touching up a blade with gun blue pen

A. G. Maisey · 2nd March 2022, 10:03 PM

Purely metallurgical?

OK.

I own & use a number of firearms, and have owned rifles for seventy odd years and during that course of time I have needed to touch up firearm bluing more times than I can remember.

In my experience cold blue, I normally use Birchwood Casey, will only act on ferric material, it will not darken nickel plating, thus I do not believe it will darken pure nickel on a keris blade.

However, an artist friend tells me that nitric acid @ 50% dilution will darken nickel, you need to get the nickel a bit warm, +/-50C, soak the nickel for up to 30 seconds. She is an artist, and she does SOAK the material in the dilute nitric acid, not paint it on.

Frankly I would not touch nitric acid with a 40 foot pole, it is very nasty stuff, and my belief is that it would be impossible to isolate the effect of the acid so that it only touched the nickel in the blade leaving the ferric material untouched. I think the fumes alone would be sufficient to adversely affect the rest of the blade finish.

To be clear:- I am not recommending the use of nitric acid for anything, least of all to attempt to alter the appearance of this blade under discussion.

2nd March 2022, 10:03 PM	#7
A. G. Maisey Member Join Date: May 2006 Posts: 7,048	Purely metallurgical? OK. I own & use a number of firearms, and have owned rifles for seventy odd years and during that course of time I have needed to touch up firearm bluing more times than I can remember. In my experience cold blue, I normally use Birchwood Casey, will only act on ferric material, it will not darken nickel plating, thus I do not believe it will darken pure nickel on a keris blade. However, an artist friend tells me that nitric acid @ 50% dilution will darken nickel, you need to get the nickel a bit warm, +/-50C, soak the nickel for up to 30 seconds. She is an artist, and she does SOAK the material in the dilute nitric acid, not paint it on. Frankly I would not touch nitric acid with a 40 foot pole, it is very nasty stuff, and my belief is that it would be impossible to isolate the effect of the acid so that it only touched the nickel in the blade leaving the ferric material untouched. I think the fumes alone would be sufficient to adversely affect the rest of the blade finish. To be clear:- I am not recommending the use of nitric acid for anything, least of all to attempt to alter the appearance of this blade under discussion.