If you are going to use the grounds you probably should use a seperate container so that you can pour them off when the dye bath is complete. If you are just looking for the cofee color I would use the brew and pitch the grounds Or you could spread preapared fabric out on a plastic covered table , smear the coffee grounds around on the fabric and let it dry then either shake them off outside or run it throught the washing machine with synthrapol or some other fixing agent. Good luck!!!!!!!!!