The key is in the word Dry "Extraction" ....... In effective use of this method, the sponges are to remove dirt and soil that has already been pre-treated, agitated and broken down from the fibres. Just the same as if you Truck Mount fans turned up and simply sprayed a detergent rinse on the carpet you wouldn't get good results, so it is with dry extraction.
After the pre-vac the carpet must be pre-sprayed with appropriate chems for the soil that's residing in the carpet. (So something like M-Power for organic soil types, and something solvent based or with a higher pH*, if the soil is more oily or synthetic). Agitation of the pre-spray using the CRB machine is then the key "soil breaking" stage.
Only when I am confident that all removable soil has been split from fibres would I then apply the dry extraction sponges. They will then absorb the soil and the pre-spray**.
The result when this method is used effectively, is removal of any level of soil; not just "mild soiling only" as some HWE'ers love to state! Dry Extraction can completely restore a trashed carpet, WHEN executed correctly, with knowledge and experience.
*I never use a pH above 8 with Dry Extraction because although the sponges are pH neutral and will bring down the pH in use, they clearly aren't as acidic as an acid rinse.
** Bear in mind that all of the Pre-Sprays that I use with Dry Extraction are technically speaking 'non-rinsing', as in they do not need to be rinsed (ie... M-Power), however the dry extraction picks up the pre-spray and encapsulated soil, and most importantly, contributes to the drying.
When you hear people like Martin_606 say that he's cleaned all levels of soil from carpets over the last XX years, it's because he has the expertise to clean properly, regardless of the extraction system, not that he has a nice stance when he does his "shake n vac".