Jun 22, 2014· Nitre Bluing is not the same as Hot Salts Bluing (although heat and salts are used). Nitre bluing is more closely related to heat treating or heat bluing. The parts are suspending in a salt solution that contains Potassium Nitrate, Sodium Nitrate and other chemicals (Brownell's recipe also contains Sodium Nitrite, other recipes include Manganese Dioxide) that is heated to 600 degrees.