Charcoal blue

[WadePatton]

600 to 800 degrees, Fahrenheit or Celsius?

Best regards
Rolf

Old Money.  

I'm sure you know the conversion factor if you use that new funny money.


So it finally hit me that I have this unending supply source of "representative" material (round bar stock in 12L14, multiple diameters).

And with such, and the unlimited supply of pit and wood I have (free as well), that it'd be downright silly not to test fire a few dozen pieces in order to work up my "recipe".  I find it rare to have this opportunity of extremely low cost materials for testing and development of a process.  It shan't be wasted.

this is gunna be funna.  

[Joe S]

600 to 800 degrees, Fahrenheit or Celsius?

Fahrenheit

[Curtis]

Jerry,
 
The next time I do my charcoal bluing in a pipe, and in a pit, I will post some photos to see if I get different results from my previous posting, I like the results I obtained but it would be great to get even more consistent results.

Curtis

[davec2]

I love the smell of a wood fire as much as the next guy, but if you want consistent results with our a lot of trouble and expense, put the barrel in a black iron pipe with clean charcoal, as Jerry explains, and then use one of these wrapped around the pipe to get and keep a constant temperature for as long as it takes to get the blue you want.....

http://www.mcmaster.com/#heat-cable/=tzintq

With a single thermocouple and a temp controller you can find on e-bay for $40, you can precisely control the temperature up to the limit of the tape (~1400 degrees F).  The more precisely you can control any process, the more consistent the results.  Personally, I don't like risking a lot of hard work and parts to a process that requires the waving of chicken bones in a brown paper sack over my head on a moonless night.

[Jim Kibler]

That is a great idea, Dave.  Thanks!  Do you think the pipe and heat tape would need to be wrapped in any insulating material in order to get to temperature?

[firelock-inc]

I am planning on doing a 48 inch barrel.

Do in need 50 inches of pipe, and may be 4 inches in Diameter?

Any thoughts would be helpful.


Rickp

[WadePatton]

I love the smell of a wood fire as much as the next guy, but if you want consistent results ...  Personally, I don't like risking a lot of hard work and parts to a process that requires the waving of chicken bones in a brown paper sack over my head on a moonless night.

In my case, there is no desire for a perfect pretty blue.  Much more interested in an imperfect blue.  Seems as we've now hit upon a good way to attempt either sort of bluing.  Something for everybody! 

brown paper sack eh...I better get me some of those too. 

voodoo blue!

[WadePatton]

I am planning on doing a 48 inch barrel.

Do in need 50 inches of pipe, and may be 4 inches in Diameter?

methinks it's simply a matter of how careful you care to be whilst packing and how much charcoal you care to use.  A 2" inside diameter pipe should hold your bbl, but packing might be a chore.  Using a controlled heat source, I'd think 3" would be enough, but this is pure conjecture on my part.  

That is a great idea, Dave.  Thanks!  Do you think the pipe and heat tape would need to be wrapped in any insulating material in order to get to temperature?

As i see it, the tape is going to that temp at the rate of the current applied allows it and that insulation would save a lot of juice and provide a safety factor.  I like the idea of lower amperage tape and a timer (minimum costs).  I have an outer shell of 6" pipe inside which I'd suspend the heated pipe/charcoal assembly. 

Set it up, run it X hours.  Let it cool, check.  Make adjustments as necessary.  This might be my approach if i buy some heat tape.  One can build any sort of configuration of heat-treatment oven with such tape and a thermocouple and controller.

I picked up some more 12L14 yesterday, but "play" has to wait a while as I'm gone fishing for a few days.

[davec2]

Jim,

You don't need the insulation, but the temperature will come up faster and stay more consistent if you use it. In an aerospace application for something similar, I use a tube (in my case copper) wrapped in the heat tape and then wrapped with this insulation:

http://www.mcmaster.com/#high-temperature-insulation/=tzqep7

Between using copper (great thermal conductivity) and the insulation, the internal temperature in the tube is very stable.  The rig also has three thermocouples (inside the copper tube - one on each end and one in the middle) and a controller that will keep the temperature within two or three degrees of where I set it.  I have not used this set up for charcoal bluing or any gunsmithing work, but it is just a rig to keep the temperature inside a pipe at a known and controllable temperature, so I'm sure it would work in this application.

Actually, while taking engraving lessons from Jerry Huddleston a few years ago, he showed me some magnificent heat blued stuff and we discussed the precise temperature required to get a beautiful sky blue color on steel.  I thought that this rig would be perfect to do that type of blueing as well, but I have not tried it yet.  When I get a chance, I will try it and also bleed oxygen through the pipe so that the barrel is surrounded by pure O2 as the heat is applied.

[davec2]

Wade,

VOODOO BLUE !!   I love that !!!!!

[Curtis]

Dave, thanks for taking the time to post all the information, I had no idea one could get such controllable temperatures from such a rig.  You really have my curiosity peaked about the whole concept.  I may have some specific questions for you after I do some detailed study of the links provided.

For high end applications I could see this being invaluable.

Curtis

[davec2]

Curtis,

If I was even going to do just one barrel, I would invest the time and money to set up this type of controllable arrangement.  When you consider the time and trouble of doing this in a fire pit ...and the chance that the end result will not turn out well ...and that you will have to do it all over again, or worse yet, ruin a barrel completely.....well, let's just say I wouldn't do it that way.  Sometimes, you just have to invest in the right equipment to do a good job.  I like clever, old timey tricks as well as the next guy, but I wouldn't try to fell an oak tree with a pocket knife.  It's that old "right tool for the right job" kind of thing.  Even to do a credible rust blue, I need a damp box and a trough to boil the barrel.

[sqrldog]

Another way to get it done is to find a person that has the experienc to do it and do it right. Send the barrel to them and for a reasonable fee get it done right without l the expense and trouble of making your set up for one or two barrels.  Just a thought. Tim

[RAT]

Regarding using a heat treating furnace to carefully control temperature... how many people do we think have a furnace in their home shop big enough to heat a 44" barrel? Brownells doesn't even sell bluing tanks that big.

Regarding the heat tape method above... has anyone actually used this method? That looks like a perfect candidate for a tutorial post. Many of us would be interested in seeing this explained in full with pictures of the process and results.

[smart dog]

Hi Dave,
The heat tape is a great idea.  I should be able to plug the tape into my oven controller instead of the oven and then run the thermocoupler into the pipe.  Would you insert it into the bore of the barrel?

dave

[SuperCracker]

I love the smell of a wood fire as much as the next guy, but if you want consistent results with our a lot of trouble and expense, put the barrel in a black iron pipe with clean charcoal, as Jerry explains, and then use one of these wrapped around the pipe to get and keep a constant temperature for as long as it takes to get the blue you want.....

http://www.mcmaster.com/#heat-cable/=tzintq

With a single thermocouple and a temp controller you can find on e-bay for $40, you can precisely control the temperature up to the limit of the tape (~1400 degrees F).  The more precisely you can control any process, the more consistent the results.  Personally, I don't like risking a lot of hard work and parts to a process that requires the waving of chicken bones in a brown paper sack over my head on a moonless night.

I'm soooo building that set up. That's an awesome idea. Consistent, controllable and not crazy expensive..........in the grand scheme of how much gets spent on stuff like this.

[davec2]

David,

Yes, I would put the thermocouple inside one end of the pipe either next to the barrel or down into the bore.  I use these tapes and some of these types of heaters to make up any kind of an odd ball furnace I need up to 1200 degrees or so.  Higher heat takes more effort, but you can do a lot up to 1200.

http://www.mcmaster.com/#strip-heaters/=tzxv1c

http://www.mcmaster.com/#strip-heaters/=tzxvbk

DC

[jerrywh]

 I make my own furnaces so I have a 48" barrel furnace but For charcoal bluing I like Dave's idea because the temp does not have to be extremely even for charcoal bluing. For fire bluing I would be worried if I could keep the temp even enough from one end to the other.  I can control the temp in my furnace about every 8" and at the same time I can watch the colors change because the furnace has a ceramic glass top through which I put 6 digital  pyrometers one every 8".
  Jacob dicker never had one of these but he always wished he did. 
 I have one question for Dave.  Do you think the tape will heat evenly or will it be hotter on the ends or what?
 I know the copper pipe will help distribute the heat more evenly but just how good is it.  Maybe a thicker copper pipe would be better than a thin one? Also the copper pipe will defuse the light in the tube. That is good. I put a aluminum box inside of my furnace to help defuse the heat and the light. I am told by another engineer friend that the light from the heat also has an effect on the color of the barrel in heat bluing.

[jerrywh]

 I suggest using no bigger pipe than 3".   2" would be better. You can put a center spike in one end to hold the barrel in the center of the pipe. Then fill the pipe and barrel full of charcoal. The charcoal will keep the barrel on center. The charcoal will not burn up in the process no more than about 5%. Smaller pipe heats faster and the heat strip will cost a lot less. You can even save the charcoal with this setup.

[davec2]

Jerry,

The tape heaters are fairly uniform in the temperature they generate along their length. Yes, A thicker copper pipe is a little better than a thin one but I use commercially available copper pipe and wrap the heat tape winds nearly side by side.  Between the conductivity of the copper, the close wraps, and the insulation around the outside, the heating is very uniform inside the pipe.

[bob in the woods]

Too bad this requires electricity      Guess I'm stuck with the pit 

[Captchee]

 soooo ,
dig the pit and put the barrel in a casing as Jerry suggests.
All the furnace is doing is helping to control and provide a more constant heat