Things You'll Need
100 g skeins, white 100 percent wool yarn
Mild wool wash
Fluorescent acid dye
6 qt. stock pot
Making yarn glow in the dark is a challenge even for yarn manufacturers, because most glow-in-the-dark additives are pigments that are painted on. Painted-on glow-in-the-dark pigments harden fibers and flake or wash off easily, so these paints are not useful to color and spin yarn fibers. However, there are some fluorescent dyes and brighteners available that will dye animal fibers in a bright color that also glows under a black light.
Wind each skein of white wool yarn into a loose skein by holding the end of the yarn in one hand with your arm bent up. Then with the other hand wind the yarn down around the bent elbow and back up around between the thumb and fingers. Keep winding like rolling up a cord or rope.
Tie the coiled skein loops with a few 4- to 5-inch pieces of scrap yarn to keep the skein from unwinding or tangling.
Fill a sink with water at 100 degrees Fahrenheit and check with an instant thermometer to ensure an accurate temperature. Next, add 1 tbsp. mild wool wash to the warm water. Place enough yarn skeins to complete your project into the water and soak for 10 to 15 minutes.
Fill the stockpot with water and bring it to under a boil at 180 degrees Fahrenheit, checking the temperature with an instant thermometer. Put on a dust mask. Add 1 tsp. of fluorescent acid dye and 3 tbsp. of vinegar to the water for every 100 g skein of yarn being dyed.
Drain the sink and rinse the yarn in warm water, squeezing gently to remove excess water. Place the yarn into the dye-bath solution in the stockpot. Slowly stir the yarn in the dye bath to make the yarn an even color.
Slowly bring the dye bath and yarn up to a simmer or 185 to 200 degrees Fahrenheit, but do not boil the dye bath or the yarn will felt or become matted. Simmer until the yarn takes up all the color and the water is clear, which will take up to 30 minutes.
Remove the dyed yarn and place it in a clean sink. Allow the yarn to cool until you can handle it and then rinse in warm, not cold, water -- about 100 degrees Fahrenheit. Squeeze out the excess moisture and hang the dyed skeins to air dry at room temperature.
Dye all the yarn for your project in one batch to keep the color consistent.
Use fluorescent paints on the knitted or crocheted project after it is done for more intense glow-in-the-dark effects.
Heat the wool yarn gradually and do not use cold water to wash or rinse the yarn to prevent felting or matting. Also avoid agitating the yarn as much as possible.
Use caution with acid dyes, especially when measuring the powder.
Do not re-use the equipment for dyeing in your kitchen because commercial acid dyes are toxic.