Everybody that has to do with carpet cleaning has heard the word shading use in some context or another. The question is: do you know what it means?
Shading means just what it says: the carpet appears to have light and dark patches, as if shadows are thrown all over. Unfortunately these shadows are not, unlike after vacuuming or brushing, removable.
The Shading Phenomenon only occurs on piled carpet (velours) and is caused by an irreversible pile reversal (see illustrations below). In laymans terms: the pile has fallen over and reflects light differently than before. The affected area therefore has a spotty, shady, dirty appearance (says the affected party).
Normal appearance of a velours.
Velours with a local pile reversal: Shading.
What is the cause of this phenomenon? The answer to this question is not clear cut. For this reason most carpet manufacturers will enlighten the buyer in regards to this occurrence before the purchase in order to avoid liability suits.
However, there are a number of possible causes: air currents, temperature gradients, magnetic fields or mechanical influences.
For the affected party it is easiet if the carpet has just been cleaned before this unsightly appearance shows up (at least that is how it is presented very often).
Just so in the following case:
Case site: a large office building. Over several floors the same uniform coloured, high quality, grey velours from a renowned manufacturer was installed by glueing it down full surface.
The building service contractor, who did maintenance and special cleaning in this building had cleaned the carpet only a short while before. High traffic areas had been cleaned using extraction cleaning and other areas using the pad cleaning system.
After cleaning had taken place the customer complained about a spotty, non-uniform appearance. He felt that the carpet had been ruined from the cleaning.
The following photographs from the case site will give you an impression, dear readers, what the customer was talking about.
Shading in the walkways, in front of elevators,
in the hallway always in front of entrances to the offices.
The almost rectangular shape in this case leaves room for other possibilities...
It is obvious that this appearance has not been caused by cleaning. The individual shadings are too specific, especially regarding their location - had it been cleaning the appearancees would have been more random and more spread.
In this case shading was easy to diagnose and it was also possible to formulate a reasonably firm suspicion as to the cause: since the shading appeared in throughways, between hallways, or from hall to office etc., the air currents are most likely to have been the cause for the pile reversal.
In addition an area that is depicted above left room for speculation that a dirt mat with the wrong backing may have been used in this location and so caused the pile reversal.
In no way was the cleaning responsible for this condition. Another factor that supports this conclusion: in no other floor, where the same carpet on the same substrate was installed and where the cleaning was carried out in the same manner, did shading appear.
The customer was informed of the results and the conclusions. It was also pointed out that manufacturers have, in special cases, shown goodwill and replaced affected areas.
Not always is finding the cause so straightforward. In many cases the reason behind this appearance cannot be determined. Even in the case described above one question remains unanswered: why only on one floor?
As a carpet cleaner one should be informed about this phenomenon so that the customer, should it be apparent before cleaning, may be informed about it. Even if it is not visible it may be advisable to inform the customer. This may save a lot of trouble after cleaning and it makes you look more professional.
We hope that this example from reality has brought the phenomenon of shading a little closer and that knowledge about it will help you be more confident about cleaning carpets.