"Shading" is a general description given to a
number of optical effects in the appearance of carpets under a variety of names such as
"tracking", "foot marking", "watermarking",
"pooling" or "pile reversal". These names can be used with slightly
different meanings by different people and so when discussing them it is always important
to make sure exactly what is meant.
SO WHAT IS
"SHADING"?
When a carpet is made it will usually emerge with all the
tufts in the pile parallel, pointing in the same direction and therefore having a uniform
appearance. However any localized alteration in the orientation of the tufts will result
in a change because the light will reflect in a different way either from the cut ends of
the tufts or from the sides which may have become exposed. This may give the appearance of
a colour change whilst in reality being only an optical effect. All textile
materials with a pile or nap may show areas seemingly dark or light depending on
at which angle the tufts lie in relation to the person viewing the
effect.
An official and internationally
recognised definition of shading is incorporated into international standard ISO 2424:1992
(para 9.1.3.1.8) which was drawn up, agreed and published by the International Standards
Organisation. It is shown in later on.
This is essentially temporary and typically appears as
footprints or small localised marks caused by scuffing of feet or dragging furniture. It
is likely to be more obvious in deeper or finer pile carpets (especially those without any
pattern.)
All these effects are temporary and can
be reversed by brushing the pile in the shaded area in the same direction as the rest of
the pile. Occasionally in some cases steam cleaning (preferably by a professional cleaning
contractor) or other treatment may be needed to restore the pile to optimum appearance.
This describes the flattening or crushing of the carpet
pile in areas of more concentrated foot traffic — especially
where it may be subject to a twisting action such as around furniture or corridor corners
or in doorways.
Once tracking is established
there is not much that can be done where it results from fixed building features such as
doorways. Furniture can be re-arranged from time to time to equalize the wear and to
minimise the difference between the trafficked and non-trafficked areas.
What may seem to be difference in shade can also be seen
when two different strips of the same carpet are laid in the opposite direction to each
other. This has nothing to do with wear and is purely an optical effect. (It is similar in
principle to the "lines" perceived in a grass lawn when the mower has passed one
way and then comes back in the opposite direction).
Patio doors or large picture windows.
Some form of protection, e.g. Blinds / nets are essential to
assist in preventing summer sunshine affecting the colour of your carpet. It ahs been
noted 'Pilkington K glass can be of benefit in reducing the effects the sun can have on
many fabrics. Pastel shades, particularly, are more vulnerable than darker, richer
colours. Woolen or wool-blend carpets will naturally react to sunlight and this could
affect carpets that have not been protected from the prolonged exposure to sunlight. In
light or very light colours, what looks like fading in the more frequently walked on areas
is often the optical effect of pile flattening in use and some surface flattening.
When a seam is required to be placed near a light
source ie: large windows / patio doors the seam can be more obvious due to a
peaking / tenting of the seam, this tenting effect occurs due to the carpet
being butted too tightly and not cut straight, it requires to be un-seamed and
done again. Please remember though that no seam is totally un-noticeable
and some degree of un-sightliness must be accepted. Yet again discussion should
have taken place.
Such an effect could not be corrected
once established (other than by re-laying one of the strips so that it lies in the same
direction as the other).
What may appear to be a shade difference when two widths of
carpet are laid side by side may be known as a hue difference which can ocure
when large quantities of carpet is laid in one location. one must ensure that
the specification states "From same dye lot".
The hue difference may ocure when a piece from the start of
the run is laid beside the last of the run. The hue difference is very minimal
and will almost in all cases not be upheld as a form of complaint as it will be
within tolerance.
This is really a texture visual effect usually found in twist
and loop pile carpets.
In twist pile carpet the twist may be tighter in one piece
than the other. This in my opinion should not be put up with, the person fitting
the carpet should stop, and report the matter and insist on a replacement, the
same should occur with the loop pile.
With loop pile what is more usual is a seaming problem where a
cut side is laid to a cut side because the loop is cut in places and not in
others, this can sometimes look awful but usually impossible to avoid. It should
be discussed prior to the work taking place, not taken for granted that common
sense is obvious.
You can see that the carpet pile in the lower half of the
picture is of a tighter appearance than the pile in the top half.
Occasionally shading can appear in random patches not
obviously the result of use nor for any other evident reasons. For carpet users and
retailers this is probably the principal area of difficulty because it can be permanent,
in that the shaded area cannot be brushed or steam cleaned away.
This type of shading may be referred to as "pile reversal" or
even (because of a resemblance to water spillage marks) as "watermarking" or
"pooling". Sometimes at the edge of the shaded area the pile material can be
intermingled and fused with surrounding tufts in a way which can be felt as well as seen.
"Shading" in a permanent sense occurs
comparatively infrequently and over the years has been the cause of continuing speculation
within the carpet industry. There are no known explanations universally acceptable.
There is clearly no one cause for the permanent forms of shading which can
occur in any type of pile carpet, ranging from a low-cost, synthetic fibre, tufted carpet
to a hand-woven oriental silk rug. It can even occur in a coconut fibre entrance mat. It
can happen to newly installed carpets which have left the factory in perfect condition or
it can occur after a more extended period. Other than "tracking" such shading is
usually a random effect and cannot be guaranteed to appear, nor not to appear.
Almost every carpet expert who has come across the problem has their
particular suspicions about shading and what can spark it off. Yet these remain only
suspicions because being both infrequent and random makes it difficult to research.
Some suspect that shading can be set off by changes in
temperature or humidity. On other occasions there are indications that it may arise from
unsatisfactory treatment received after leaving the control of the manufacturer or during
installation. (For example where it may have been folded or bent while still
rolled).
LOCATIONAL
Permanent pile reversal does sometimes seem to be related
to a particular location. Over the years there have been many reports of where shaded
carpet has been replaced only for the problem to happen again in almost the same place.
From Australia comes a report of carpets originally installed in one place
and showing no previous sign of shading then developing the phenomenon when re-laid in a
"shading-prone" location. Yet it has not
been possible to isolate the specific factors responsible, although floor temperature,
humidity, air currents, static electricity or floor level irregularities have all been
advanced as possible causes.
All changes in appearance, whether caused by compression or by a change in
the inclination of the pile, are more noticeable in new plain velvet carpets or on carpets
with small motif patterns on an open background. These changes will also be more or less
noticeable depending on the direction of the main light source, or its intensity and the
degree of lustre in the pile material.
Unsurprisingly the optical effects appear less obvious in more heavily
patterned products. In plain or near plain carpets permanent shading effects are more
noticeable and therefore of more concern to consumers. Shading, whether permanent or
temporary, has no effect on the wear life of a carpet.
The effects of normal day-to-day wear are more noticeable on plain velour
carpets than on patterned carpets; on light or delicate shades than on dark or vibrant
colours; and on fine-textures, than on coarser spun, chunky or hard twist yarns.
Shading can occur in carpets all over the world. The German Carpet
Research Institute for example started a major research programme some years ago to try to
find answers to why some carpets and not others should be subject to random patches of
shading. Similar research has been carried out in the United Kingdom, France, the United
States of America, New Zealand and Australia, so far without any generally applicable
results.
Regarding the more permanent forms of "shading" the consensus of expert
opinion is that:
— it can occur in any cut pile carpet, rug or mat, including hand knotted, tufted,
woven, bonded, knitted or hand made floor coverings. See PILE
REVERSAL
Its occurrence has not been linked with the various different carpet
manufacturing processes or the component products used in carpet making.
It can occur in carpets made from all common carpet fibres and any blends
of different fibres) for example wool, nylon (polyamide), polypropylene,
polyester, acrylic etc.
Certain locations can be conducive to shading.
There are no indications that shading is associated with any maintenance
method.
Shading is not, as once suspected, associated with any dimensional
changes in backing fabric and can occur in carpets with a woven or non-woven back,
a secondary backing or with a foam backing — and
irrespective of whether laid with adhesive or gripper.
There is no correlation between the value or quality of a carpet and
whether it may be affected by shading.
Although there are no proven connections between the way a carpet is
installed and any subsequent shading, it is always desirable for any carpet to be
professionally fitted and with an underlay of a standard appropriate to its worth.
Shading cannot be attributed to a fault of manufacture.
(YET)
EXTRACT FROM ISO STANDARD 2424:1992 (PARA 9.1.3.1.8)
"Shading": A change in the appearance of a textile floor covering
due to localised alterations in the orientation of the fibres, tufts or
loops. This is not a real change in hue, but a difference in light reflection, which can
occur as a temporary shading, tracking or pile reversal which are defined as follows:
a. Temporary Shading: A reversible localised change in orientation of
the pile of a textile floor covering during normal use (sometimes described as a normal
characteristic of certain cut-pile textile floor coverings).
b. Tracking: A gradual change in appearance of a textile
floor covering from edge to middle of a narrow band, caused by repeated walking over the same area which
may result in localised change in pile orientation and may be irreversible.
c. Pile Reversal: An
irreversible localised change in orientation of the pile of a textile floor covering, the
boundaries of which often assume a rough matted texture due to the confluence of pile
lying in normal and reverse directions. This phenomenon has different names in different
countries".
Grey
Scale Chart in use.