Heat Blue - help wanted

[Acer Saccharum]

I'm getting ready to blue my jaeger barrel. It has gold inlay work.

I know there are different ways to do this.
a)Jerry uses a special kiln, with several zones.
b)I approached my commercial heat treater, and they have a nine zone furnace where they can really control the heat to plus/minus five degrees.
c)heating the barrel in a bed of hot sand over the forge.

I have to say that 'c' appeals to me the most, since it's close to what the original makers may have used. if anyone has experience in this area, I would love to hear about it.

Some thoughts:
1)New sharp sand. Need I be concerned about it  scratching the barrel? is there a better medium than sand? eg: bb's or steel shot?
2)grease and oil are a concern. Do I degrease the hot barrel with lime?
3)Most originals I have seen show slight varying shades of blue, from watery blue to dark blue, to brownish purple. Some variation in the color is fine by me.
4)If I don't like the results, I can polish the barrel bright again.

Any thoughts appreciated.

Acer

[T*O*F]

Acer, you forgot d. and e.

d.  Pure wood charcoal in a pit dug in the ground.  Barrel placed in the coals and the top of the pit stopped down to regulate the temperature.  I think this was the most traditional method.  I remember EK writing about this many years ago.

e.  Nitre blue.  Potassium nitrate is placed in a bluing trough and heated until it melts.  Since the melting point remains constant, there is no need to regulate the temperature and the color will be the same each time.  This method is commonly used for small parts which are dipped and removed.  However, given a long soak time the oxide coating "should" be thicker and yield increased permanence.
Brownells sells it in 25lb quantity.  I don't know if regular fertilizer would work or not.

[Acer Saccharum]

Dave, I don't want the dark Charcoal blue, as you probably know, but I write just to be certain. I want the temper colours, which will be approx. 500 to 600 deg F. This blue is quite fragile, but two hundred year old examples still have traces of their blue.

Would I put sheet metal over the fire to slow it down? It seems reasonable that I could control the fire and get decent results. Not a lot of money invested in a furnace, just a ditch, charcoal, and some sheet metal scraps. I would certainly want to test on a polished bar or tube.

[Dphariss]

You want the heat blue. This can be done with potassium nitrate as well.
It is probably easier to just have it done in a furnace.
But it must be perfectly degreased.
I would use acetone. Twice at least.
But if they run the color just little too high the color fades. The advantage to nitrate is that you can watch the color develop since the pure P.N. should be clear when melted. But it takes a long enough tank, a lot of heat and the nitrate evaporates, turns into oxygen, when in a liquid state. Leaving parts once color is reached requires a temperature control or very careful watching to prevent overheating.
Also that once is has cooled and solidified when remelted it needs to be heated along the sides as well as the bottom for subsequent uses or there is a risk of bubbles of oxygen forming under the hard crust and then "burping" with greater or lesser levels of pressure.

I have never done a barrel just small parts. Springs, lock plates etc.
Its fairly durable.

Dan

[Jim Filipski]

Tom what ever you decide on "photo record" the progress! ( Just so us others know what not to do when it's our turn) I'm still considering that red hot mandrill ( Piston)  Can't see how it would affect the bore negatively. That jaeger thin water blue only need to appear on the 5 visibles
Jim

[lew wetzel]

tom,if it turns out ugly and you dont like it,you can just send the barrel to me and i will take c are of it for you while you start over with a new barrel.i think i would be helping you out tremendously.........lol

[Jim Chambers]

When Bivins, Harn, Ehinger, Wayne, and I made the rifles for Last of the Mohegan the barrels were niter blued.  That was the most beautiful blue color I've ever seen on a gun.  I'd highly recommend that method.  Too bad the movie producer didn't like that color.  It broke my heart to have to polish them back bright.

[rich pierce]

If I know Acer, he wants to be able to say he fire blued it.

[Acer Saccharum]

Right again, Rich

[flintriflesmith]

Acer,

I think you will find this much easier than you are expecting it to be.

If you are not limited to period methods but just want period looking results you can simply hang the barrel by a thin wire through the front loop and, starting at the breech, "chase" the blue up the barrel with a map gas torch or even a propane with a flame spreader. I would recommend taking the rear sight off because the thin sight blade will overheat but if you take your time and pay close attention it is fairly to get an acceptable draw blue this way.

I've done two longrifle barrels and one pistol barrel this way.

Get a high polish first and as others have said completely degrease it including the breech threads. If I remember correctly I backed the plug out a few turns on one barrel and you could do the plug separately.

If you over heat it and go past the blue you can just polish it and have another try.

Gary

[bob in the woods]

Gary, ...that is exactly the way I've done it!  3 rifle barrels and 2 fowlers. It is easy if you are carefull, and after a bit, you actually get a "feel" for it, chasing that beautiful colour up the barrel. A rifle that I built in 2003 and use regularly, has this barrel treatment, and it still looks great. I wax the barrel every once and a while.

[Acer Saccharum]

Thanks, all, for your input. I DO want to be able to say I 'fire blued' the barrel, as Rich said in very small print. I want to use fire. So I will get out the charcoal, and the camera, and record as I go. Practicing on scrap first, naturally.

Gary, I have experienced grease seeping out of the breech threads while rust bluing, so I imagine that grease in the threads will seep onto the surface if I don't remove it.

Similarly,  before I pound the gold into the engraving, I must degrease those areas very well. Otherwise, I'll have blotches of a different color blue around the inlay work.

Thanks again, y'all.

[T*O*F]

I DO want to be able to say I 'fire blued' the barrel,

OK dude, here's the downside.  If you use the pit method, you have no control over the color.  From the time you put the barrel in to the time the fire goes out and it has cooled in the ashes, you really can't see what is happening, although you can remove the lid and look.  But then you have to re-regulate the temp.  Temp is regulated by pine splinter....see next para.

Everything has to be highly polished for best results.  For the forge or stove methods, there are alternatives.  You can use sand, finely ground charcoal, or wood ashes in a metal box on top of the forge.  The sand should be white silica sand as used in sandblasting.  You buy it in 100 lb bags.  The charcoal must be pure wood charcoal, not bound briquets.

You build your fire and uniformly heat your media, stirring it while heating.  When it will just ignite a large pine splinter, it's ready.  Bury your barrel in the media.  Have a polished piece of steel to lay on top.  When the top piece hits the color you want, remove the barrel and heavily oil it to stop the action.

The last method involves only a heavy steel plate on the forge/fire.  Lay the plate over the fire with the barrel on it.  Everything will heat up together and go thru the changes.  When the barrel hits the color you want, take it off and rub with heavy oil to stop the action.  This is probably the simplest method.

Lastly, I think the color that you are looking for is the pale blue.  I have looked at my sources because I remember the term "water blue."  However, I have not been able to find the method to achieve it.  I do recall that the color only occurs very briefly as a transitional phase at a very narrow temperature range.

Again, you want your barrel to be mirror bright.
Gud Luk

[Acer Saccharum]

I DO want to be able to say I 'fire blued' the barrel,

OK dude, here's the downside.  If you use the pit method, you have no control over the color.  From the time you put the barrel in to the time the fire goes out and it has cooled in the ashes, you really can't see what is happening, although you can remove the lid and look.  But then you have to re-regulate the temp.  Temp is regulated by pine splinter....see next para.

Nope, no charcoal pit for this dude. Sounds too strong and wild.

Everything has to be highly polished for best results.  For the forge or stove methods, there are alternatives.  You can use sand, finely ground charcoal, or wood ashes in a metal box on top of the forge.  The sand should be white silica sand as used in sandblasting.  You buy it in 100 lb bags.  The charcoal must be pure wood charcoal, not bound briquets.

Dave, This is what I think I will do. I have forge, white silica sand, real wood he-man charcoal, steel plate.

You build your fire and uniformly heat your media, stirring it while heating.  When it will just ignite a large pine splinter, it's ready.  Bury your barrel in the media.  Have a polished piece of steel to lay on top.  When the top piece hits the color you want, remove the barrel and heavily oil it to stop the action.

Sounds good, sounds good. I can do this.

The last method involves only a heavy steel plate on the forge/fire.  Lay the plate over the fire with the barrel on it.  Everything will heat up together and go thru the changes.  When the barrel hits the color you want, take it off and rub with heavy oil to stop the action.  This is probably the simplest method.
I think I would get hot spots with this method, eg. where the barrel is contacting the plate.

Lastly, I think the color that you are looking for is the pale blue.  I have looked at my sources because I remember the term "water blue."  However, I have not been able to find the method to achieve it.  I do recall that the color only occurs very briefly as a transitional phase at a very narrow temperature range.

I am actually not sure what color I am looking for yet, but the pale blueis above purple ad dark blue. Jim Filipski put the 'water blue' into my head, and he might be just picking on me again, but it's hard to know when he's serious.

Again, you want your barrel to be mirror bright.
Gud Luk

Yes, I will get this barrel polished bright as can be. As in color case hardening, the higher the polish, the better the colors show.

Again, I must thank all of you guys for your ideas and support.

[Stophel]

If you want the bright, temper blue, my vote is for the professional kiln.  They will be able to get it  perfectly colored all over (theoretically).  Besides, 250 years ago in Germany, this was not a backyard operation either.  They were professionals and used big, closely controlled kilns to do this.

It's pretty, but rubs off with your fingers.  I have one early 18th c. German gun that is completely brown now, but there is one small trace of shiny bright temper blue on the bottom of the barrel under the nosecap.  I'm sure it didn't last long.  I can imagine that a lot of gun barrels that are now finished "bright" were originally temper blued, but the blueing just rubbed off.

 

[flintriflesmith]

Chris,
I agree that in 200 years the remains of temper blue are hard to find but here's a pistol I did 32 years ago and the mounts and barrel still retain 90% of the blue.

It definitely did not rub off on the owner's fingers as he carried this pistol a lot. The scratches on the guard are from his belt buckle and the rivits in his jeans--he's a shooter not a period clothing kind of guy!

http://www.flintriflesmith.com/GunshopEraGuns/iron_mounted_pistol.htm

Gary

[jerrywh]

Fire blue is a lot more durable than most people think. It does not rub off. In fact I have polished it lightly with fine steel wool after blueing. It is the acid from stuff like mustard and citric products tha tremove it. Especially vinegar. It is about the same as cold blue for durability.

[Stophel]

Maybe it's acid from skin oil/handling that takes it off, not necessarily the rubbing...

[Acer Saccharum]

Both pictures of the same gun. 18th Cent long fowler, German. This appears to be fire blue, very highly polished steel, still retaining much of its original color, with some blue missing in places of high wear, but very much intact. I doubt this piece was ever fired, as the frizzen shows maybe one strike.

So, the blue is very stable, unless subjected to high wear or acids.

Photos courtesy of the Metropolitan Museum, NYC.



I suspect the tang is case hardened and polished bright. Barrel shows nice watery blue at the breech, getting darker toward the muzzle. There is a bunch of silver inlay just ahead of this breech section, and maybe it had been polished, wearing the blue off a bit?



This is the inlaid area. Note how clean the frizzen face is. Nice inlay covering three flats of the barrel. How the heck do you inlay a piece of silver that big without bulges or buckling? Maybe it's wire inlay, where wires are  laid side by side to fill an area. Jerry, you had told me about engraving the precious metal inlay after it's all pounded in place and polished. I note here, for the first time, that the metal inlay is engraved, lines between silver and steel to highlight and define the inlay better. You can see these lines dark upon the shiny steel on the flat closest to the lock.  This is a fine piece of work.

[Stophel]

The Sprengel book says something about rubbing oil or something on the barrel while it's hot.  I wonder if there's something to it beyond simple temper color...

[keweenaw]

The absolutely clean metal would be very subject to rusting after you removed it from the heat so the rubbing of oil on  the now colored metal while it was hot would prevent that.  The temperature of the treatment isn't high enough to burn any of the oil into the surface to influence the color.

My only concerns about doing this over a fire or on some sort of heated plate are about keeping a uniform temperature along the length of the barrel.  If part of it is too hot, you'll lose the color and if part is too cool, you'll get purples, etc.  Too long at temperature will result in a considerable darkening and loss of that nice sparkle.  Short of having a trough of nitre over a pipe burner, I rather like Gary's approach of chasing the heat up the barrel with a torch.

Tom

[Acer Saccharum]

Stoph, one source I read said to wipe the barrel with lime while heating, perhaps to degrease it. Maybe the lime does something else.

Snyder, I have heard of brazing on a forge like so: cover the fire with an iron plate with a hole in the middle. The fire comes through the hole in a concentrated flame, not unlike a torch, or, like a torch, in other words.

I imagine if I have a heated plate with sand on it, there will be a high temp spot right over the fire. I can watch the colors develop, and move the barrel as the colors come up.

While the metal is just starting to heat, did you ever notice condensation forming on the surface? I am hoping to avoid that by bringing the heat up slow. The sandbed should help, too, since the gasses from the fire will not be flowing over the barrel.

[Rick]

Jim ~ Could you/would you go into more detail on the niter blue to which you referred?  Rick

[flintriflesmith]

Stoph, one source I read said to wipe the barrel with lime while heating, perhaps to degrease it. Maybe the lime does something else. ...

I fairly certain that the wiping the barrel with lime comes from Lynton McKenzie and it was based on research from England ON CHARCOAL BLUING not temper blue. I believe Lynton said it was to help eliminate variation in color. It seems to shift the grey color more toward blue-black.*

* The guys at the Colonial Williamsburg Gun Shop started doing that shortly after George Suiter attended Lynton's engraving class. I never did it because I could find no period document or even American reference to the practice. Also the color they got didn't match the patches of period charcoal blue I had examined.

Gary

[jerrywh]

If you rub it with lime it will not fire blue well at all. It will tend to go to grey. I can't tell you why It just does.  Try it on a small piece and you will see for yourself.