Most carpet cleaning technicians have not done spot dyeing because they had difficulty getting the right color back into the carpet and making the dye colorfast.
Two electronic tools have improved the chances for success:
The reason these tools are of value is because the two problems in doing spot dyeing is color blindness and getting the pH right.
These tools overcome these issues.
Some degree of color blindness affects approximately 10 percent of men and one percent of women.
It rarely means one only sees gray; instead, the normal human eye sees in three hues:
This ability is due to a special cell-group behind the retina of each eye called “cone” cells, which are like radio receivers.
Red, green and blue represent three different radio frequencies.
When one cannot properly see one of these colors, the condition is known as Daltonism.
Even without this condition, most senses can grow numb after a while.
For many, this numbing effect happens in the final stages of spot dyeing, when the discernment is most critical.
Therefore, a better way of determining accurate primary colors is needed by everyone.
By the way, dogs have only two groups of cone cells; cats have three, but not our three; and birds and fish have four sets of cone cells.
This means all these animals see different hues alone the color spectrum.
Therefore, do not train your dog to do color repair.
Additive Color Theory
When red, green and blue lights are mixed together, they make white light.
This is why televisions sometimes have red, green and blue cables.
The theory on how this works is called the “additive color theory.”
In this theory, when red and green are equally mixed, it makes yellow; red and blue make magenta; and green and blue make cyan.
With many of today’s smart cellular phones, there are apps that can be downloaded that can calculate color based upon the additive theory for photographers.
Printers Color Theory
The additive theory does not work for pigments.
The additive dye theory will not work for printers and paint because it completely covers the surface.
The primary colors for this theory are cyan, magenta, yellow and black.
Subtractive Color Theory
Dyes work on the “subtractive color theory,” because they absorb some of the color from the additive theory.
What is seen, are the colors that are reflected back from a surface.
This is the theory used by textile dyers.
In this subtractive theory, red, yellow and blue are the primary colors.
When red and green are mixed it makes brown, which is a tertiary color.
Mixing all the colors in large equal amounts makes black.
Remember that in the additive theory all colors make white and black does not exist in that theory or the other theory.
This is why printer cartages come in cyan, magenta yellow and black.
The Color Meter
Smartphone app developers have now realized we need help too.
The problem is in converting RGB numerical values to RYB values.
Both Android and iPhones now sell apps that can do this.
With this latest development, now a color repair technician can make an electronic evaluation between a color loss and the surrounding yarns.
This means the phone can see the quantities of red, yellow and blue.
This eliminates the problems with color blindness and fatigue.
The pH Meter
The second problem in spot dyeing is in knowing what caused the problem and if it is still present.
Common household bleach, sodium hypochlorite, is the most common source for color loss in nylon.
If any of its residues are still present, it will compromise the integrity of the color repair.
Frequently, sodium hypochlorite is self neutralizing, but one can never be too sure.
If it has neutralized, the resulting pH will be around 5.5; if bleach is still active, then it needs to be neutralized with sodium metabisulfite to a pH between 6.7 and 7.3.
Most coffee and tea stain removers and browning treatments contain sodium metabisulfite which leaves a pH around 5.5.
Neutralizing Bleach Neutralizer
Applying too much sodium metabisulfite causes a problem too because it turns into sodium hydrosulfite with heat.
Sodium hydrosulfite destroys dyes.
Hence, reducing bleach can compromise spot dyeing too.
After applying bleach neutralizers, if the pH is around 5.5, it will need to be rinsed and neutralize to a pH between 6.7 and 7.3.
These pH readings can only be made by measuring the pH directly from the fiber.
The electronic pH meter is the only practical way of doing this.
Everyone can do color repair today.
All they need is a pH meter, a color-meter phone app and some dyes.
However, it is still recommended that one gets some training.
IICRC has a two day training seminar that can get you started.
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/jbsor call (972) 334-0533 or (800) 675-4003.