Hot nitre bluing

[WobblyHand]

Been reading about this a bit and have decided to try this out. I'm only looking to blue small parts at the moment and don't want to get in too deep. So I bought a small Lee 4 lb melting pot for this project. As I understand it, the nitre is a mixture of 40% sodium nitrate and 60% potassium nitrate. I will use stump remover for the potassium nitrate. (99% KNO3) I picked up a couple of pounds the last time I visited my kids. I think I have some sodium nitrate around somewhere. If I don't, I think one can still get that in a garden store. I found a video by Larry Potterfield, showing the process. Since I'm not buying that awful tinted premade mix, perhaps I won't have as much junk to skim. (Skimming is not shown in the video.)

Using the PID controller , (the one I made for melting lead,) and a thermocouple probe with a stainless steel probe to close the loop. As I understand it, a temperature around 650F is needed.

Here are the instructions according to Brownell. https://feeds.brownells.com/userdocs/learn/Inst-362_Nitre_Bluing_Bluing.pdf

Hope to get the pot soon and blue a couple of small parts.

 

[GeneT45]

I'd be worried about using a "Lee Leaker" * for bluing. At the least I'd put an ample catch cup under the spout.
GsT

*Just a nickname, not really a knock on Lee - *all* the bottom-dispensing lead pots leak.

 

[WobblyHand]

I'd be worried about using a "Lee Leaker" * for bluing. At the least I'd put an ample catch cup under the spout.
GsT

*Just a nickname, not really a knock on Lee - *all* the bottom-dispensing lead pots leak.

Which is why I got a small pot with a solid bottom for this experiment.

My issue with a bottom pour was it would freeze up at lower molten lead temperatures, especially outdoors with any breezes. There was a high temp difference between the spout and the inside of the pot. To get it to pour, the lead had to be so hot it was oxidizing too rapidly. Finally plugged my bottom pour, removed the mechanism and now use a ladle. Casting got easier after that.

 

[xr650rRider]

You can do same thing with a propane torch. The nitre salts are just there for temperature control. Doesn't add anything to a bluing process. I use a torch and just as soon as blues develop, quench in used motor oil.

After you blue something in your pot, let it cool and I'll be you can rub the bluing off easily with some Scotchbrite.

 

[WobblyHand]

You can do same thing with a propane torch. The nitre salts are just there for temperature control. Doesn't add anything to a bluing process. I use a torch and just as soon as blues develop, quench in used motor oil.

After you blue something in your pot, let it cool and I'll be you can rub the bluing off easily with some Scotchbrite.

I know you can rub just about any bluing off with scotch bright. Most bluing is not meant to be a super protective coating.

Was hoping for something nicer than cold rust bluing with peroxide and salt. That seems to pit a little, and takes a while. (An hour, due to the many cycles.) It works, if you have the time. I've also tried commercial bluing preparations in little bottles and have failed to be impressed.

We'll see how this works. There's something to be said for a uniform temperature controlled bath. It's an experiment. If it works, fine. If not, onto plan B.

 

[WobblyHand]

Well the little melting pot arrived. Decided to look around the basement to see if I could find any NaNO3. I was somewhat surprised to find some, packed in a glass decanter with a ground glass stopper. The prills looked good, and were not sticking to each other, they "flowed" when the decanter was tilted. I'll do a quick sodium check to make sure it is sodium nitrate, but I'll almost positive it is.

I'll need to make a little clip for the thermocouple, so the TC will stay in the pot. Also need to find a cheap stainless spoon to use for skimming and stirring. Some better weather would help too, as it has been rainy today, and tomorrow is expected to be the same. This will be done outdoors at least for the first couple of times. I don't know what to expect, (not expecting any issues, but,) so it is safer to do this kind of thing outdoors.