Hot Bluing Advice

Pittknife

Pittknife

Joined
Oct 1, 2013
Messages
901
Hi Guys,

I need to brown or blue some damascus for a new project and am looking to build a salt bath system. I've done research and am confused on if I need a black iron pot or stainless steel pot? I'm only doing blades up to 8" so I don't need a big system. Just something I can put the blades in to get the colors.

If anyone has links or suggestions please let me know, I would greatly appreciate it.
 
Stainless steel tank for parkerizing.

Carbon steel tank for blueing. Brownell's calls theirs "black iron" which may be part of the confusion.

I would not use an aluminum turkey fryer pot for anything but frying birds.
 
Hot blueing is the exact same thing as (true) black oxide. You'll probably find all the info you need if you search for 'black oxide equipment' or a similar query.

Some links:

http://www.finishing.com/0200-0399/204.shtml
"Since the tanks can be built of plain steel and 'a tank is a tank is a tank', there is clearly a temptation to build your own tanks. But because water boils at 212, it can 'flash' to steam if introduced improperly, which can result in a blowup or eruption of the tank contents, splashing people with boiling hot caustic! For this reason, the operation is rather dangerous and I wouldn't advocate building your own tank just to save a few dollars, but only if there is a really good reason and you were willing to do a lot of research into the details."


https://www.birchwoodtechnologies.com/Process-Equipment/BK-TT-Mini-Tru-Temp-Line.html

http://www.dulite.com/ -- used stainless tanks here http://www.dulite.com/dulite_used_equipment.html
 
Salt pot "bluing" is simply heat-coloring the blade. It's not the same as gun hot-bluing.
Heat coloring will detemper the blade to spring hardness-somewhere around 50 RC.
Heat coloring can be done with a torch if you are very careful.
 
Bill DeShivs said:
Salt pot "bluing" is simply heat-coloring the blade. It's not the same as gun hot-bluing.
Heat coloring will detemper the blade to spring hardness-somewhere around 50 RC.
Heat coloring can be done with a torch if you are very careful.
Click to expand...

I'm googling the term "salt pot bluing" and it looks like it is used to describe both processes.

Here are some DIY true bluing/blacking "salt-pot" systems:
http://www.blindhogg.com/homemadesalts.html
http://www.guntechtips.com/bluing/bluing.htm
 
Made my tanks back in my gunsmithing days. Used 16 gauge steel if I remember right,been a while. Have a gallon of vinegar on hand to wash off with. The bluing salts have a very high pH and the evaporating liquids make your skin itch/burn but the vinegar rinse neutralizes it instantly. Copper is an enemy of bluing salts so no copper coated wire for welding.
 
For true bluing like on a firearm, I used home made carbon steel tanks. The salts can attack aluminum. Don't use an aluminum turkey pot. Parkerize bath was stainless homemade. Under these I had pipes ran from a propane bottle and regulator. Cleaning tanks where a soap tank (heated) and a water tank (heated)

I actually had a small bath I would do on a kitchen stove top set up outside and did it in ammo can for small jobs like parts or pistols lol.

I would start a refinish by removing old bluing with weak sulfuric acid in a tub set up. Wipe it down. Then refinish the metal to whatever finish the customer wanted. Head out and heat everything up. Rinse it well in the tub. Run it through heated soap water. Rinse well in tub. Heated clean water (i sometimes would bake before but with no joints, a knife shouldn't need that), then straight to blueing tank. I don't remember times and temps, sorry. Was 20+ years ago. Out of blueing tanks to the bathtub for a scrub and rinse then straight to oil, usually spray wd40 cause it was quick. After that I would apply a better oil and let it sit for awhile. Sometimes the salts would leech out of fittings (like Barrel to action joint) but you shouldn't have that problem.

Getting all oils out is the ticket. You get all oils out and get that metal clean clean and your hot salt bluing should come out stunning.
 
The process for hot bluing a damascus blade: 15 min in metal cleaner, rinse in cold water, 20 to 30 minutes in bluing salts, depending on desired color. Longer for black, shorter for blue. Salts are kept at 292 FH. while bluing is taking place. Rinse in cold water and inspect for flaws. Place in boiling hot water for 15 min, move from hot water to water displacing oil in one motion, it wants to go into the oil when the piece is at 200+. Leave in oil for several hours. Sand the surface with 2000 grit paper on a block to bring out the highlights or leave totally black, both are nice.
Mild steel pans along with mild steel wire is all you want to use around the salts, other than a skimming screen and dipper to add water, which should be SS.

You can print off a copy of Brownell's process for hot bluing on line. Its very helpful.

The top blade is hot blued thirty minutes without the surface being sanded. The second blade is hot blued for thirty minutes and the surface sanded using 2000 grit sand paper.

Sp9LAaXKfUPypCQvQivwtLNiZconuihasdNZvVbLfgYQe2HjqfH7XjFWTXYrxez0mXH-qU32n5SXRg=w1366-h768-rw-no

rzb4byxEefSpqmFJKfAJBdqA5qRmwJ5ZLXe3B4BTLVC6Ey_iNupQm3s0QYCeLIUDUS7qI4kSKEAtow=w1366-h768-rw-no
 
There ya go. Mr fred knows what he's talking about and sounds like he's done it alot more recently than I have.
 
Thanks guys I really appreciate it. I read the Brownells and looked at their system but did not want to spend $2500.
The turkey fryer was for the burner system and portability. I was going to use a steel pot but now will but one with enamel.

Thanks again, really appreciate all the help
 
A turkey fryer burner and steel pot would work. But make sure you have good temp control and enough volume so when you drop the parts in the temp don't drop too bad. Temp control is very important. Notice fred said 292 deg f. That's pretty precise.
 
SVTFreak said:
A turkey fryer burner and steel pot would work. But make sure you have good temp control and enough volume so when you drop the parts in the temp don't drop too bad. Temp control is very important. Notice fred said 292 deg f. That's pretty precise.
Click to expand...

Thanks man, I was thinking about a 4 gallon pot. My blades are not big as I make folders. I am concerned with tenp but I think this setup for u see $200 should work for a trial run.
 
The four gallon pot should work fine. The temp. control and clean blade before submersion is the key to success.
If it fails you can give me a yell. I run blades pretty often.

Good luck, Fred
 
I was referring to using molten salt to color steel, not using bluing salts.
 
Bill DeShivs said:
I was referring to using molten salt to color steel, not using bluing salts.
Click to expand...

Understood. However, the internet community seems to mix up the two processes and uses the term "salt pot" to describe both.

To clarify what Bill is saying, there are two distinct processes that both use hot "salts":

1 - Heat coloring, using molten salt as a thermal-transfer medium. In this process, the salt is not reactive and people apparently do use aluminum containers. The salt is not mixed with water. Temperatures exceed 400°F and will affect heat-treatment as Bill mentioned. The process is outlined here https://www.reddit.com/r/guns/comments/2bgcvd/diy_home_reblue_stepbystep_nitre_blue_in_your/

2 - Reactive coloring, using caustic chemicals (mostly lye) - also known as hot/true black oxide or hot/true bluing. In this process, the salt reacts with the steel to convert surface iron to magnetite. The chemicals are mixed with water and temperatures do not exceed 300°F. The process is outlined in links I've posted above.
 
Fred.Rowe said:
The four gallon pot should work fine. The temp. control and clean blade before submersion is the key to success.
If it fails you can give me a yell. I run blades pretty often.

Good luck, Fred
Click to expand...

Hi Fred,

What part of Ohio you near? I'm in Pittsburgh and would love to see it done or your setup?
 
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