Home dyeing projects can result in amazing results, and fibre hobbyists typically choose natural fibres to dye since these yarns absorb and hold onto dyes better than synthetic fibres, such as acrylic. It is possible to dye acrylic fleece, but the results are typically light to medium in colour intensity. The process is also more difficult than dyeing natural fabrics, and only a few manufacturers create the special dyes for the fabric.
The dyes used for acrylic and polyester yarn or fabric are called disperse dyes. Dyes used for wool and nylon products contain acids to set the colour, and fibre-reactive dyes can colour cotton and rayon. At the molecular level, disperse dyes contain tiny, microscopic particles in water that attach to the fibres in polyester and acrylic fabrics. The dyes need agitation to slide into the chemical chains of the products made in the polyester family, as well as heat.
To change the colour of an acrylic fleece, thoroughly clean the fleece by washing it in water warmer than 60 degrees Celsius -- either in the washing machine or in a nonreactive pot on the stove, adding soda ash and a proprietary powder that removes all the dirt, sizing and oils from the fabric. Sizing is a starch used to manufacture fabric. The last cleaning step involves rinsing the fabric thoroughly to remove all of the residue from the fleece.
After mixing the dye with boiling water, strain and cool it before adding it to a nonreactive pot of warm water. Mix in and stir vinegar or citric acid; the mixture and then the fabric should go inside the pot. Heat the mix slowly, bringing it to a boil over the course of 30 or 40 minutes, stirring the pot constantly. Another hour of stirring intermittently keeps the fabric dye from settling into creases or folds, which results in an even distribution of colour. Remove the pot from the heat and cool it to 65.6 degrees Celsius. Run cold water into it to rinse the fabric. Once the colours drain clearly, remove the fabric, squeeze the excess water from it and dry it in the dryer.
Disperse dyeing involves standing over a boiling pot for a long time, which could result in burns. Any powdered dye is hazardous to the respiratory tract, and experts recommend wearing a dust mask while mixing the dye in water. Some people develop skin allergies to fleece dyed with dispersant dye products. No safety standards have been developed for using pots after using disperse dyes, so the pot should not be used for food preparation or cooking after being used for dyeing acrylic or other polyester products.