It's slow rust blue. Here's the info I typed up for another forum:
This is the fourth or fifth one that I've done. I'm far from an expert on the process, but I'm learning more as I go along. For what it's worth, here's my two cents:
I use Laurel Mountain Barrel Brown and Degreaser and follow the instructions on their site. Make sure you do the Blue step (scalding after each rust cycle and before carding.) You can order it from Midway or Brownells. I haven't tried other solutions. That's the first one I tried and it works well for me. A 2-1/2 oz bottle is sufficient for two K frames in my experience.
I sand with 320, then 400 grit wet/dry sandpaper. Use a small block when sanding the flat surfaces. (I use 1/2 inch wide on each side and 2 1/2 inches long.) Others use quarter-round. I use my fingers for backing when sanding the curved areas. I used 3-in-one oil generously when sanding.
There is no need to go beyond 400 grit. Slow rust blue is more of a matte finish regardless of how fine you sand the surface.
After done sanding, strip the blue. This can be done by soaking for a few hours in a 50/50 mix of white vinegar & water. I use naval jelly because it only takes about 10 minutes. It's nasty stuff and does etch the metal a bit. This etching requires another quick pass with the 400 grit.
You can do the rust by hanging the parts over a bathtub with some warm water in it. I eventually found an old veggie steamer at a thrift store. (Kind of like this one.) I built a 3.5'x2.5'x3' wood box and put the bottom portion of the veggie steamer in it. This cuts each rusting from hours to about 20-40 minutes.
I used warm water and pieces of old blue jeans to do the carding the first time I did this. It works, but is slow, messy, and leaves a duller finish. For my second revolver, I used a carding brush. A good carding brush gives a lot better results. I now use a carding wheel chucked into my drill press. This is much easier to use and provides superior results.
I prefer to do 5 to 7 cycles of the rust/card process. It looks decent after about 3.
After you are done with the process, let all of the refinished parts soak in a water displacing oil. I use Boiled Linseed Oil. If you use BLO make sure you wipe it clean before the oil dries.
BIG TIP:
The instructions say to do the last boil in water and baking soda, then card it one last time. On my most recent refinish, I did the last scalding in distilled water, carded, then boiled in water & baking soda. I then cleaned the revolver with and didn't card it again. If you card the gun after boiling in baking soda and water MAKE SURE THAT YOU GET ALL OF THE BAKING SODA OFF BEFORE YOUR FINAL CARDING. I missed some around the barrel pin the right side when doing my first one. You can see where this wiped out the finish during carding.
Don't use your wife's nice stove pot for the scalding. Find an old one at a garage sale or thrift store.
My first refinish was my grandmother's old Rossi 68. (Smith & Wesson Model 36 clone.) Here's some pics from the process:
Rossi 68 Slow Rust Blue
IANAL, or a gunsmith, so use your own best judgement.
Oh yeah - before pictures:
