Hello all.

I was thinking of taking foundry again next semester and maybe making a bronze sword if the professor will allow it. He says that the course uses Everdur, C.D.A. No. 873, 95 percent copper, 4 percent silicon, 1 percent manganese. Is this a decent material for a blade of about a foot long? I recall that when I was de-gating sculptures last year, it seemed very easy to cut and grind.

There are plenty of original blades with less than 12 percent tin! I wouldn't call it "soft" at all. If I'm remembering correctly, artifacts with over 15 percent tin are pretty uncommon. There is a Mycenaean sword that has only 4 percent, but yeah, that's pretty low!

I don't know what silicon does for hardness, though judging from Timo's list it looks decent. Certainly modern silicon bronze is one of the options used for various repros these days, though I'm thinking sheet metal items. (It would be a great step up from the yellow brass that Indian companies are stuck on!)

Matthew

Yellow brass is only about 50 Brinell hardness; Everdur is a big improvement on that.

For Chinese bronze weapons, a lot of the early ones are 8-12% tin (later ones tend to be 15-20%, which is higher than usual for European bronze blades). So people used bronzes of similar hardness to Everdur for weapons that saw real-world use.

Thanks everyone.

So it sounds good. I'll pencil it into my calendar.

Here's a fun thought: The material fee pays for a certain number of pounds of metal. A dagger would use somewhere around one pound, so there's gonna be plenty left over. If I finish and sell everything else I make, the course might actually pay for itself.

Remember also that the edges of copper based blades or bronze where work hardened at the edges before being given a final sharpening.

What I don't know is how the edge work hardening is done and when one knows when to stop hammering before the edges becomes too brittle or breaks off.

If you do hammer harden the edges you might be able to sharpen it to almost a razor edge, but being bronze it will dull more quickly if used to cut anything too abrasive: But a sword or dagger only needs to cut well for weapon usage and one would not use it to cut other things like a tool knife: A weapon is carried a lot but used rarely so it would remain sharp until needed.

A bronze edge probably needs to be resharpened or realigned with a steel more often than a steel knife.

Hm... didn't think about edge-hardening. I know it's a step in finishing bronze blades, but it didn't occur to me that silicon bronze might not harden at the same rate as tin. Will have to do a bit more research.

It's a good idea, but I'm not certain I could convince them to let me try. They keep all the reusable scraps locked in a drawer until pour days, and you know professors sometimes feel the need to stick fast to the rules.

I don't think I could cast a blade just for testing. The pours are a group effort and each item adds a lot of work that everyone has to help with. Plus each mold takes a couple weeks out of only a four-month semester and uses up some of the limited amount of slurry. Test-hardening would probably have to be on scraps of a suitable size and thickness, if there happen to be any around.

You could buy some tin fishing sinkers at someplace like Walmart and add them in during the melt. Just stir it a bit. The silicon will assure a smooth pour.

Okay, bad news. I got a reply back from the professor today, and the college definitely does not allow us to make weapons, even blunt, unfinished ones.

I might look into farming work out to a professional foundry some day in the future, but they're awfully expensive.