Does Dwell Time Matter?

OxiFreshGuy

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Alright carpet nerds...After a year of purposefully testing this I'd like some answers or explanations...

What is the purpose of the 20 minute dwell time? I've had trashed carpets that clean up almost perfect right after pre-spray and rinse.

When I used to do CRB cleanings I noticed my pre-spray worked better if I agitated IMMEDIATELY while spraying. If I waited 20 minutes it was not as effective.

I had the mother of all tests the other day, I should have taken pictures. A polyester frieze, had not been cleaned in a year, 5 dogs in the home. Carpet had that horrible black square around the coffee table where the dogs lay and track into and outside of the house.

I was using Procyon and Flex Citrus-Solv, 1 scoop each in a 1/4 filled inline sprayer. One side of the room I sprayed and let dwell for 20 minutes. Meanwhile the other side of the room I sprayed and rinsed immediately. Truckmount was Blue Line Blue Wave, 200 degree heat at the truck (no measurement at wand), no pre-agitation, using Rotovac 360i. PSI set to 320.

Side A (Spray and Rinse Immediately): Took me 15 minutes to clean, had to spray and rinse all of carpet twice. Came out 95%

Side B (Spray and Dwell 20 Minutes): Started cleaning after 20 minutes, did not look as good as Side A after first rinse. Sprayed and let dwell for 10 more minutes and rinsed again. Still did not look as good. Sprayed and rinsed immediately, looked as good as side A. Total cleaning time 40 minutes.

Is the dwell time not as important for polyester due to its hydrophobic properties? Is it better on Nylon? What's the deal!?!?!

Extrapolate this to every room in the house and sheesh that would be a long time on the job!
 
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Dream Clean

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Dwell time only matters for the first 5 minutes or so really. And that's just to give it time to penetrate through layers of gunk. a CRB negates a lot of the need as well since it pushes the prespray down into the fibers by force.
 

OxiFreshGuy

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My understanding of pre-sprays is they create soil suspension.

Try putting pepper flakes into a bowl with water, watch how the pepper flakes spread out equally (this is also how scientists first figured out how many molecules are in an atom, don't ask me how lol)

Now take your favorite pre-spray, this time mix it with the water before pouring your pepper flakes in.

One of two things happens usually.

1. The pepper flakes simply don't move, wherever it hits the water it stays.

2. The pepper flakes all stick and clump up together.

I always preferred pre-sprays that clump together.

But something interesting is, after 10 minutes sitting in the bowl, the pre-spray loses its effectiveness and the pepper flakes will spread back out again. Now obviously pepper flakes vs smaller dirt particles but it is an interesting observation.
 

Jim Davisson

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Chem concentration affects dwell time. I have some small one room high rise jobs I do frequently and to save time I increase chems, but put them down lightly twice at higher concentration.

Side note: I vary the 4 basic ingredients used my my prespray based on fiber type and soil load.

There are exceptions to this of course but in general it saves me time.
 
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Todd the Cleaner

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Working with two people on the truck I always prespray then scrub immediately, no dwell time. The second person starts with the wand as soon as I finish scrubbing the first room. By the time the wand is on the carpet it has been about 10 minutes since I presprayed. Cleans up great.

I have noticed especially on polyester that scrubbing makes a huge difference.
 

mrotto

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why wait to prescrub. Do like Todd and I do, scrub immediately after prespray. The dwell time is the time from application to the time of extraction so actually using the CRB does several things - lifts the fibers, agitates the prespray into the carpet and gives the prespray the time it needs to remove the soil from the fiber (dwell time)

in other words, the the dwell time is included while you use the CRB
 

brian3180

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My understanding of pre-sprays is they create soil suspension.

Try putting pepper flakes into a bowl with water, watch how the pepper flakes spread out equally (this is also how scientists first figured out how many molecules are in an atom, don't ask me how lol)

Now take your favorite pre-spray, this time mix it with the water before pouring your pepper flakes in.

One of two things happens usually.

1. The pepper flakes simply don't move, wherever it hits the water it stays.

2. The pepper flakes all stick and clump up together.

I always preferred pre-sprays that clump together.

But something interesting is, after 10 minutes sitting in the bowl, the pre-spray loses its effectiveness and the pepper flakes will spread back out again. Now obviously pepper flakes vs smaller dirt particles but it is an interesting observation.


If you had a surfactant in your pre spray, which lowers the surface tension of water so the solution can get to where it needs to be so it can clean, then the pepper would fall to the bottom of the bowl. Normally after I pre spray the spots are already gone by the time I am done agitating. Then I clean. 2-5 minutes dwell time at best.
 

beau

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So things I've noticed.

Dwell time helps loads. But only for about 5-10minutes. After that I don't see much improvement. But if you let it sit for too long without apply moisture/more spray it can start to dry out. This has the opposite effect. As it seems to clean worse.

So if it's hot/a sunny spot on the carpets I'll spray a little more to help it stay moist. I also don't start opening windows till after I'm done a room.

I also don't dwell them agitate. I'll spray and agitate it right away. Then by the time I get the hose and wand ready it's go time. Doesn't need much more dwell than that.

Your cleaners makes a difference too. I had to experiment with a few brands before I found one that didn't need much dwell time. Been super happy with it since.
 

rob allen

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I personally feel 5-10 mins dwell then agitate is superior.
 

Prestigecarpetclean

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Im glad you brought this up @oxi ive ben wondering the same thing 3 jobs on the books yesterday last job was biggest 5 areas and long hall poly carpets empty home. Tenants had dogs used high ph enzyme prespray mixed 8 oz plus spiked with bio8 2 oz in hydor force 4-1 tip sprayed down heavy 2 areas, set up hoses set up 360i got everything set up (20 minutes later) start flushing carpets came out ok was hoping for better next areas were really bad, it was getting late and im getting tired so i spray next area and half real well and start extracting immediately noticed more clean and pop than waiting for dwell. Only notice this problem in ugly ass poly tho dwell time on nylon urine soaked is were dwell really shines
 

OxiFreshGuy

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Well it would make sense...Nylon is 8x more absorbent than polyester and when dwell times were recommended 30 years ago most carpets were Nylon.

Same reason people still "kick" their car tires today...why? Because our ancestors use to kick their wagon wheels to check for sturdiness lol, it's a habit that has continued for 200 years.
 

wandwizard

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IMHO dwell time is all about penetration and suspension of the soils. Sometimes it will be the most important thing while other times not important at all. Agitation pretty much reduces dwell time from 5 to 20 minutes down to the very second you hit that carpet with your agitation machine or tool. IMHO there is no need to wait 20 minutes and then go in there with a crb or 175, etc. However, what if you have no way to agitate and you have an extremely stubborn soil and carpet fiber to deal with? Then you need that dwell time a lot more and hopefully, the right chem for that particular soil and fiber or you're gonna be working up a steep hill to get that thing cleaned and in some cases, you may be fighting a losing battle.

Another aspect of this is that some presprays DO need more dwell time to do their best work while others work seemingly on contact. Enzymes generally do their best performance with a little dwell time, but still, agitation will take you from point A to point B a lot quicker. It is very rare for me to wait even 15 minutes to actually start cleaning. Just the time spent agitating is normally plenty to prepare even the worst carpet for cleaning.
 
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Scott W

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20 minutes dwell time is longer than needed for most situations. 5 to 10 minutes that Rob mentioned works better.

The best dwell time for the job depends upon the product you are suing, the fiber you are cleaning type of soil and how heavy the soil is.

If you have greasy hands, you know that would not get clean if you just stuck them under the water and pulled them out. The soap needs time to work. But, the agitation should start right after the cleaning solution is applied, just as you would begin rubbing your hands together as soon as you got them soaped up. Agitation and dwell time should be happening at the same time.

As detergents and pH builders react with soils, their effectiveness drops. If you are using a product with good buffering, they keep working for a longer time. This longer dwell time would be effective if needed. If you are using a product without good buffering, the product will stop working pretty quickly. Longer dwell time would not help at all. This can be illustrated by the soap suds level in a sink full of dirty dishes. As the soil on the dishes reacts with the dish soap, the suds level decrease dramatically. The cleaning agent is becoming less effective.