If you’re to match the color of something, or if you’re no longer happy with the color of that cotton shirt, you can use a fabric dye to change the color. To ensure that the color sets into the fabric, meaning that it doesn’t bleed out in a regular wash, you’ll need to follow some basic principles, while still following the manufacturer’s package instructions. Select a dye that is “fiber-reactive” which works best for cotton.
Prewash your fabric with synthrapol detergent, following manufacturer’s instructions, to ensure the cotton is clean. Synthrapol works as both a pre- and post-wash treatment for dyeing fabric. Use about 2 ounces of synthrapol in a full washing machine load.
Mix the dye ingredients with water, according to package instructions. Exact quantities will depend upon the amount of cotton fabric you intend to dye.
Immerse the fabric in the dye mixture until it reaches the appropriate color. Wring out excess dye back into the container.
Cover the fabric, or cover in plastic wrap and allow the fabric to set for 6 to 24 hours, depending upon how deep you want the color. Allow 6 hours for pastel colors and 12 to 24 hours for deeper shades.
Rinse the fabric in cold, running water.
Remove excess dye by laundering the fabric with a synthrapol detergent in hot water. Synthrapol helps remove the dye not chemically bonded to the fabric, ensuring that the cotton won’t bleed in the wash in future launderings.