It's an interesting question. The last thing you need is an expensive carpet shrinking after it has been cleaned - thus rendering it, well possibly useless! You may want a carpet cleaned for health reasons, the visual aspect - or even after decorating a room?, and why not - it's a sensible thing to do, but disasters can happen! On a professional level we have seen many shrunken carpets, and we usually hear that they cannot contact the cleaning company who carried out the cleaning, which isn't good. So to avoid the stress, anger and worry of this phenomena we need to know why this is all happening.
What carpets can shrink?
There are general 2 types of carpet that can shrink: Axminsters & Wiltons. An genuine axminster carpet will have a wool face fibre (the bit that you walk on) and a jute backing yarn (the woven bit on the back) that interweaves with the wool fibre. It's pretty hard to shrink an Axminster but when the jute becomes wet through poor cleaning, then the backing could shrink.
The wiltons that can shrink are what we call Belgian Wiltons because traditionally a lot of these are made of a polypropylene face fibre - with a jute backing, just like the axminster (this is opposed to a good quality wilton which is made of wool). But because the polypropylene cannot hold on to hardly any moisture, it goes straight to the bottom of the pile into the backing, and shrinks the carpet. To check if you have a belgian wilton, peel back your carpet, and see if the pattern is duplicated and visible on the back - the same as the face pile. It's not a 100% check because you may not have a polypropylene pile fibre - but if you do have this, get the cleaning company to double check prior to cleaning.
Why Do They Shrink?
The main reason why they shrink is down to poor cleaning. What I mean is, it's either underpowered equipment or just bad technique. If the cleaning machine is cheap (and thus small) it cannot extract enough water out of the carpet, which means the carpet may then shrink. Bad technique could just be down to cleaners applying too much pre-spray cleaning agents, and too much water in the rinsing action. The physical action of why the carpet shrinks is the jute backing (I call it backing but it is the base to which the face fibres weave on to) when wet, essentially swell up and expand, thus needing more space and causing stress on the structure. It's this action that causes the shrinkage.
How Can You Avoid Them Shrinking?
Well if you have a belgian wilton then it could still be cleaned - but it needs to be done properly and safely. But there lies the problem, how do you know how to get it done - without it shrinking? By choosing a cleaning company that has extensive training on these issues is a good indicator of reliability, but one who also uses the most powerful machinery possible will usually ensure your carpet is safe. Don't forget, if a good, highly professional cleaning company are ever in doubt about shrinking a carpet, they will check first to see if it is cleanable. If there is suspicion that it will indeed shrink, then it should either be left, or a low moisture clean undertaken.
Author: Kevin Loomes