Recommended Posts

The National Museum of Korea has a set of stone molds for casting blades that would then be hammered out.  Sectioning and then etching and then using a metallographic microscope can show some of the processes used to form a historic blade,  You might ask on the archaeological metallurgy mailing list for cites on such examinations.

Starting from bar stock and hammering out is a waste of time; there is a limit to the amount of work hardening you want/need for the edge.

Share this post


Link to post
Share on other sites

Dear Andrew,

I had always thought that lead was added to modern brass or bronze for ease in machining, not an issue in the ancient world.  That is why many bronze alloys such as brazing rods are forgable and most brass is not.  I don't think that lead would be a natural alloy in copper deposits.  I'm not so sure about tin.

Share this post


Link to post
Share on other sites

It seems that lead was deliberately added in the past to help the castings flow better into narrow sections.

tin had to be mined separately and it was alloyed to make the classic bronze

Share this post


Link to post
Share on other sites

Yes, the ore chemistry of tin and copper is very different (IIRC, my geochemistry and ore deposition classes were about 50 years ago).  I have always wondered how the idea of alloying together two very different metals, one pretty uncommon (tin deposits are less common than copper) came about.

Share this post


Link to post
Share on other sites

There is a lead bearing tin ore; but I don't know if it was known/used in antiquity.  Now the arsenous copper ores were known and used and known to produce a harder copper, (and to be more toxic to process IIRC) Tin/Copper alloys could be very nice indeed with hardness even or better than early wrought irons; but as mentioned Tin is fairly rare; Iron shows up most everywhere in some form---and when quench hardening was discovered then the hardness of steels was MUCH greater than that of copper alloys.

Share this post


Link to post
Share on other sites

Not to mention that bronze is heavier, per cubic volume, than most steels. Not usually an issue for decorative work, but definitely of importance for weapons and armor.

Share this post


Link to post
Share on other sites

Yeah, i measured the density of the bronze as I cast it, to help me get an idea of the amount to melt for the casting, it was approx 8.7g/cm3 which is quite higher than steel between 7.7-8g/cm cubed. 

Testing recently revealed I didn't harden the edges sufficiently as it rolled in one spot, so I made a better jig for hammering them, and now it is much better.  I'll attach a picture once I take some

Share this post


Link to post
Share on other sites

Question:  It appears that the area that you are hammer hardening is pretty narrow, maybe 2-3mm.  How did you decide on that width?  Or are you taking several passes along the edge so that your total hardened area is wider than the area between the metal pieces in your jig?  Nice set up, by the way.

Share this post


Link to post
Share on other sites

I took a few passes along the blade, the total width of the hardened area is approx 5mm I think, past that point I don’t think there is much benefit as the hardness of the cutting edge is what makes the largest performance improvement

Share this post


Link to post
Share on other sites

Not if the edge rolls 6mm in. 

I tend to think bronze was a discovery rather than an invention. Suppose a bloom(?) type furnace were built with tin bearing rocks? The legend of the almost magically strong hard copper being made by the monks on "stymy" mountain is born. Eventually someone would discover the super copper only happens when THIS kind of rock is used in the melter. Further tinkering refines out tin and THEN experiments with alloys begin.

Frosty The Lucky.

Share this post


Link to post
Share on other sites
8 hours ago, Frosty said:

Useless excessive quoting removed

I think you are underestimating the material, it is hard enough that it won’t roll that far back unless it was exceedingly thin

Share this post


Link to post
Share on other sites

Differentially hardened edges are often based on failure modes where having a fairly small area prone to chipping out is considered a good thing allowing you to repeat the work hardening to create a new edge where the failed section was.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now