by Jim Smith

Did you know that the IICRC certification “Color Repair Technician” or “CRT” is a requirement to obtain your IICRC Master Textile Cleaner status?

Many have attended the class and have become certified, but only a few pursue it as an add-on service afterwards.

Why? The likely reason is due to color repair’s inherent difficulty.

First, one needs to know the reason for the color loss and then how to neutralize it. Then comes the challenge of getting the new dyes into the carpet.

In the past, this has been left to a gifted ability and luck. Technology can now replace the guess work with numerical values.

The cause

Color loss generally occurs from either reduction or oxidation. It can also occur from extremes in acidity or alkalinity. Reduction/oxidation can be related to acidity/alkalinity, but not always. Therefore, both should be checked.

Reduction/oxidation values

Reduction/oxidation can be determined with a REDOX meter. REDOX meters look very similar to pH meters. Typically, the meter’s range between negative 1,000 to positive 1,000 mv, (mv stands for millivolts). Negative numbers indicate reducers, while positive numbers indicate oxidizers. From minus 100 to positive 100 is close to neutral and is the goal in neutralizing. Minus 200 is common for most coffee/tea stain removers; positive 360 is common for 3 percent hydrogen peroxide. Red dye stain removers are generally minus 450 or less; household bleach and 12 percent hydrogen peroxide are positive 450. Meters can be off by 60 mv.


Acidity/alkalinity can be determined with a pH meter. Seven is neutral. Negative numbers indicate an acid, while positive numbers indicate an alkaline. In general, soiled carpet has a pH from 6.1 to 6.7. Most hot water extraction detergents leave the face yarn between 7.3 to 8.0. Most food and beverage related issues are between 3 and 6. A pH value under 3 indicates a strong acid; over 9 indicates a strong alkaline.


A chlorine meter is also very similar to a pH or REDOX meter except that it measures the element, chlorine, (Cl) in parts per million. Finding chlorine is important because it is found in household bleach and hydrochloric acid. [1]ORP values for chlorine by itself vary from 296 mv to 867 mv. A significant presence of chlorine with a very low pH is indicative of hydrochloric acid. Hydrochloric acid can damage the dye sites of nylon, making color repair more daunting… if not impossible.

Household bleach (sodium hypochlorite), on the other hand, will have high pH when it is fresh but is generally self-neutralizing to around pH 5.5. Having a chlorine meter is important because chlorine is the most chemically active element common to a color loss.

Colors and dyes

With pH and ORP values near their neutral point, the color can be reintroduced. Color repair technicians should be familiar with complimentary repair rules for tertiary hues.

  • Orange color loss needs blue dye
  • Green color loss needs red dye
  • Violet color loss needs yellow dye

While one may find themselves getting the color loss close to its original hue, there are limiting factors inherent in most technicians.

  • Color blindness where one does not properly detect some colors.
  • The sense of sight becomes fatigued.

The solution is to turn to a color meter that can measure red, yellow and blue. Whereas they have been cost-prohibitive in the past, smartphones have access to color meter apps that are very affordable. However, most color meters are based upon the photographer’s needs of red, green, and blue; dyes are based upon the RYB theory. Thus, the selection for apps with those features boils down to only a single selection for both Android or iPhones.

Using color meters

As with the chemical meters, relative comparison should be made of the problem area and the unaffected carpet. The format of how the primary hues are represented may vary.

Some apps may show color percentages based upon a total of 100 percent of all three primaries; others may show red, yellow and blue all able to reach 100 percent on their own. What numerical format the program uses is not important; the issue is which primary hue in the discoloration is most affected. For example, if the discoloration’s blue hue matches, and the red is over by two percent, but its yellow is under by six percent, the solution is to add yellow. On the other hand, if all the color values are too high, then a professional dye remover may be necessary.


Color repair need not be limited to a special few who are gifted. With a little professional training and the proper meters, almost anyone can repair color losses with ease.