Dyeing a shirt gray may seem like a tricky process, because you need to use black dye in a certain way to get gray. It is actually a fairly simple process to dye a fabric, such as a plain white cotton T-shirt to a shade of gray. You essentially need to just use less black dye depending on what shade you want. Follow a few steps to dye your fabric in just the right shade of gray you're looking for.
Step 1
Weigh your shirt on a kitchen or postal scale.
Step 2
Machine wash the shirt on the "hot" setting, which serves to scour the fabric.
Step 3
Put on the rubber gloves and an apron or old clothes.
Step 4
Use 1 tsp. of black dye powder for each pound of fabric for a pale shade, 3 tsp. for a medium shade, 6 tsp. for a dark shade and 12 tsp. for dark black. Dissolve the dye in two cups of room temperature water per pound of fabric and set aside.
Step 5
Prepare the dye bath in the bucket, adding 2 1/2 gallons of room temperature water per pound, along with 1 lb. of salt for light gray, 1 1/2 lbs. of salt for medium and 2 lbs. for dark. Add the dissolved dye and stir some more.
Step 6
Add the fabric and stir continuously for 10 to 15 minutes.
Step 7
Dissolve 5 tbsp. of dye activator for light and medium gray fabric, and 7 tbsp. for dark gray, in two cups of warm water.
Step 8
Remove the fabric from the bucket and pour in the dye activator. Stir it a little and put the fabric back in the bath. Stir continuously for five minutes and then stir every five minutes for the next hour.
Step 9
Remove the fabric and rinse thoroughly in a bucket of room temperature water, changing the water three or four times.
Step 10
Wash the fabric in hot water along with 1/2 tsp. of synthrapol per pound of fabric. Do this twice if you are going for a dark gray. Rinse with water and repeat the process until the rinse water is clear.