Things You'll Need
Instructions
Wash the canvas according to your dye's pre-wash instructions. In most cases this will require you to wash the canvas in warm water and laundry detergent.
Put on a pair of plastic gloves. Mix the dye while the canvas is washing so that it is ready to use when the wash cycle is finished. Mix your dye in a plastic container that you do not mind being stained. Clean plastic soda bottles work well. Use a funnel to pour the dye into the container if needed. Add the correct amount of salt and water according to the dye's package instructions. It will vary between brands. Place the lid on the container and shake well until the dye and salt are fully dissolved.
Adjust the washing machine to its warm/cold setting. The canvas sheet should remain in the machine from its first washing. Allow the machine to fill with water and pour in the dye mixture. After the machine is finished with the first agitation cycle, reset it to run a second one. Do not allow the machine to rinse or spin between agitation cycles. After the two cycles, allow the machine to finish an entire wash cycle, including a rinse and spin.
Remove the canvas from the washer. Run a stream of cold water over one corner to check that all of the excess dye has been removed. If the water runs clear, dry the canvas and use. If the water is tinted, put the canvas back in the washing machine and run it through an additional cold rinse cycle before drying.