Re-Bluing a tang questions

I have a few razors in various stages of resto that have the original tang bluing: Case Red Imp wedge, Dubl Duck Dwarf, Challenger Razor. I've removed the pivot pin and separated the blade from the scales on the Challenger so far. I'm going to have to lose the bluing to clean the entire blade thoroughly before it goes in the tumbler with corn cob medium.

I've seen some attempts at re-bluing that seem decent but not uniformly dark (pics may not have done the work justice and I can't even remember when I saw such pics).

Is there a good way to be able to mask the areas of the blade that I DON'T want bluing on if I decide to re-blue the tang? I don't want the spine or the hollows blued and I don't want bluing to bleed into those areas. Any recommendations for ensuring a crisp clean edge between the blue steel and non-blued? BTW, I've never used bluing before but would research this on the net.

Thanks!

Chris L

I haven't used bluing in geez 15 years? But I was looking at a couple of razors with it and thought the blue area was dull, like not highly polished. If the blue area was say bead blasted before bluing it would have greater contrast with the high polished/white areas. as far as a resist I'm not sure but until the gun guys post...you might try anything that resits alcohol and try putting it on with a rag thats not dripping with the chemical just dampened. Oh, nail polish might work I use it while plating...a wax may work. There is a resist that is basically tar , the name of which evades me at the moment....

I reblue tangs frequently. I use cold bluing. I do the metal prep just as I did for gun parts. I get very clean edges because the steel is prepped correctly. It must be absolutely clean before bluing or you get the different shades.