In addition to cotton and linen, any natural, unfinished material will absorb fiber-reactive dye, so experiment on bamboo, wicker, wood, and paper. You can soak the entire item for allover, consistent color, or just dip a portion for colorful contrast.
What you'll need (per pound of dry fabric):
Wash fabric with professional textile detergent, following manufacturer instructions. Combine soda ash and 3 gallons of warm water in a bucket, stirring until dissolved.
Submerge fabric in soda ash mixture. Do not overstuff; soak only fabric that easily fits in bucket. Allow fabric to soak in soda ash mixture for at least 30 minutes.
Combine urea powder and 1 cup warm water in a mixing cup. Pour a few tablespoons of urea mixture into a plastic mixing container with fiber-reactive dye in bottom. Work the powder and urea water into a smooth paste, then stir in the rest of the urea mixture to make a concentrate.
Add salt to 3 gallons of warm water in your dyeing tub, stirring until dissolved.
Add dye concentrate to saltwater and stir.
Wipe the inside of dye tub to prevent unwanted dye marks on fabric.
Wring out fabric and dip it in dye bath to desired point, carefully maintaining a straight dye line.
For deeper color, rest fabric over tub edge and let sit for 30 minutes or until desired color strength is reached.
With clean, gloved hands, remove fabric from dye bath.
Hold undyed end of fabric with one hand while wringing out excess dye with the other.
Rinse fabric with cold running water until water runs clear.
Wring fabric again, squeezing out as much excess water and dye as possible.
Wash fabric in hot water using professional textile detergent. If you're unable to wash immediately, lay fabric flat on clean plastic wrap and wrap completely to prevent unwanted dye marks and drying.