Blueing

[Peter KroghParticipant @peterkrogh76576]

Rust blueing is the process of producing rust then brushing it off (carding). The first few cycles won't leave much finish but about 6 cycles starts to produce a blue. A dozen or more makes the deep, hard, blue seen on old Mausers and such. Takes about a month minimum to produce that fine finish.

Rusting solutions vary and can be found in many old books on the subject.

Pete

[KenLParticipant @kenl]

The process of blueing/browning as practised for hundreds of years by gunsmiths is very simple, I've done it many times on shotgun barrels in the distant past. It can produce a fabuous finish but takes time and patience.

Browning and blueing is exactly the same process except for the boiling of the final product to change the colour. The item to be treated is first degreased then covered in a rust promoting liquid. This liquid can vary considerably and there are many old recipes that claim to be the best, most of them containing ingredients that would be very hard to obtain these days. the most common ingredient used would usually be copper sulphate along with various acids/nitrates/phosphates (and usually urine). In truth the same result can be obtained with plain old water – but it takes much longer. After coating with the rust promoter the item is placed aside in a damp environment for a few days to develop a coating of rust, most of which is then removed with wire wool. The process is then repeated numerous times until a deep and even coating of rust remains. If a brown finish is required it would then be washed, waxed and polished. If a blue or black finish is required then the item would be immersed in boiling water until the rust turns the required shade of blue, followed by waxing and polishing.

This old process can produce a superb and durable finish if properly done – but it can take weeks or months to develop a deep satin blue sheen.

[Stuart BridgerParticipant @stuartbridger82290]

This is a practical example of two different techniques, not recent I add. There is some wear, but it does illustrate the durability, albeit with the limitations of the photo reproduction

The one of the left  I made at school, I think in 1978 and was blued by heating and dipping in in old engine oil.

On the right was an apprentice piece, made in 1980 and phosphated using a commercial process.

Edited By Stuart Bridger on 30/03/2023 08:29:03

Edited By Stuart Bridger on 30/03/2023 08:30:57

[petro1headParticipant @petro1head]

Got my blueing and had a first attemp but i suspect the part was not properly degreased. Just wondering what people use to degrease? Could i use brake cleaner?

[Sonic EscapeParticipant @sonicescape38234]

What method did you used in the end? How does it look like? Acetone is a nice non toxic degreaser and is widely available.

[Mick B1Participant @mickb1]

Posted by petro1head on 31/03/2023 11:09:31:

Got my blueing and had a first attemp but i suspect the part was not properly degreased. Just wondering what people use to degrease? Could i use brake cleaner?

I used a wipe with meths followed by a hot wash in washing-up solution, then apply the bluing with a soft paintbrush while the metal's still hot. Wash again (in rubber gloves), dry, and oil up when happy.

Edited By Mick B1 on 31/03/2023 12:19:48

[SillyOldDufferModerator @sillyoldduffer]

Posted by petro1head on 31/03/2023 11:09:31:

Got my blueing and had a first attemp but i suspect the part was not properly degreased. Just wondering what people use to degrease? Could i use brake cleaner?

Yes, or acetone, or soapy water, perhaps in combination. Like glue, the secret of success is absolute cleanliness.

Things likely to spoil bluing:

• Steels that resist corrosion in any way, not just Stainless
• Steels that have already been treated – painted, phosphated, galvanised. These processes go deeper into the metal than might be expected, and have to be removed.
• Metal were the surface has already been damaged by corrosion, welding, folding, stamping, heat-treatment etc.
• Oil and grease are also hard to remove completely because they penetrate into microscopic cracks and crevices. At the molecular level even highly polished surfaces are full of ravines and caves that catch and hold dirt.
• Abrasive cleaning methods such as sandpaper or sand-blasting that tend to leave abrasive material stuck to the metal (in non-obvious microscopic quantities)
• Handling on a grubby bench with anything other than clean rubber gloves and clean grease-free paper or cloths.

So, depending on how dirty the item might be, and how important it is to guarantee a good finish:

1. Choose a steel that blues nicely
2. Sand-blast or surface grind to remove deep problems, then
3. Wire brush clean, followed by
4. Strong degreasing, maybe boiling in caustic soda solution, followed by
5. Water rinse to remove degreaser and muck, then
6. Acid wash & short soak (to remove any remaining degreaser, and neutralise alkalis, also flux and oxides if present), followed by
7. Hot water and detergent wash (to remove remaining grease), followed by
8. Deionised water rinse (to remove detergent and tap water contamination), then
9. Alcohol rinse (to remove water), then
10. Spray liberally with Brake Cleaner or similar, to deal with residual grease. As soon as dry proceed quickly to the bluing process
11. Apply a reliable bluing process, and practice it first

Most of the above is optional. I don't attempt pretty bluing, or care if results are uneven and blotchy. I wipe off the worst with clean kitchen towel, check to see how grubby it was repeating as necessary, and if OK I wipe again with the towel soaked in brake or carb cleaner, then a quick spray to finish off. (Rubbing tends to leave fibres struck to the metal.)

Rough stuff mostly in my workshop. I'm more likely to splash phosphate on rust than do a proper job. However, I'd throw the book at it if I was starting with dirty metal and especially if it was important to guarantee the finish.

Most of what I make isn't for show or intended to last. Others make lovely clocks that become heirlooms and models that win Gold Medals in competitions! Their secret is perfectionist attention to detail, and not the corner cutting for quick results I prefer.

Dave

[petro1headParticipant @petro1head]

Posted by Sonic Escape on 31/03/2023 11:24:44:

What method did you used in the end? How does it look like? Acetone is a nice non toxic degreaser and is widely available.

I bought the Nickerson. Results was very patch but i suspect i did not clean and degrease properly

[Rod RenshawParticipant @rodrenshaw28584]

Stuart's photo illustrates well that most bluing methods (with the exception of the gentle heating to tempering colour method explained by Martin in his post above) result in a black or nearly black colour. I wonder why it got to be called bluing?

Rod

[Martyn Edwards 2Participant @martynedwards2]

Now retired but back in the day many moons ago when teaching metalwork we had a tank of 'Whale Oil' that was used for blueing.

[bernard towersParticipant @bernardtowers37738]

Rod, I think you will find that blacking and blueing are two different processes. Blueing in the home workshop is a temperature sensitive process and blacking is a chemical one. On choices of material for blacking stay away from alloys that contain any chromium, don’t ask me how I know!

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