Measure the stage area and find a suitably sized cotton sheet. Any kind of cotton is suitable, but muslin is the easiest to use. Make sure it is clean before you dye it.
Mix together warm water and the fabric dye is a large container. Mix the dye with a little warm water using a spoon or cocktail stick to create a paste, then add 1 tablespoon of this for every 3 gallons of water. Combine red and brown dyes to create a base brick color. Add a little extra dye to create a darker reddish brown.
Add 3 cups of salt for every 3 gallons of water, mix together and fully submerge the fabric in the dyeing liquid. Let stand for 20 minutes, stirring occasionally with a wooden stick or paddle.
Gradually add 1/3 cup of soda ash to the mixture over a period of 15 minutes. Make sure the cloth does not come into direct contact with the soda ash by pushing it to one side of the container with the paddle when you add the ash.
Remove the cloth from the dyeing liquid, rinse with cold water to remove excess dye and leave to dry naturally.
Paint the mortar lines of the bricks on the dry fabric with a small paintbrush and some gray or beige paint. Acrylic paints are the best to use here.