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Effective stain removal is one of the most challenging tasks a carpet cleaning technician will engage in — but, if done correctly, can also be one of the most lucrative.
Dye stains are the most difficult to remove. The process usually requires the use of chemicals called "bleaches." There are two different types of bleach which are opposites of one another.
1. Bleaches that remove oxygen called reducers
2. Bleaches that add oxygen called oxidizers.
Both need a chemical catalyst and energy to work better. Mild reducers and oxidizers are also used in detergents; strong ones are used only in spotters.
Reducers are best for removing acid or synthetic dyes, plus stains from coffee and tea.
Oxidizers can remove some of the same types of stains that reducers can remove, but in some cases with limited results. Oxidizers can eliminate both disperse and organic dyes.
The two common substances used for reducing bleaches are:
1. Sodium metabisulfite, a mild agent
2. Sodium hydrosulfite, a strong agent.
Catalysts are mild acids and the energy needed is "heat." The heat is generally obtained from an inexpensive clothes iron placed over a wet terry towel for a short period of time, typically less than 15 seconds per application.
Nearly all reducing bleaches give off foul odors, so ventilation is required for safety.
The two common substances used for oxygen bleaches are:
1. Sodium percarbonate
2. Hydrogen peroxide.
Sodium percarbonate has a built-in catalyst. The catalyst for hydrogen peroxide is ammonium hydroxide. The energy for both can be ultraviolet (UV) light. Remember that high heat can "set," or cause to be permanent, certain organic stains in the protein category.
Unlike reducers, oxidizers destroy odors, but can cause skin irritations. Gloves and eye goggles are necessary when working with strong hydrogen peroxide solutions. Opaque containers are needed for hydrogen peroxide solutions because UV light acts as a catalyst, which can cause bottles to expand and sometimes explode.
Oxygen bleaches destroy both disperse and organic dyes, plus acid and synthetic dyes. They also destroy other types of coffee stains unaffected by reducers, plus ink.
Disperse dyes dissolve in acetone or boiling water and are somewhat alkaline; therefore, applying a dry solvent first will help remove them.
Touch (feeling the texture) and pH readings are the best methods for distinguishing between dye stains, if the source is unknown.
The pH readings should be made with a digital pH meter.
Acid or synthetic dye has a pH between three and six and has no distinguishable texture.
Disperse dye has no contrasting hand (how it feels), but little contrast in pH.
Organic dye will likely have a crusty hand coming from the food component and a pH between three and six. The crusty residue should be removed before applying the oxidizer.
Peroxides and ultraviolet light
The science of peroxides and UV light is not new.
Other industries use it to destroy dyes, such as in "teeth whitening." The limiting factors in our industry have been the strength and frequency of the UV; however, that is beginning to change.
Recently, much stronger UV lights have become available. These kinds of lights can be effective for doing both inspections and stain removal.
Ultraviolet light can be several different bandwidths:
1. UV "A" band is best for inspections
2. UV "B" band is best for stain removal.
Some UV "A" band lights do have enough power to be effective for stain removal.
For inspections, UV light finds hidden evidence of urine and other bodily fluids. It can also find evidence of inappropriate detergents.
Cleaning products for carpet should not contain UV dyes because it interferes with acid dye blocker protectors. In addition, non-carpet cleaning products could be the reason for re-occurring spots or color loss.
Ultraviolet safety issues
Special eye protection is a must when using strong UV lights. It can cause severe damage to eyes. In some cases, the light can be reflected and cause unintended exposure.
The question is whether the market is ready for this technology. It will require a trained technician to work with high-power UV lights; however, desirable results could be seen in seconds. Low-powered lights are safer, but could take minutes to hours to work.
James (Jim) B. Smith is an IICRC-approved instructor and a senior practicing inspector. His educational studies come from Texas A&M University and the University of Houston. He has been in the cleaning industry since 1975. For more information, visit his website at www.carpetinspector.com/jbs or call (972)334-0533 or (800)675-4003.