Mine "always" come out uneven. That's what I like about them! Ever seen a single-action Colt with only one, nice, even, non-mixed color case hardening? (& folks pay a boatload of money for them)
The bottom line, to me anyway, is getting the blade very clean and a little warm..then...just add pickle juice! I stick the blade, up to the hilt in pickle, Spanish olive, etc. juice and check it every few minutes. Usually you'll see the results you want. An earlier post (I think by Steve) showed a more consistent coverage with 100% vinegar. yeah? OK...whatever. Mine works and that's all I care about.
Good luck, Capt. Chris