I have a client that I do carpets for about twice a year for a couple years now. After the first cleaning he asked why the area in front of the door didn't look very clean, I explained to him the carpet there is just worn and while its clean, it will always have a darker appearance. He was fine with that but it comes up after every cleaning. I gave a more detailed explanation about light reflections and micro abrasion. Okay. Still askes at next cleaning. So he emailed me yesterday about it, said he just doesn't get the whole light reflection thing. So I emailed him back this paint doc drawing I did just for him and the following explination:
"In the picture I provided, image A represents a carpet fiber from a newly installed, perfectly clean carpet. It has no dirt and has received no wear. Its a smooth structure. The light particles (represented by yellow lines) hit the fiber and are reflected and received by our eyes. The more light our eyes receive, the brighter the object reflecting the light appears. White appears very bright because it reflects the most light. Black is very dark because it does not reflect much light.
Image B shows a carpet fiber that has become dirty. In addition to the darker color of the dirt particle, which absorbs more light than it reflects, they also create a rough surface that blocks some light reflection and can even cause it to be reflected away from us. This lower level of light reaching our eyes is why the carpet looks darker when dirty.
Image C shows a clean carpet fiber that has become worn. Notice the indentations on the fiber, these are micro abrasions. Cuts and cracks in the fiber. The fiber is no longer a smooth surface. As a result, the fiber may be the same color quality as fiber A, however, the micro abrasions cause some light to not be reflected to where our eyes can detect it. Because our eyes are receiving less light, the carpet appears darker, which we relate as being dirty, even though its not."
I sent it off and got a reply about 30 minutes later. "Thank you for that explanation Robert, this makes a lot a sense now."
I don't know if my info was 100% but he seems convinced this time that I got the carpet clean.
"In the picture I provided, image A represents a carpet fiber from a newly installed, perfectly clean carpet. It has no dirt and has received no wear. Its a smooth structure. The light particles (represented by yellow lines) hit the fiber and are reflected and received by our eyes. The more light our eyes receive, the brighter the object reflecting the light appears. White appears very bright because it reflects the most light. Black is very dark because it does not reflect much light.
Image B shows a carpet fiber that has become dirty. In addition to the darker color of the dirt particle, which absorbs more light than it reflects, they also create a rough surface that blocks some light reflection and can even cause it to be reflected away from us. This lower level of light reaching our eyes is why the carpet looks darker when dirty.
Image C shows a clean carpet fiber that has become worn. Notice the indentations on the fiber, these are micro abrasions. Cuts and cracks in the fiber. The fiber is no longer a smooth surface. As a result, the fiber may be the same color quality as fiber A, however, the micro abrasions cause some light to not be reflected to where our eyes can detect it. Because our eyes are receiving less light, the carpet appears darker, which we relate as being dirty, even though its not."
I sent it off and got a reply about 30 minutes later. "Thank you for that explanation Robert, this makes a lot a sense now."
I don't know if my info was 100% but he seems convinced this time that I got the carpet clean.