Cold Blue Touch up

[solman]

Hi All,
I picked up a Marlin 39a made in the 40's as a shooter gun. It shot fine at the range with no failures of any kind. I was thinking of doing some touch up work to the blueing on the receiver but not sure how to proceed. This gun is older than me and I don't mind that it shows its age. However I would like to redo some of the glaring finish faults that this gun does have. The finish on one side looks to be uneven as if someone did a touch up but it didn't blend well at all. Can I just go over the existing finish with some cold blue?
Should I strip that side of the receiver and do a cold blue refinish or maybe just leave it be. I bought some Brownells Oxpho blue and I also have the Birchwood cold blue at home but I do not have a lot of experience using these products. Any advice would be greatly appreciated.
Thanks I will try to post pictures later today.

 

[carbine85]

If you are sure you want to refinish the old piece I will recommend the Oxpho blue. So far it's the best cold blue that I have found. The metal prep is the most important part. You might want to try rust bluing. It's more work but it's better than the cold blue. Either way you go you probably should break down the rifle so that you can work on each piece.
IMHO, some of these old darlings look better if left alone. I don't see them as project guns unless there is some family heritage to preserve.

 

[BBBBill]

Cold blue is not really intended for a complete refinish. Any brand of cold blue is a poor substitute for a proper hot blue or rust blue. It is just not very durable at all and trying to match a previous blue is an exercise in frustration. That said, Oxpho is probably the best of them.

 

[LAGS]

@ Solman
The Marlin has a lot of Flat surfaces and it is very hard to cold blue and make it look right.
I would say, for at home, try the slow rust bluing method.
It is a lot of work, but you will be very satisfied with your efforts.

Cold Bluing is fine for small parts, and maybe the touch up of a scratch just to get temporary rust protection.
But to prepare the metal correctly, and get the finish even is very hard on large parts.
Plus,
Cold bluing if let to sit on Existing bluing will eat the old finish right off, making it hard to Blend your touch up.
And blending your touch up at sharp corners is even harder since the corners polish off so easily and will always look thin or shiney.