Reapplying bluing to steel

[rigatoni]

Couldn't find a solid answer on this elsewhere

Reapplying bluing that's worn off over time to steel... Can you just go over the top of the existing blue for a consistent finish? Does the blu penetrate where already blued?

Would it be even?

Or do you need to strip it back and start the whole thing from scratch to get an even finish?

[Jack V]

There is many types of bluing which one do you intend to use? Basic answer is adding onto existing bluing with say a cold blue will seldom be even in colour all over .
It's really a patch up system . Sometimes you can be lucky and it matches in ok and other times not so good. This is because there is many bluing processes and they all come out slightly different in colour and texture and oil and grime on the metal also changes things . To get the best outcome you do need to strip all the old blue off , polish up the metal all over , degrease the surface properly and then re-blue . The most common process used by smiths is hot caustic bluing . The polished and degreased metalwork is suspended in a vat of hot caustic salts for a short time and it sends the metal blue. Then it's washed and should be boiled in plain water to remove salts and then dipped in oil . Keeping the salts out of the bore is also a good idea but most don't bother .
Cold bluing can be much better if the metalwork is stripped back and polished up and degreased , this video gives an idea https://www.youtube.com/watch?v=X-CDOJF-TmY However to strip and polish ( buff) metalwork properly you really need to be able to remove the barrel . However it's not impossible with the barrel and action still attached just more difficult . Then you have London rust bluing which is basically once the polishing and degreasing is done you rub a rusting agent all over the metal and let it sit for 24 hours . This causes fine rust to start then you boil the metalwork in water to convert the rust to a stable oxide and then let it dry. Then polish off the black oxide with fine steel wool and do it all over again and again until a deep blue appears.
There is also several chemical formulas that can be used in a hot blueing tank other than Caustic .

[Baldrick314]

Cold or hot blue?

If you're doing a rub on cold blue you can go over the top of the existing blue and it will give a reasonably even finish but for the best finish obviously removing all the old blue would be ideal.

For removing the old blue Birchwood Casey Blue & Rust Remover works a treat. Basically effortless and really cheap.

I don't have experience with hot bluing but since you'll most likely be taking it to a smith to get done they'll be able to advise you

[rigatoni]

I haven't bought the blue yet folks so can't tell you a brand.

Cold blue is the plan? The vids I've seen just have it submerged in the blue as is for a while then removed, even a technical luddite like me can manage that I think

[Baldrick314]

I've been using Birchwood Casey Super Blue and it's given me good results, I've always removed the original blue though. I dunno about the vids you've been watching but this requires you to rub on the solution, let it do it's thing for a minute then rinse off and buff with fine steel wool. Sounds a bit more involved but does give a nice finish after about half a dozen coats.

Also heard good things about G96 blue but never used it.

Good luck with the project

[Westy]

Fan of the G96 here!!!!

[Jack V]

It's the quality of the preparation , polishing and degreasing that makes for a better job . The cold blues are all similar .

[rigatoni]

I dunno about the vids you've been watching but this requires you to rub on the solution, let it do it's thing for a minute then rinse off and buff with fine steel wool. Sounds a bit more involved but does give a nice finish after about half a dozen coats.

I've seen a few including wipe on blue methods.

The thing with the submersion ones is it seemed pretty fool proof. Obviously just dunking the think you get 100% coverage and wouldn't have to worry about more or less being on a wipe or doing it unevenly or whatever else.

I've seen dodgy blue jobs and have attributed to that, but confess that's an assumption.

With the rub on solutions is there a technique or finesse to getting things even or do you just keep rubbing until it's absorbed as much as it can and the finish will be right anyway?

[Baldrick314]

With the rub on solutions is there a technique or finesse to getting things even or do you just keep rubbing until it's absorbed as much as it can and the finish will be right anyway?

In my experience (I've done a couple rifles so not an expert) if you take care to coat the rifle evenly not concentrate on one spot you should get a good result. More important than a trick for applying the blue is good prep work though

[Tiiger]

More important than a trick for applying the blue is good prep work though

I agree. The botched jobs I've seen were all because people just opened the bottle and started slopping it on the dirty surface.

[Sakoh]

I did a knife following old Larry Potterfield's how to videos and it came up perfect.

How to Polish a Rifle Barrel to Prepare It for Bluing

How to Blue a Rifle Barrel Using Cold Blue

Video is for a barrel but you can adapt obviously.