Copper and it's alloys are often overlooked and underestimated.  Some copper alloys can reach strengths comparable to hardened steel, and these alloys are used for tools in hazardous environments where sparks would be very bad. 

I'll have to look and see, but most bronzes are hardnened by hammering/cold working.  I've seen pictures of Egyptian cold worked straight razors made of bronze and copper.  Modern bronzes may be heat treatable for hardening, but it will depend totally on the alloys besides copper and tin.  Lead is added to modern brass, among other things, for easier machining.  I can see how it would make hammering easier, but I'd think it would have undesirable effects on anything intended to have an edge or point. 

As much as I hate to use it for reference, "Deadliest Warrior" shows the strength of bronze when a ninja's steel kama fails to penetrate a bronze breast plate. 

It's fairly common for an adding an alloying element to bring down the melting point of the total alloy.  In cast iron, the melting point is lower than any of the individual components, iron, silicon, or carbon.  This is not the case for bronze, but it can happen in other alloys.

I don't think I've ever heard of cold forging a sword from steel that's already hardened (quenched and tempered).  If one has the heat to hot forge steel, one has the heat to reharden the steel afterward.  I've had hardened steel cold forge my hammer faces, not the other way around.

Hallo wannasling!
First, your Maori war club is something really wonderful! My best congratulations for your efforts, you show talent! Second, I've rapidly seen your link, and it seems interesting; I'll watch out it carefully as I'll have more free time!
And then: non-fired clay will not work. The heat of the flow will cook the clay, and the sudden change of temperature will lead to breaks and maybe explosions. Then I imagine that the bronze will encounter some difficulties to flow in. The process you described is 100% correct, you'd just need to fire the clay. But, since you can't do that, I'd use plaster insted. In fact, it was the first think I thought about while I was reading your post, and I encourage you in using that, even because you've already done this and are quite experienced in it. Go for it, you can always begin using clay once you've got your bronze sword  and, as I've told to another forumer, I don't think that clay molds are the best way for making a sword: for such a long item, I'd prefer to use stone molds, which can be worked and modified much easier.

And now, to me2:
you're right, hammered bronze is almost as strong as steel, just a pair of level below in the strength scale (just think that, in the XIV and XVth Centuries before Christ, cannons were made of bronze).
Cold hammering a bronze edge is suitable only if there's more percentage of tin there; since one can't know this, it's recommended to heat the edge moderatly, to avoid the risk of breaking it. The alloy will not break, but the edge will neither; it's just a measure of precaution.
I was not talking about cold forging a steel sword, I told to work it out, giving it the shape of a sword and its edges. One can forge only with heat and sure, one can forge steel, and then reharden it, but forging it you change its molecular disposition, and risk to not be able to recreate it. That's why I've suggested to cold work the truck springs 
Greetings,
Mauro.

Hallo! You reserved these words 
About concrete, I don't know about its exact composition, and I have never thought about it as a mold. But I think that clay has a similar composition, so I'd give concrete a try. To avoid injuries from an explosion, take some precautions, for example pre-heat the molds, use long tongs to put in the bronze (so you can put more distance between you and the molds), wear glasses and a sturdy body protection (for example, put a pair of sweaters on and then a leather jacket). Then I suggest you to try with a small mold, first, and use it twice or three times, to see if it works without any big danger.
Anyway, If it survives to the pre-heating, it's a good sign, because, if it has moisture inside, this should provoke come cracks. If there're no cracks after the pre-heating, then it will be good to be filled with bronze. Remember that a good pre-heating last at least for 10 minutes, and should start with the molds at a certain distance from the fire, and then move them closer and closer to it.
I'm sorry, those're the only information I can give you, because I really don't know how it will work. But I feel confident that it should work, so try it, just remember to take some precautions.
And keep me informed on how it's going!
Greetings,
Mauro.

Oh well... so don't use concrete wannasling 
Thanx me2!
Mauro.

An open mold would work fine if you plan to make axes or chisels, or even daggers or short swords, but beware: an open mold don't allow your blade to have the central.... rib? is this the correct word? so it will be a somewhat weak blade when it comes to fight.
BUT you can do a lot of jewelry with open molds, if you're interested in it I've got some tips for making it easily 
Greetings,
Mauro.

This was the the thread that convinced me to join this forum, congrats
Wanasling, nice Maori club, too bad they didnt get to bronze age.
Although, with a bit of prompting, they could have got to iron age in my area, im sure of it......

Er.... where're you from? 
Mauro.

Mauro Fiorentini wrote on May 22^nd, 2011 at 7:20am:


New Zealand. The Maori are the native people of my land. I live in the Taranaki provence.
So plenty of hard woods and most importantly, Massive reserves of magnetite ore in sand form on our beaches.Worth a few hundred billion i think.
Unfortunatly, cows are an introduced species, so leather belows are out
But hey, if theres a will, theres a way....