I am experiencing something unusual during rust bluing barrels recently.
Rusting process as usual with diluted Laurel Mtn. Forge solution, and vertical steam chamber to convert to black oxide. Each iteration is carded like normal, and the barrels has an expected mirror black sheen. Barrels are coated with oil or grease to cure for 24 hours, and are hung in a low-humidity environment (inside the house with the a/c on). Go back to the barrels after 24 to wipe off the excess curing agent, to then polish breach face, etc. and I find the barrels have a gritty texture. The texture will wipe off, and is black due to oxide weeping from the pores (again, expected), but it's VERY black and abundant.
I know the curing location is dry, and the barrel is dry under the ribs, so I would expect that the reason is that the barrels were not carded well enough, or that there is an overabundance of black oxide that does not have a good purchase on the barrels: carding more would of course remove the abundance of oxide of course. I've been carding the same way I have over the last year, but have not had this problem before.
Further back I would card by hand with acetone soaked 000. Going back to that might be a step to reintroduce prior to curing.
Anyone seen this behavior? Solution you used to deal with it?