The major carpet manufacturers feel that a PROTECTANT is important to have on the fibers, and they go to great efforts to apply it and to teach cleaners how to work with it. Here is why it's so important to apply protectant to newly-cleaned carpet or upholstery:
1) to protect the soft shiny surface of the fiber (the same as car wax protects paint),
2) to resist soiling,
3) to fill the voids in the fiber before soil does,
4) protected carpets release soil better for vacuuming and for the technician.
The protectant is removed by foot traffic, vacuuming, and harsh detergents. It should be reapplied BEFORE the soil finds it's way into the fiber. The protectant performs better when it is groomed in north/south then east/west. In short the carpet lasts longer, looks better, the home owner is happier with their investment, your job is easier, and YOU make more money!