Hi Ian
I think that most well seasoned professional cleaning technicians within the industry understand that whilst heat is an effective source of energy to utilise within the cleaning process, it can cause damage if used inappropriately. Heat is only one in the list of armoury that we have at our disposal, along with Mechanical action, Chemical action and digestion, and even 'time' (dwell time of the cleaning agent). If we are aware that one source of energy i.e heat could potentially damage what we are cleaning then we are able to consider other energies within the cleaning pie to compensate for heat (or vica versa).
All I can do is to give you an outline of some of the experiences I have seen along my travels, and hope that this may help others steer clear of these hazards.
1. Heat distortion on Pile fabric acrylic velour suites (Dralons).
2. Burst twist of pile fibres using localised steam in removing gum.
3. Breakdown of carpet latex adhesive holding the primary backing to the secondary backing.
4. Lines left in Polypropylene fibres with excessive heat resetting the memory of these heat sensitive fibres.
5. Distortion of cotton velour curtains and loss of lustre with steam cleaning unit.
6. Distortion of synthetic velour curtains with steam cleaning unit.
6. Dyes taken out. and loss of colour on carpet, Upholstery, and curtains using steam.
7. Shrinkage of fabrics with steam heat, (and for that matter hot water extraction as well).
8. Cellosic Browning where incorrect angle of the steamer in use, has jetted directly in to the backing Hessian.
This should not be seen as purely singling out steamers, as many of these problems can occur with other cleaning systems as well. But as with any thing if someone does not understand the chemistry of cleaning and fibres, along with the appropriate cleaning techniques then they are leaving themselves wide open for problems.
I appreciate that many people will use these steam systems and have no problems, and at the end of the day it is not the equipment that should be blamed, as it certainly is a useful piece of kit. It is down to the operator to possess the knowledge in how to use, where to use and when to use, and most importantly: WHEN NOT TO USE!!!
I hope that helps to clarify my former posting for you.
Regards
Robert Olifent