3%. HR source rock in front with powdered HR in center of plate. The chemicals and procedures involved with the following process are dangerous and can form toxic gasses. You should not attempt this process if you are unfamiliar with the safety procedures involved in working with these materials and procedures.he chemicals and procedures involved with the following process are dangerous and can form toxic gasses. You should not attempt this process if you are unfamiliar with the safety procedures involved in working with these materials and procedures.