Wash a sheet of muslin to remove all dirt and grease that will affect the dying process. The size of the sheet depends on the size of the stage.
Fill a container with hot water. The container should be large enough so the muslin can be fully submerged.
Add 1 tbsp. of dye for every 3 gallons of water. Mix the dye with a little warm water to make a paste before adding it to the hot water. Add 3 cups of salt to the dying mixture as well.
Put the muslin in the dying mixture, and push down with a paddle so it is fully submerged. Leave it for 20 minutes so the dye can be absorbed. Move the muslin around the container with the paddle during this period to ensure even dying. The paddle can be any piece of spare wood or other material, because it only needs to be strong enough to move the material around. A garden cane would be suitable for this.
Mix in 1/3 cup of soda ash into the dying mixture, and leave for a further 15 minutes. Don't let the soda ash touch the muslin directly, so push the cloth to one side of the container with the paddle, then add the soda ash.
Remove the muslin from the dying mix, and rinse it with cool water so any unused dye is washed out. Then, leave it to drip dry.
Paint designs on the muslin using acrylic paints. For example, dye the muslin blue, then paint on white clouds or green mountains.