butyl agents. The amount of time the pretreatment dwells in the carpet should be less than 15 minutes, due to the thorough carpet brushing common to these "very low moisture" systems, which provides added agitation to ensure the pretreatment works fully through the carpet. The benefit of dry carpet cleaning, over wet solutions, is that dry chemical compounds do not attract dirt, like dried shampoo. While dry carpet cleaning is more expensive and more time consuming to clean than bonnet or extraction, dry cleaning formulas put less stress on the carpets themselves. Dry compound A 98% biodegradable or other, slightly moist absorbent cleaning compound may be spread evenly over carpet and brushed or scrubbed in. For small areas, a household hand brush can work such a compound into carpet pile; working like "tiny sponges", the attracted cleaning solution dissolves dirt, and dirt and grime is attracted/absorbed to the compound. After a short drying time (the cleaning solution which is attracted to the compound must evaporate), it will be removed with a vacuum cleaner, the drier the better, leaving carpet immediately clean and dry. However, it is very difficult to remove all residues. The residues can cause allergies and biological compounds may cause discolourations on carpets. For commercial applications, a specially designed cylindrical counter-rotating brushing system is used, without a vacuum cleaner. Machine scrubbing is more typical, in that hand scrubbing generally cleans only the top third of carpet. Encapsulation In the 1990s, new polymers began literally encapsulating (crystallizing) soil particles into dry residues on contact. In the conventional cleaning process surfactant molecules attach themselves to oily soil particles, suspending them (emulsification) so that they can be easily rinsed away. Surfactant (detergent) molecules and emulsified soils which escape being rinsed away, remain in the fibre and continue to attract soiling. Encapsulators are specialty detergent polymers which become part of the detergent system. As drying occurs (20-30 min. drytime), after cleaning, these encapsulators bind the detergent molecules and residual soils in a brittle, crystalline structure. Detergent and soil particles can no longer attract other soils and are easily removed by dry vacuuming. In addition to binding the detergent and soil residues the encapsulation chemistry coats the clean fibre with the same brittle film. This reduces the fibre’s affinity for oily and particulate soils. As this brittle film "breaks away" and more soil is removed, the appearance of the fibre improves as opposed