Homebrew bluing question

[BenKeith]

Bluing with ammonium Nitrate and Lye (sodium hydroxide). I've used this stuff many times years ago and never had a problem. Now I'm trying to blue a Leupold scope base I've modified to fit an action on a rifle I doing for my granddaughter but things are not working.

First time it blued but had a brown looking crust on it that didn't want to come off. I'm using a fish cooker pot so if figured maybe the salts were contaminated because they turned brown during the cook down. I add more water and used that batch to clean the pot. I made another batch and it cooked down very clear but this time the part didn't blue at all, just a thin redish brown rust looking finish.

Tired off buffing it out, I polished some scrap metal pieces to work with. Thought maybe the salts were too thin so I doubled the size of the batch but still not getting a good blue and had a crust on it. I've been keeping the temp approx 295, never letting it get below 290 or above 300. I tried one piece at a hotter 305 - 310 but still didn't work. I have not tried a second thremometer but this one was new.

The ammonium nitrate is the pure white beads @ 36-0-0
The lye is Rooto crystals of 100% lye (since you can't get RedDevil anymore). I got an MSDS on the Rooto lye and it shows it to be 100% with no other additives. It does say a blend but that seems to be a blend of flakes and crystals. I've tried to get the Roebic Heavy Duty Crystal Drain Opener that contains 100% Sodium Hydroxide to see if it made a difference but no one I tried could even order it.

I'm going to get some Potassium Nitrate (Stump Killer) and see it it works on this part but I still need a solution to my Lye mix problem becuase I have two rifles I want to blue.

 

[MColeman]

Investment cast parts sometimes don't blue well. That's why you would see some purple Rugers in the early guns.

Mixing lye and ammonia nitrate will really clear your sinuses, won't it?

 

[BenKeith]

I've tried a couple of different steels and none have worked so far. I tried a lower temp last night (280 degrees). I also found a 2# container of Roebics Lye and still no luck. I'm thinking maybe it's the new Ammonium nitrate, possibly the tracer elements they put in it so gonna get some Sodium nitrate and try that. If that don't work, I guess I'll try a different formula all together.

 

[BenKeith]

Well, I now probably have the most expensive Leupold scope base on the planet but it's finally blued. I tried the straight potassium nitrate bluing and that didn't work either.

I picked up a four pound bag of 16% Sodium Nitrate and tried that instead of the ammonium nitrate. Worked like a charm, 25 minutes at 285 degrees and it's the same color and shine as the rifle. All I can figure is the trace element in the 36% ammonium nitrate I'm using is interfearing with the process.