Out of aesthetic curiosity —

In the premodern, preindustrial world, were there any durable methods of achieving a bronze-like finish on tempered steel? Thinking of late medieval/renaissance armor in particular. Not bright gilding — bronzing. Or perhaps coppering...

Do we have any examples?

Regards,
Elisha

I know that heating steel will turn it a goldish-bronze color, but also bluish to purple. That would be a tricky process, though, to get it a uniform color, and the color you want. Maybe a chemical process would be better, but I don't have it. Wish I did..........McM

Plating in bronze would be the only alternate I know. Lots of replica armour, mostly Greek and Roman styles, are bronze or brass plated steel. They seem pretty resilient, and look pretty good to me. KOA sells a ton of it, mostly from MRL. You might check into the plating process they use. ............McM

a modern process to achieve plating one metal over another would be though electrolysis, known as elector-plating. but how far back that process was developed i don't know. being that it involves electricity, it's regarded as a modern process even though it is rather simple to pull off depending on what metals your using.

as Mark points out steel can be heated to give it colors, the straw yellow color is at the bottom the temperature scale for iron/steel, but to achieve this, it would be very hard to get a uniform finish.

There is a blacksmith finishing technique of brushing steel with a brass bristled brush while it is cooling from a colored heat. This deposits a thin layer of brass on the surface of the steel. I haven't personally done it, but it has to be fairly old - historic.
Any of the methods involving heat will affect the hardness of the steel, this would likely completely temper the steel, removing most hardness. The heat treating process is basically heating till bright red and quenching, which achieves maximum brittle hardness. This must then be tempered to whatever degree is appropriate. The tempering process will leave a color due to surface oxidation between yellowish to blue/purple. But this is very thin, and typically not serviceable for heavy use.

Thanks guys.

I'd like to see an armor deliberately colored to straw/browns via heat treatment, though I wonder how that would affect tempering...

- to temper to a straw yellow, this would be a very low temper. normally you think of tempering iron/steel to blue to achieve the correct reduction in hardness. in Jim Hirsoulas's first book, he describes to bring steel to a straw yellow temper 3 times to give a sword a 'spring' like temper. but he also points out that this is depending on the alloy used as others Heat Treat at different temperatures for the best results.

I believe his description is made this way so that you reduce the hardness of the metal in a contorted limitation and gradually as it is very easy to over temper especially if your working on a sword that's taken you months to build and you possibly ruin it during the final process. to temper to blue is the norm (again depending on the alloy used) but the blue is at the high end of the color scale, and lasts over a wider range of degrees than the cooler colors.

between the straw colors and purples there's only about 20-50 degrees difference in heat so getting them to be a uniform color is really hard to do, below here i have an example of some of my heat blueing work. a little craft thing i picked up a while back making flowers from sheet metal. you'll see that i have a 'rain bowed' coloring happening to the rose, i got this by heating the steel to straw yellow, pulled the heat away, and the residual heat from the steel actually turned it to all the natural colors you see here. it may be easier to pull off a uniform straw yellow on just a single sheet of steel, but still really tricky.

and just as Dave points out, this finish is very light, you can scratch it off very easily.

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Pretty. Wonder if a good treatment of urushi would keep the heat finish on for a bit.

Anyone know what kind of temperature is required for brushing on a layer of brass?

According to post #5 here, 400-800 deg F. What is described as a "black heat".

http://www.iforgeiron.com/topic/31700-brushed-brass-finish/