The simple answer is yes, you can dye a comforter, as long as it contains a fabric that can be dyed. Whether you're dyeing a new comforter or reviving an old one, the outer fabric cover is the target for color change. A patterned design on the fabric will not disappear with dye, but after dyeing it, it will achieve an interesting color shading over the original print. If your comforter doesn't have a removable fabric cover, you can dye the entire bedding cover, but you may need to use an extra-large capacity washing machine for a queen or king-sized bedding.
Know the Fiber Type
Check the label information to determine the fiber content of the fabric cover. Commonly available grocery store dyes are formulated to color most natural fibers, but art supply stores and craft shops may carry dyes that are made to work with specific types of fibers. Dyes for polyester work with some types of synthetics, but may not work for all -- experimentation is sometimes necessary. Natural fibers such as cotton, silk or linen result in bright, vivid dye jobs. Fiber blends such as cotton-poly tend to yield pastel rather than bright colors.
Comforters are typically filled with polyester fiber-fill or down -- the soft underlay feathers. Polyester fill doesn't readily accept dye, but down often does. In a nutshell, microscopic pigment particles suspended in water attach to the fabric fibers. Hot water or chemicals in the dye make the color particles bond with the fibers. For this reason, placing a feather down comforter in a dye bath requires more dye than a polyester-filled comforter because the feathers will accept part of the dye particles.
Washing Machine Dyeing
Use the Gentle or Delicate cycle on your washing machine to keep the comforter from bunching up. If it bunches up, the dye won't reach the areas between the folds. If you opt to dye your comforter at a laundromat with a extra-large capacity washer, check with the attendant before using dye in the machine.
Weigh the comforter to estimate the amount of dye you'll need. A twin-size comforter with a medium-weight outer fabric and medium loft polyester fiberfill weighs about 2 pounds. One full box of powder dye is required for each pound of fabric, while a full bottle of liquid dye can handle 2 pounds of fabric. Increasing the amount of dye improves color saturation without changing the hue. If you want a brilliantly deep color, use more dye to increase saturation; if less color saturation is desired use more water in the mixture.
Wash the comforter. Clean fabric accepts dye best; any type of fabric finish or residue coats the fibers and can prevent the dye particles from adhering. Pretreat spots and stains to remove them as much as possible. Stains are likely to ghost through even a dark color dye. Remove the wet comforter from the machine and set it aside.
Fill the washing machine with hot water and set it for the largest load size. Commonly available dyes work best if there is plenty of room for the item to move freely in the water. Preset the cycle to run two rinse cycles, if possible.
Shake liquid dye well and pour it into the washing machine. Dissolve one package of powdered dye in 1 pint of hot water for every pound of fabric before adding it to the washing machine. An average twin-sized comforter requires 2 boxes of powdered dye dissolved in 2 pints of hot water before adding it to the washing machine water.
Dissolve 1 cup of salt in 4 cups of water and add it to the washing machine with the dye to help set the color in natural fiber comforters such as cotton or linen. For silk or nylon, pour 1 cup of white vinegar directly into the washing machine with the dye to help set the color.
Add the clean, wet comforter to the washing machine. Close the lid and let the cycle proceed. The length of time the comforter is in the dye affects the color. You can increase the color intensity by pausing the cycle before the dye tub drains and reset it for another wash cycle. The comforter should be in the dye for at least 30 minutes for best results.
Allow the cycle to finish. Set at least two rinse cycles to ensure that all stray dye particles have been removed.
Wash the comforter with regular laundry detergent in warm water and a cold rinse after dyeing.
Dry the comforter in a dryer or hang it to dry out of direct sunlight to prevent fading, depending on the production instructions.
Clean the washing machine by filling it full of hot water with 1 to 2 cups of bleach added. Wipe inside the machine wherever dye may have splashed, and pour some bleach solution through dispensers inside the machine. Place some old towels or rags in the machine and let it run at least one full cycle.