Really though, blackening is a period, durable, rust resistant surface finish, plus it's a lot easier and faster than polishing.
There are a whole lot of different ways to make your armour black, This is the one that I use.
Step 1: What You'll Need
You'll also need oil in a spray bottle. These days I use linseed oil, but in the past I've used WD40 and Olive oil, both work well.
Lastly, a rag or some sort, and maybe some gloves.
I shouldnt have to say it, but a fireproof surface you don't worry about making a mess on is a good idea. I have a sheet of aluminum on a couple bricks here.
Step 2: Blackening.
Start off by firing up your torch and heating the surface of your armour. Pretty quick you'll see a line where the moisture in the pores of the metal is evaporating. play the torch across the entire surface until you have removed all that moisture. It should only take a minute or two. I have no science to back this up, but I suspect that by removing that moisture it allows the oil to soak into the pores, giving the finished blackening that much more of a hold on the steel. Also it preheats the metal so the oil will spread into a film a bit easier.
Got that done? OK, put the torch down to the side, grab your spray bottle of oil and unload a bunch of oil onto the metal. Once you've done that grab the rag and wipe it into a smooth coat.
We're halfway done now.
Next grab the torch again, move around to the back side of the armour and start heating. The biggest reason I do this from the back is that it makes it easier to see how dark the oil is getting. Pretty quick it'll start to go golden brown, then a deeper plum brown, next it gets a bit of a reddish hue to it and from there it will darken to a glossy black with some reddish brown undertones.
If you over heat it the oil can start to flake off, if that happens I finish the rest of the piece then come back and spot blacken that spot again.
I've always gone to black, but since linseed oil is a drying oil I suspect that you could stop at any point in the process and let it dry in that colour, I could also be wrong though, anyone here know? With olive oil and WD40 I've found that you need to go all the way to black or it just stays a tacky mess.
I usually do 2 or 3 coats of oil. I lacked a third hand to take pictures of this, but for the second coat I bring the torch back around to the front of the armour and I spray oil onto the armour in the middle of the flame and work my way over the armour till it's completely
covered again. I find that what the flame doesnt burn it forces into a film before it can drip and run. Then I bring the torch back around back and heat it like before.
I let the armour cool after the second coat, then look to see if there is anywhere that needs touching up, if there is I oil and blacken just those spots for the third coat.
Step 3: It's Done
Here's a couple of other pieces I've blackened. The spaulders are with olive oil and the trench plate was done with WD40