Fleece of any type can be dyed as long as you use the correct type of dye. If you attempt to dye polyester fleece with dye made for cotton fabric, the dye won't stick and will rinse out of the fleece. Fleece fabric comes in several varieties, including wool and polyester. You can also dye wool fleece direct from the sheep. Fleece can be dyed in your home washing machine with minimal trouble. Once dyed, the new color will be permanent.
How to Dye Fleece
The easiest and cleanest way to dye fleece is in your home washing machine. Fill the machine with hot water and add the dye. Immerse the fleece and soak for the time indicated by the dye manufacturer (usually 30 to 45 minutes). Rinse and remove the fleece, then line dry. You can dye multiple pieces of fleece at the same time or add other fabric items to the dye bath if desired.
Polyester fleece is made from synthetic fibers and can only be dyed with fabric or textile dye specifically formulated to work with synthetic fabric. Look on the label of the dye you are considering and confirm that polyester or nylon is one of the included fabrics. If a dye will work on nylon, it will work on polyester. The dye that comes in a tie-dye set is formulated for cotton fabrics and will not work on synthetic fleece.
Wool fleece can be dyed with any type of dye, including tie dye formulations, Easter egg dye and food coloring. While wool fleece can be dyed in the washing machine, it needs to soak undisturbed and then be rinsed and spun to remove the water. Never agitate wool fleece; it could damage the fabric.
If a fleece fabric has a printed pattern on it prior to dyeing, the pattern will remain, it will just be a darker or brighter version of the original. No matter what type of fleece you dye, choose a new color that is darker than the original; you can dye yellow fleece black, but yellow dye will have no effect of black fleece. You can use your dyed fleece as soon as it has dried, or store it until you are ready to use. No special care is required.