The basic laundering operation is a physical-chemical process that utilizes four major factors which determine the quality of textiles being laundered. The four factors have become known as the detergent pie.
Time
Temperature
Mechanical Action
Chemical Action
The objective of these four components is to create the optimum cleaning conditions. Any decrease in one of these variables must be compensated for by an increase in at least one of the three remaining variables to prevent a reduction in wash quality. For example, a decrease in time can be compensated for with an increase in chemical concentration.
Time – This is a requirement for each step within the wash formula and is usually based entirely on factors that exist within the individual laundry. For example, A “suds bath” or “break” may average eight to ten minutes with a surfactant or solvent type detergent but may require twelve to fifteen minutes when utilizing an enzyme detergent. Other factors that directly affect time include water temperature, water conditions, and water level. Load size and soil classification can also affect time for a formula step.
Temperature – The ability to control the temperature of the water being introduced to the washer in any given step during the formula is a crucial element. The proper choice of temperature is driven by the composition of the fabric that is being processed. Temperature selection can also be driven by the step in the formula. For example: Rinses may start off at a higher temperature and end up at a lower temperature. Enzyme-based detergents usually can be less effective at higher temperatures than other types of detergents. When bleaching, temperature directly affects chlorine and oxygen differently. Other factors include linen classification, soil content and soil type.
Mechanical Action – This is the pounding action that the washer creates to remove embedded soil. There are several variables that directly affect the efficiency of this process. The most common throughout the industry is overloading. It also does not allow complete dispersion of the chemicals within the washer. Water levels may also affect mechanical action.
Chemical Action – This is the process of adding chemicals into the washer at specific times during the wash formula to assist in removing soil, discoloring stains, sanitizing and disinfecting, softening, and starching goods during each step of the formula. Chemicals are added directly to the wash wheel through different types of dispensing systems. Chemical selection is based on water conditions, goods being processed, and the laundry’s individual needs and goals.
Wash Formula or Wash Cycle
The wash formula or cycle is a proper balance using the four basic cleaning factors and will vary according to the degree and type of soil. Proper sorting and loading will help ensure that the cleaning factors-time, temperature. Mechanical action and chemical action are used to design a balanced washing formula.
The basic steps of a washing formula are:
Flush : (2-3 minutes) This step in the wash process is designed to prepare the laundry load for the washing procedure by loosening soil and heating up the load. Classifications and soil content will directly affect the time, temperature and chemicals required for this step in order to achieve optimal outcomes, though items are generally flushed at medium temperature and a high water level. The flush will break up and remove gross soils so that the subsequent steps are effective.
Break: (5-10 minutes) The term break is derived from the fact that it is at this point in the wash formula that the bulk of the soil is broken loose from the fabric and suspended in the washing solution with the help of a highly alkaline product that has been added at a medium temperature and low water levels. This is an optional step.
Suds: ( 5-8 minutes) The actual wash cycle is known as ‘suds’ when the articles are agitated in hot water and low water levels. The detergent is added at this suds stage.
Carryover Suds/Intermediate Rinse: (2-5 minutes) This step usually employs no chemicals but can remove or flush residual soils that were not removed during the break/suds. Its main function is to lower the soil and alkalinity concentration, usually prior to the bleaching step. It rinses linen at the same temperature as the suds step.
Bleach: (5-8 minutes) This step is used for whitening or to discolor stains. Bleach is added at high temperature and a low water level. Sodium Hypochlorite is the most commonly used. This step is also affected by time, temperature and mechanical action. For most operations, sanitizing and disinfection is accomplished here.
Rinse: (3-5 minutes) Once all the washing and bleaching is accomplished, we can now begin to rinse out and flush the chemicals and soils out of the goods. Typically this is a high water step and the temperature gradually decreases through each rinse. Rinses usually average around two minutes with up to three rinses per formula.
Intermediate Extract: (2-3 minutes) This is an optional high-speed spin that removes detergent and soil from the linen. It should not be used after the suds step to avoid driving the soil back into the fabric and also should not be used on no-iron fabrics except at lower temperatures.
Sour or Softener: (3-5 minutes) Often called a “finish step,” the softener and/or sour is added to this step to condition the goods for removal. The chemicals added here will directly affect the quality of the goods after being processed. Starch/sizing replaces the sour/softener step when cotton or polyester items need to be stiffened. This cycle runs at medium temperature and low water levels.
Extract: (2-12 minutes) This removes excess moisture from laundered items through a high speed spin prior to drying. The length of the spin depends on various factors such as fabric type, extract speed etc. This step is also important to reduce the weight of the linen for ease of movement to the dryers.