Phenolic yellowing is an unusual name and phenomenon. It happens a lot with rugs and carpets. I will try to explain this in most simple way possible. This explanation will shed a light on lot of doubts, hopefully!
Most of the people confuse it with the original carpet colour being retained under it. Yellowing can occur with carpets of any colour. The primary reason for this is Off Gassing. In the case of carpets, a chemical known as Butylhydroxyltoluene is used as a preservative. It is used either within the carpet on or latex of tufted carpets and in the under lays also. When a rug is placed on a carpet, it traps air and ceases the carpet from breathing. Then the chemical would float in the atmosphere and it reacts with the air and discolours the fibre of carpet. If a carpet does not contain BHT or if the carpet is not a tufted pile, even then yellowing can be possible.
Secondary backed latex glue back of the carpet may be the reason for yellowing. Smooth textured backing will have no resemblance to pile of rug. Basically, the Off Gassing trying to escape from the rug is being caught by the carpet is the reason for this yellowing action. It can never be cleaned. It is permanent.
Technical definition of Phenolic yellowing
This yellowing is caused due to the presence of Phenolic compounds in the textile material and it reacts with oxides of nitrogen in an alkaline medium. This phenomenon is associated with storage of finished textile material. They are packed in polyethylene materials or cardboard cartons. Aromatic amines (Para phenylene di- Amine) and Phenolic compounds (Butylated Hydroxyl toluene) are used as anti oxidants and stabilizers in organic polymer packaging materials and in foams and lubricants. There are Phenolic derivatives from lignin in cardboard. They form yellowing precursors
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Just imagine your carpet which you had purchased lovingly shrank after you got it cleaned! It will be almost useless if this happens. You might get it cleaned for decorative or health purpose. It is a sensible thought to get carpets cleaned but sometimes it ends up in disasters. Professionally, we have seen carpets that got shrunk due to various reasons and many of the victims have called up to the companies to get it rectified but no response from their side. To get relieved from all the stress, worries, anger and tension of this phenomenon, you should know all about it at the first place.
Types of carpets that shrink
Generally, there are two kinds of carpets that shrink- Wiltons and Axminsters. Genuine Axminster carpets have wool face fabric (the front side) and yarn that has got jute as its backing (the woven one on the back of the carpet ) and it is interweaved with wool fibre. This carpet does not shrink generally but due to improper cleaning if the jute material becomes wet, then the back layer can shrink.
Belgian Wiltons are the type of Wiltons that generally shrink as these carpets contain fibre named polypropylene and has a backing of jute like Axminster. This fibre cannot hold any moisture content and the moisture gets accumulated at the bottom of the carpet pile and it wets the backing as well and because of this, carpet shrinks. To check whether the carpet is Belgian Wilton, turn over the carpet and see whether there is same pattern visible on the back. It will be the same as face pile. If it is Winston, then call up the company to check prior cleaning.
Reason for shrinking of carpets
Carpets shrink due to improper cleaning. If we use under powered equipment or bad techniques of cleaning then they may get spoiled further. If the machinery used to clean is small and cheap, water cannot be extracted properly from the carpet causing shrinking of carpets. Bad techniques include applying more of the pre spray agents and using large amounts of water for rinsing. Jute fibres get swelled and expanded when they are wet. It then occupies space than usual and causes stress on the frame of the structure. Due to this expansion, shrinking occurs.
Avoidance of carpets from shrinking
If it is the Belgian Wilton carpet that you have, then it can be cleaned to a extent but it should be done efficiently and with care. But the question is how can it be done without shrinking it? You will have to choose a good cleaning company that has very good experience on using these techniques and they must use powerful machinery also. Professionals from good company will check whether the carpet will shrink or not before starting the process of cleaning. It there is a possibility that cleaning can shrink the carpet, it is better to leave it or it is to be cleaned by using low moisture technique.
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