I have now tried 3 commercially available rust bluing solutions--Pilkingtons, Brownells and Laurel Mountain Forge--for standard rust bluing. I polish to 320 at least, sometimes to 400, never beyond that. I boil for 12-15 minutes in distilled water (stainless steel tank). I do the first rust for an hour, then recoat, rust for another hour. Other rustings about 1 1/2 hrs.
I find Pilkingtons easiest to use, most consistent and best results.
Next I think I like the Laurel Mountain Forge. I have tended to use it when I am having a problem getting a particular area to blue correctly but I may use it more in the future as a general bluing solution.
Last choice is Brownells. It leaves a less-than-perfect finish, sort of cheesy looking.
I am hoping there will be some others to chime in.
