How to Turn Steel Black - All you need to know about Bluing

[PeterT]

From the rebuild master himself. My experience has been identical to this. Only thing I'd add is
- I find no benefit to the cold water wash off, I go straight to oil
- count on fade & coat thinning over time, accelerated by wear
- some steels are just problematic, especially rolled products or with scale remnants

 

[Dabbler]

@PeterT He misses out on showing the heat bluing (no quench) that clickspring uses, another beautiful and practical form of bluing:

[check out 1:39 for a beautiful transition]

 

[6.5 Fan]

Those methods shown of bluing are very basic. There are lots of other methods, some requiring heated tanks and caustic liquids also cold blue methods that don't need a lot of equipment just a good sweat box and time, ie rust bluing. A lot of books have been written about bluing, hot and cold.

 

[PeterT]

Sorry, maybe 'all you need to know' is a bit strongly worded. But that was his title choice, not mine. I just pasted it in and FWIW mentioning this has +/- been my experience as well on these 2 particular methods. Good luck!

 

[historicalarms]

I have never done any "hot bluing" because I never planned on doing enough of it to make the equipment/chemical purchase worthwhile but i have done a considerable amount of 'cold bluing.
Cold bluing is not a "one brand fits all" situation. Some metals take a very good bluing from one brand ( there are at least 1/2 dozen different brands of chemical mix's that i know of, and I keep a bottle of each around all the time) but the next chunk will be very "splotchy" with the same chemical....you just never know what your going to end up with until you try a test spot.
I have a full length Octagon barrel that I cut from a round blank, draw filed and emoury clothed the mill marks out of it and cold blued it....I would defy anybody with gun barrel finish experience to tell that that barrel wasn't hot blued. I used the barrel stub cut-off as a test piece & picked the brand that offered the best coating on the first application. I then applied 3 consecutive coats to the actual barrel , total time was about an hour and cost was maybe $5 worth of chemical out of a $10 small bottle ( hot bluing would have been a minimum of $ 150 commercially done) .
Actually, the most important secret to getting a good bluing finish from any combination of chemical or steel is to absolutely de-grease the metal dilligently...do not cut any corner's here...use a properly labeled "de greaser" meant for bluing steel.

Another thing about bluing....if you want to know how good the metal finishing is that you are doing, just dabb a bit of cold blue on your metal....blemishes of almost microscopic size will glare at you , and as a mad woman's glare, it will be easily & plainly seen.

 

[StefanMFrey]

The video shows the use of an oil spray once the cold bluing liquid is applied, rinsed and dried off. What kind of oil are you using for this step? Thank you, Stefan

 

[PeterT]

I've tried a couple different oils & cant quite tell much difference. WD40 (which is probably as much solvent as it is oil) seems to penetrate & hold the color. He is suggesting keeping part immersed in oil for a while. I guess I've left some of my pieces oily like over night but again didn't see much difference. Soaking may not be practical for large pieces anyways. My commercial tools look blacker & coating lasts longer so I'm guessing they use a more industrial and/or extended heated application. That's not something I really want to get into so its one of these 2 methods & live with the results. Mostly I use the cold blue stuff.

 

[Dabbler]

When I do a quench bluing, I put the pot on the burner and keep it and the oil hot for about 15 minutes. From my limited experience it seems to give the oil time to bond/fill in the cracks/ bake in -- or something.

 

[YYCHM]

When I was building miniature cannons I used Map Gas to silver solder the trunnions on.

I noticed that the heating process left a nice dark color to the steel that didn't rub off, so I torched the whole thing. A little oil and voila instant blackening what ever it is. Still going strong and hasn't rusted.

 

[historicalarms]

Craig, torch bluing is a real thing that has been use a lot in the custom gun world, mostly for screw heads but even for complete muzzle loader creations ( the vendor will be quite proud of his work it seems as cost increases considerably to a finished item).
Of course, hot bluing remains the industry high water mark and some companies have perfected the operation to be their selling point.... Colt's for example have perfected a metal finish & blue-black bluing to be legendary quality that all others strive to copy & obtain but never seem to be able to do.

RE: oil after bluing, I have never oiled a part after cold bluing and don't notice any degradation after some years of exposure.

Another trick i discovered long ago when doing a very small touchup to an already blued piece of steel. it is very hard to "match" old hot bluing to new cold bluing on a very small spot (say you touched a spot with a file or screw driver that left a shiny mark) so, in this instance I will use a permanent Jiffy Marker to place a dab exactly where I want it and usually the spot will disappear to the naked eye unless your looking for it....and it lasts forever....until you oil over that spot LOL.

 

[YYCHM]

Craig, torch bluing is a real thing that has been use a lot in the custom gun world, mostly for screw heads but even for complete muzzle loader creations ( the vendor will be quite proud of his work it seems as cost increases considerably to a finished item).
Of course, hot bluing remains the industry high water mark and some companies have perfected the operation to be their selling point.... Colt's for example have perfected a metal finish & blue-black bluing to be legendary quality that all others strive to copy & obtain but never seem to be able to do.

RE: oil after bluing, I have never oiled a part after cold bluing and don't notice any degradation after some years of exposure.

Another trick i discovered long ago when doing a very small touchup to an already blued piece of steel. it is very hard to "match" old hot bluing to new cold bluing on a very small spot (say you touched a spot with a file or screw driver that left a shiny mark) so, in this instance I will use a permanent Jiffy Marker to place a dab exactly where I want it and usually the spot will disappear to the naked eye unless your looking for it....and it lasts forever....until you oil over that spot LOL.

For small dark touch ups I've had pretty good luck with Birchwood Casey Aluminum Black.

 

[Dabbler]

I always wanted to learn Parkerizing, but never found an appropriate project to apply it to. Still not a perfect finish, but a little better than bluing.

I'm not impressed with Cerekote - tried it several times, using all the recommendations, spent big gucks. I even got the manufacturer to CereKote some of my coupons, for a price. Every one easily scratched off, including the factory applied ones on 303 SS, 1018, and 4140.

 

[YYCHM]

I always wanted to learn Parkerizing, but never found an appropriate project to apply it to. Still not a perfect finish, but a little better than bluing.

I'm not impressed with Cerekote - tried it several times, using all the recommendations, spent big gucks. I even got the manufacturer to CereKote some of my coupons, for a price. Every one easily scratched off, including the factory applied ones on 303 SS, 1018, and 4140.

I re-parkerized a Webley revolver, turned out great!

http://www.pjsproducts.com/radocy.htm

No experience with Cerekote.

 

[DavidR8]

I always wanted to learn Parkerizing, but never found an appropriate project to apply it to. Still not a perfect finish, but a little better than bluing.

I'm not impressed with Cerekote - tried it several times, using all the recommendations, spent big gucks. I even got the manufacturer to CereKote some of my coupons, for a price. Every one easily scratched off, including the factory applied ones on 303 SS, 1018, and 4140.

Hmmm that's good to know as I was thinking of Cerakoting some moto parts.

 

[PeterT]

YYCHM, re your link werre you talking about the Zinc parkerizing or the Express Rust Blue? I'm wondering about Rust Blue , what they call the hot water treatment? Is the water bath purely for an evenly distributed & target temperature & then you wipe on the blue? Or do they mean the chemical is added to the water & part goes in the bath? $65 for 4 oz (gasp) how far will that go?

This EXPRESS rust bluing method is the HOT WATER water method of bluing. You immerse the part in boiling water to bring the metal up to temperature and you must maintain the temperature throughout the process.

 

[YYCHM]

YYCHM, re your link were you talking about the Zinc parkerizing or the Express Rust Blue?

For the most part the Parkerizing solution, but I did get some very good cold bluing solution from them called Van's instant gun blue that they don't appear to carry anymore. Was good stuff.