Cold bluing turns rusty brown

[8tharmy]

Hi all,

Lately I've tried to cold blue my real sword and the result turned out to be well, but when I tried to blue the upper reciever it went disastrous, I sanded the old blue off fully washed it and applied new gel on with swabs, it looked good at the beginning hut after drying it almost immediately turned into a rusty brownish color, anyone know why is it like that?

[Spencerman]

Ok, I will have a stab at this but I am a little rusty myself when it comes to blueing, but I used to do it all the time many years ago.

 

The first thing that I will ask is are you using the correct blueing solution for the correct metal? If it is steel, then no problem there, as blueing is a rust process. If it is aluminium, then normal blueing solution is not any good, as aluminium doesnt rust, so it cannot complete the process. For that you would need to use something like Aluminium black, which does basically the same thing, but in my opinion doesnt look as nice as blue.

 

The second question that I would ask is have you prepared the surface correctly? It may sound silly, but I would sand and smooth for hours to make sure that the surface was absolubtly perfect before blueing, as the end result would end up vastly better due to the prep work. Needless to say you have to make sure that you have no trace of oil at all before you blue, otherwise it will not take. I also preferred to use the blue gel myself, it is much easier to apply, unless you are doing a load of guns and parts at once, in which case you would be better off dunking them. I also used to use a small paint brush to apply it, the key is to try and apply it as evenly as possible.

 

Now, here is the part that I cannot remember, but I am sure that your blue will tell you on the pacjaging. For a warm blue finish, you leave the blue on for about 30 seconds, before you rinse it off. For a cold blue finish you leave it for longer. You repeat the process until the desired effect is reached. I wont even bother mentioning anything about case hardening as that really is of no use to airsoft, as I doubt the parts would be upto the process. Similar to paint, you are better to use four or five coats than to slap it on really thick, as I mentioned earlier, blueing is a rust process, so it makes no difference how thick you apply the blue, it is only the process that has the the effect, not the amount, so the most important thing is to apply it evenly to give an even finish.

 

Once you have done that, and rinsed off all the blue solution you will be left with a dull black looking finish, which is the stage that it sounds like you have reached from what I have read. This will be pretty much the same for warm blue or cold blue. The last process is where the magic happens, and you find out whether you have to start all over again or if it is ok! You have to oil it. Apply plenty of oil, be very liberal with it, the more the merrier, and let it soak. That should then give you your finished result. Belive me, the extra work in the prep stage is worth it, as the slightest marks or imperfections will show through once you blue it. If it is not as you want it, then you have to clean off all of the oil and start again giving it more coats if it is not blue enough, or strip it completely if it looks ######.

 

Oh, and wear gloves and suitable breathing apperatus, blue solution is an extreme irritant if you inhale it or get it on your skin, one of the reasons that I always preffered the gel.

 

I hope that this helps, and I am sure that if I have got any of that wrong someone will soon correct me, but this is all based on my own previous experience, and I have always had results I am happy with.

[8tharmy]

Thanks for the professional reply! The first time I blued my gun it turned out so well, nice deep blued finish and I didn't do a proper preparation, the second time I sand and cleaned the part throughly before I applied the blue, but it turned all brownish after it's dried, almost poke browning than bluing, Im not sure where it went wrong