Soil shielding

In detail

Soil is not only the thing being removed — while it is there it is also a shield. The trade specification that separates cleaning from disinfecting reports the CDC guideline that a surface be clean of soil and debris BEFORE it is sanitised or disinfected, and this is the mechanism behind that ordering. A disinfectant has to reach an organism to act on it. Grease, food residue and general grime physically cover organisms, and organic matter also consumes some agents chemically, so part of the dose is spent on the dirt rather than the target. Both effects point the same way: the dirtier the surface, the less agent arrives, and the less of it is still active when it does. The practical consequence is the surprising one. Spraying disinfectant onto a visibly dirty surface is not a partial success — it can fail twice, leaving the soil because a disinfectant is not a cleaner, and leaving organisms alive underneath it. Neither failure is visible afterwards, which is why the ordering has to be a rule rather than a judgement made at the time. It is also why contact time is quoted for a CLEAN surface.

Why

• Laminate flooring is explained by Soil shielding

  The answer to the sticky floor. A film-forming product leaves a layer that holds the next lot of soil, and on a melamine surface the bulletin says 'under no circumstances' about polish and beeswax.