An introduction to Facility Housekeeping

SOIL TYPES

To effectively remove soil from building surfaces, you need to understand the types of soil and the elements that make them up.  There are basically two types of soil: loose, dry soil and oily, sticky soil.  Each type requires a different process to remove it.  

• Organic (loose, dry) – Commonly referred to as dust.  It can usually be removed with direct mechanical action, as long as it stays dry.  It can be swept, dust mopped, wiped, vacuumed or wet mopped with little or no chemical action required.  Any surface that has not been cleaned in 12 hours will have dust accumulated on it.  The longer it remains on a surface, the better chance it has of becoming oily, sticky soil from contamination with other substances, even from moisture in the air or from air conditioning units.

• Inorganic (oily, sticky) – Soil or dirt is almost always mixed with grease or other oily materials.  Grease and oil make the dirt stick to a surface.  The longer dirt remains on a surface, the more it tends to bond to the surface and the harder it is to remove.  All grease and oil (animal, vegetable, mineral, or synthetic) have an oily nature due to hydrocarbons in their composition.  A hydrocarbon is a chemical compound of only two elements: hydrogen and carbon.  Hydrocarbons are what make grease and oil feel slippery and prevent them from mixing with water.

SOIL REMOVAL

The chemical processes by which a cleaning agent removes soil from hard surfaces, fabrics and skin are called DETERGENCY PROCESSES, and they involve a combination of chemical actions, including wetting action, emulsifying action, dispersing action, and adsorption action.

• Wetting Action – Water has a property called surface tension, which makes it act as though a skin were covering its surface.  It is this characteristic that makes water stand in drops on a dirty surface and prevents it from getting into and under the dirt on the surfaces you cleaning.  Cleaning agents incorporate chemicals that reduce the surface tension of water by making it wetter, so it can spread out evenly over the surface and get under the dirt.  This wetting action is necessary to remove dirt.

    SURFACE TENSION                           WETTING ACTION                                     

• Emulsifying Action – Water and oil are natural enemies that do not normally mix.  Soil is almost always made up of small bits of dirt held together by oil to form larger clumps of dirt.  Cleaning agents therefore, incorporate chemicals that help water break oil into small particles and then keep these particles suspended in the solution.

       EMULSIFICATION                       DISPERSING ACTION

• Dispersing Action – Once the emulsification process has separated the oil and dirt, other chemicals in the cleaning agents will break the dirt up into smaller particles and spread them away from each other to keep them apart.

• Adsorption Action – Cleaning agents include a chemical formulation that causes an attraction between particles of dirt and the cleaning agent itself, causing the dirt particles to stick to the cleaning agent. 

Other physical characteristics of cleaning agents that helps them to clean more effectively:

• Penetration – This characteristic determines how well a cleaning agent will get into the pores of a surface to loosen and remove all the dirt.

• Suspension – This characteristic enables a cleaning agent to hold dirt particles suspended in the cleaning solution and keep it from being redeposited on the clean surface.

• Viscosity – This is a measure of how fast or slowly a cleaning agent flows.  The thickest cleaners are like foam, which is useful for cleaning walls and other vertical surfaces.  

pH SCALE

The technical definition of pH is "the negative logarithm of the hydrogen ion concentration."  This definition, however, means little to the average person.  A more understandable way to express pH is in terms of "acidity", "alkalinity" and "neutrality."  pH is a measurement scale which ranges from 0 to 14 with 7 considered neutral.  Chemicals with a pH less than 7 are considered acids while those above 7 are considered alkalis (or bases).  Only chemicals that contain water or can be in a solution of water can be accurately tested for pH.  The pH scale is a logarithmic representation.  This means that each number, moving in either direction away from 7 (neutral), is 10-times stronger than the preceding number, but it is 10 times again as strong as neutral. 

Soils contain some degree of acidity or alkalinity.  To remove an acid-type soil, you use an alkaline-type cleaning agent.  To remove an alkaline-type soil, you use an acid cleaning agent.

PROPER DILUTION IS THE KEY