"...I degrease all my wire wool in acetone. Leave them to soak for a while then take them out and let them dry naturally. I always thought thats enough but could be wrong..."
I think this may be the source of the problem afterall.
I've never been able to completely degrease steelwool,,not with acetone, lacquer thinner, hot soapy water & rinse or any combination.
( I guess you can buy degreased steel wool or stainless steel wool to avoid the problem,,I just never use the stuff to avoid the problems)
It may seem clear of grease after a good soaking in solvent (don't try burning it off!!), but a single speck in there somewhere rubbed out over the bbl when carding will coat the steel like you've purposely oiled it for putting up in the gun cabinet.
Certainly not what you want for rust bluing. Your water tank is then contaminated as are your soln container and applicator, ect from it. Even your gloves if you're wearing any.
Try carding a test piece with nothing more than a clean piece of canvas, denim cloth, burlap, ect. Even a piece of the fine scothbrite (white or maroon color). It might not be the most efficient but it'll at least tell you if you have color to the steel under the converted rust and it's staying put cycle after cycle. The converted blu/black fine coating should brush right off even with a swipe of the fingers leaving the color intact.
Worth a try, don't cost nuthin' to try..
A carding wheel then or in the least carding brushes if that's the problem.
