Many people define white as the absence of color. In the case of white carpet, this is not necessarily true. White carpets are not created by the removal of colors and pigments; they are dyed white. Bleaching a carpet eliminates or reduces its current color, but the result is generally some shade of a beige, tan or buff. Once lightened, floor coverings can be easily dyed any color, including white. Washing rugs in standard-issue chlorine bleach is the time-honored, traditional way to remove stains, discolorations and colorants from fabrics and materials. Chlorine can damage synthetic yarns, cotton fibers, wool threads and silk filaments, however. To prevent unintentional fiber damage, use a milder bleaching agent, such as hydrogen peroxide, to lighten carpets and rugs.
Sweep the rug to remove any loose dirt and then wash the carpet. Pour 1 tbsp. powdered laundry detergent into a large bucket and add 1 tbsp. soda ash and 5 gallons water. Stir the solution briskly and sponge it evenly over the rug. Wipe with plain water to rinse.
Pour 2 qt. lukewarm water into a plastic bucket. Stir in 1 tsp. powdered laundry detergent, ½ cup soda ash and 6 pints of 3 percent hydrogen peroxide.
Transfer a portion of the solution to a plastic squirt bottle and apply the peroxide solution to the carpet. Spray the carpet, refilling the bottle as needed, until all of the fibers are evenly moist. Allow the carpet to dry.
Mix 1 cup distilled white vinegar into 1 gallon water. Dip the bristles of a push broom into the solution and use the wet broom to sweep the carpet. The vinegar deactivates any lingering bleaching agents, and the brushing action perks up the fibers in the rug.
Inspect the rug and repeat the entire process, if necessary, until the carpet reaches the desired shade of off-white or tan. Then apply white fabric dye according to the package directions.