Once over and that's it w/LM. That should be the method w/most any cold rust solution, but a few seem to be able to take the scrubb method OK w/o any effects.
L/M doesn't and you'll get the copper plate effect a lot.
If I remember right,L/M doesn'thave any acid in it's ingredients. It's primary rust agent is Ferric Chloride. That's probably to the acidic side of the Ph scale though.
The copper sulfate was added as a 'marker' I recall reading in an article by John Bivins talking about the then reletively new L/M product and it's maker Rick Schreiber (sp?).
I'm no chemist and can't say why any of it works or not. But L/M does if you apply it right. It will work (rust) at very low temps,,like the 64F I keep the house at and what ever the wintertime humidity is in here.
But it's at least a 24hr+ rusting cyle at those numbers.
Hang the parts from the shower rod and close the door after a shower and they'll be rusted just right in about 1 to 2 hrs.
It's just rust after all. Technique is 90% of rustbluing IMO.
