Observations and results
Did coarse, natural fabrics, such as linen or 100 percent cotton, become dyed the darkest shade? Did synthetic fabrics, such as polyester or rayon, remain nearly white? Did fabrics that were a blend of natural and synthetic fibers become noticeably dyed, but not quite as dark as fully natural fabrics?
Cotton and linen fibers are both natural fibers made from cellulose, a compound found in plant cell walls. Fiber-reactive dyes form permanent covalent chemical bonds with cellulose, making this dyeing process a relatively permanent one. Polyester, however, is a synthetic fiber that does not react with fiber-reactive dyes in this way and cannot be effectively dyed using them. For polyester to be successfully dyed a different category of dyes must be used—specifically dispersion dyes, and a great deal of heat has to be applied during the dyeing process. In this activity you probably saw that synthetic fabrics were not effectively dyed, remaining nearly white, whereas the natural fabrics dyed the darkest shade and the blend fabrics were not quite as dark as the natural fabric (depending on the percentage of natural and synthetic fibers in the fabric).
You can safely pour the extra soda ash solution down the drain, flushing with water. Do not use the measuring cup, measuring spoons, plastic container or glass jar for cooking or food afterward. Carefully rinse and then recycle the plastic sealable bag.
More to explore
Fiber-Reactive Dye Chemistry, from Dharma Trading Co.
About the Dyes, from Paula Burch's All About Hand Dyeing
How to Make the Boldest, Brightest Tie-Dye!, from Science Buddies
This activity brought to you in partnership with Science Buddies