Wool area rugs require a little more consideration when being cleaned than those made of cotton or artificial fibers. While steam cleaners do a good job on most area rugs, care should be taken when using one on wool.
Rugs can generally absorb a lot of punishment, but one of the problems with wool is that it is a natural product rich in lanolin. Just as you would not put your favorite woolen sweater into the boil wash, neither should you routinely use a steam cleaner on a genuine wool rug carpet.
If you have a wool area carpet that has been stained badly and all other cleaning methods have failed, a steam cleaner can be tried as a last resort. The deep cleaning treatment available using a steam cleaner will definitely do a better job than the more normal wool cleaning methods. The problem is what happens afterward. The hemp or hessian backing that so many wool rugs are woven on is very absorbent and takes a long time to dry properly. The lanolin rich wool encourages mold growth so it is very important that a wool rug cleaned by steam is dried very thoroughly.
Wear and Tear
Steam cleaners tend to be quite heavy and the steam injection heads sometimes operate at high pressure. To reduce potential damage to a wool area rug you should use a low pressure for the steam injection and keep the head moving so that the wool does not get scalded. The softness that is a characteristic of a wool area carpet is the result of the presence of lanolin in the fibers. Lanolin is easily destroyed by heat and the fibers become harsh and brittle. Although the steam cleaner dirty water might indicate that an excellent cleaning job has been done, only time will tell if some of that dirt was actually the lanolin being leached out of the wool.
Only the very gentlest of cleaning agents should be used on wool, especially with a steam cleaner. Again the importance of the retention by the wool of the lanolin cannot be emphasized enough. It is also important that the steam cleaner removes all traces of the detergent in the normal cleaning cycle. Detergent residues can make the wool fibers sticky, and they will get dirty a lot faster as a result.
If it is possible to raise the wool area rug off the floor while it is drying after being steam cleaned it will help prevent molds from developing. Some steam cleaners use a warm air circulation method of drying but this can be damaging to the wool fibers while leaving the rug carpet backing damp. A damp carpet is an ideal breeding ground for mold.
As long as a steam cleaner is not used as the cleaner of choice for wool area rugs, it is fairly safe to use with the safety of the rug in mind. Steam heat should not be used more than once a year.