Need assistance on brass patina failures

We patina brass lamp parts brown using Surfin chemicals designed for that purpose. We are having problems with the patina failing (falling off, not stopping, oxidizing?) somewhat randomly, sometimes after a day, sometimes a week later. Seems worse on the darker browns. Worse on tubing, particularly square tubing, not a problem on cast pieces. May be related to quality of brass? Have tried other manufacturer's products, with the same problems showing up. Have tried many cleaning solutions (brass is buffed just prior to patinating). Sometimes we see the oxidation patterns on the brass parts before patina if they sit around a day or two. We often rebuff the parts and sometimes it takes ok. Very baffling, would love to hear from someone who might have any insight into our dilemma. Many thanks!

Do you use a buffing compound or buffing soap ?