When you need a pair of black trousers but do not want to buy a new pair, consider dyeing a pair that you already own. You can achieve a good result with plain-coloured, natural fibre trousers, especially those without stains. You can even dye an old pair of faded black trousers to make them look new again. If you try to dye striped or other patterned trousers black, remember that the pattern will still show through the fabric in varying shades of black.
Check the tag of your trousers for the fabric information. Fabric must contain at least 60% natural, washable fibre, such as cotton, wool or silk, in order to dye evenly, although fabric that is not 100% natural fibre will not attain full colour.
Fill a bucket or sink with three gallons hot water. Do not use a plastic or fibreglass sink, as the dye will stain.Water should be 60 degrees Celsius for darkest colour saturation.
Remove two cups of hot water from the bucket or sink with a measuring cup.
Stir the dye powder into the two cups of hot water until dissolved. RIT dye recommends using double the amount of dye recommended on the package to achieve the truest black.
Pour the dye into the bucket or sink of hot water, stirring to mix.
Add 1 tablespoon of washing powder to dye bath to increase the evenness of the dye and 1/2 cup of white vinegar to increase the intensity of the colour.
Soak trousers in hot water. (Resource 1)
Place trousers in dye bath.
Stir trousers constantly in dye bath for 10-30 minutes. Keep trousers in dye bath up to one hour for deepest colour results and to assure a "true" black result. Remember that trousers look darker when wet.
Rinse trousers in warm water, then cooler water until the water runs clear.
Wash trousers in washing machine with a mild washing powder in warm water with a cool rinse cycle.
Hang dry or place trousers in a dryer according to the fabric directions on the tag.