[J. Kemp]

This might have been covered before, but can anyone enlighten me as to what methods were used historically to blacken and rust proof plate armour?

I am told that some was blackened via burning oil onto the metal(which is the method I use on my armour), and other people might have used paint, but I know there are more than just those..

I don't have a period in mind, as I understand that different methods would have developed with time.

Just as much, if I have my facts wrong about burnt oil being one of the ways, I would be delighted to be corrected.

Anyway, the point of this is to make my rust proofing as "authentic" as possible


Thanks for any suggestions

[Craig Johnson]

HI J

In most cases it would have been paint. In cases where it was intended from the start i.e. like a black and white armor, the area to be painted was not often even finished but left black from working. The paint is often quite rough and thick in pieces I have seen with original surface still intact.

They definitely did heat blueing to achieve a brighter blue type color. While this may help some with corrosion it was for the look. Just heat blue will not deter rust much at all.

As to using burnt oil I am not aware of any proof such was done in period. Its possible but it would not have been commercial types of oils if they did. I am not sure what kind of finish one would get from olive oil? I suppose it could work along the lines of a cast iron pan being seasoned. But use of heat would affect the hardness one may have achieved so they often did not use heat processes to finish armor that they wanted to leave hard. Such things as heat blueing, gilding and the like would remove the hardness achieved by quenching.

Best
Craig

[Mark Griffin]

Blueing is done on high end armours only and does nothing to inhibit corrosion. Nowadays its easy to take a cheaply made cruddy helmet and stick it in a gas flame and blue it, then it was a highly specialized technical art form that only the wealthy could afford. It was usually done in conjunction with other techniques such as gilding, etching etc to complement each other.

You can simply leave metalwork black from the forge, sealing the carbon in with an oil or grease of some type. Olive oil is an expensive option when there were other fats available. I have simple arms that were hot worken and then wiped down with pig tallow, still nicely black despite well over a decade of wear and tear.

Paint is another option. An oil based lamp black pigment seems to be the main type, although coloured varnishes might also have been used.

[J. Kemp]

Thanks guys!
That's considerably more than I expected to learn

Thank you!

[Pieter B.]

[Mart Shearer]

[Peter Spätling]

Blackening was done most of the time by burning oil onto the surface. That's much faster than painting the armor. The oil paint which is applied to some "black sallets" for example takes weeks to dry completely. Blackening with oil is really easy. And you can use many different oils to blacken the armor.

About the annealing, yes as you need a temperature between 280°C and 450°C you do anneal the armor. One important factor is the temperature the other one is the time. Heating the armor up to lets say 320-360°C for 3-5 minutes, per spot, will have nearly no effect on the hardness of the armor. If you want to feel a difference you need to keep the temperature for lets say 30 minutes at least. (Depends on how high you heat it up, I say 300°C for 30 minutes makes a difference) I could look it up if someone wants to know how it exactly works....


@Pieter B Mathias didn't check the hardness of the pieces, he only took thickness and pictures as well as weight and the dimensions. He didn't have the time and equipment to check every piece. Also the only way to check the hardness leaves a dent in the armor. It 's minimal but some people might have been opposed by the idea. And it is NOT a meaningful result. Even if the one spot has 45HRC you can not say that the hole piece has 45HRC. At least not when it comes to old steel. As the carbon content can vary a lot in one piece.
I 'm sceptical about the method Wiliams used as it is no commonly used/accepted technique and also here you can only check a small part of the armor.
What might work is to x-ray the hole armor compare it to other pieces and with modern heat treated steels, this could work. But would be very expensive.

@J Kemp
you can also let the piece rust for a few weeks and boil it in tea afterwards. Turns out to be a lovely finish:
Burgonet

[Mark Griffin]

If the pigment is available and works in oil or varnish, any is possible. And they don't have to conform to anything heraldic unless needed for something formal.

[Vincent Borg]

I make no claim that what I will describe was indeed used to blacken and rustproof arms and armour;
However, it might be usefull to keep in mind that craftsmen of yesterday were nothing if not highly observant of methods and processes that might improve their artifacts in any way.
And actually building up a layer of dark black oxide on iron and steel, that gives some protection against red rust oxidation is actually very very simple.

Consider how often one comes across well trod manhole covers and iron grates that dont really rust but instead aquire this grey, blue sheen in place of red rust; Or, if you will, how a well used plain carbon steel kitchen utensil, will not really rust but develop a similar patina....I am convinced ( without one shred of historical evidence mind :-) ) that craftsmen of old must have picked up on and made good use of this interesting process.

We are here talking about rust bluing: That is the conversion of red oxide into black iron oxide.
All one needs to do is to first induce a thin layer of red oxide, boiled ( scalding water works too), then brushed or carded off.
The process is repeated until the desired layer of black grey blue oxide is built up.

The water temperature might have a bearing on some steels and the resultant shade. What I can tell you from practical experience is that low temperatures results in a brown hue..

To promote red rust, the modern gunsmith would make use of strong mineral acids, But I have found that a great many natural products can be effective : Tomatoes and grapes, well rubbed in, the piece allowed to stand for a day to "rust", then its scalded off and rubbed with though bristle brush ( steel wool works).
About a year ago a carbon steel folding knife got the treatment from whatever fruit and vegetables were on the kitchen counter. I did not boil the item, but simply held it under a hot water tap for a few seconds in between scrubs.
After about 10 such cycles, the blade wore a nice grey blue patina.
The knife rests in the bottom of my range bag, unoiled and is only used rarely to cut up some target carton a couple of times. It still wears the same hue and no rust.

Like I said, I have no proof at all that this system of blackening and rust was used in days of old.
But, I have more faith in the observant and innovative powers of ancient artisans, than I have of today's hubric academia that often passes for archaeology.