Dense Bone Weapons

Simple and short question:

• How much denser would human bones need to be so we can make viable weapons out of it?
• Would increasing the density to the point that it could be used as a viable weapon make it too heavy to wield?

Sealing the bones together is not required. Just assume you have a ten cubic feet sized block of human bone.

TLDR: Could bone ever be dense enough to compete with steel in the weapons business without being too heavy to wield?

• This doesn't make sense. Is the bone weapon a fixed size already? If the bone was as dense as steel and you shaped it to the same size as any steel weapon it would have exactly the same weight as that steel weapon. It's more likely less dense though, so will always be lighter for a similar size. Jul 17, 2015 at 16:58
• Sort of, I have a block of bone with a set volume but variable density, from which I'm crafting a melee weapon (think medieval style) to fight people with steel weapons Jul 17, 2015 at 17:01
• Bone has been used before in human weapons, see this. Granted, these aren't human bones, but there's not too much difference between the bones of land mammals. Jul 17, 2015 at 17:11
• Your stock material has a set size, but you're not wielding that so it's irrelevant. You have several variables: density, weapon size, durability, and desired weight for wielding. It seems the question is no whether it's too heavy to wield, but whether a bone weapon of similar size to a steel one can survive use against steel one, yes? Jul 17, 2015 at 17:13
• Yes and no, more like could a normal bone weapon hold up against steel, and if it can't how much denser (than normal bone) would it have to be before it could. (And once there what is the approximate weight?) Jul 17, 2015 at 17:16

Density is not the problem. Human bone is not particularly dense but it would be easy enough to add weight if more inertia was needed and plenty of weapon designs do not require heavy weight.

The problem with bone as a weapon when compared to steel is:

• Bone is brittle - it fractures
• Bone does not hold an edge

These are the problems that need to be solved, and without solving them density is very much a side issue. In particular a steel weapon is going to cut massive chunks out of a bone one every time they hit each other.

This Question has some interesting information for you too: How advanced or effective weapons can be created from mostly animal body parts?

• Tim I think the OP was mentioning density in relation to how well bone would hold up to steel, not purely for weight reasons. Jul 17, 2015 at 17:52
• The OP mistakes density for strength, hardness, and toughness. Gold, for instance, is 3 times denser than steel, but not an obvious candidate for making swords. Jul 17, 2015 at 19:08
• @James Yes, but density is completely irrelevant for that. This is what I was saying. Jul 17, 2015 at 23:01

Calcium vs Iron, no bet on Calcium

In a comparison of Iron vs Calcium + Phosphorus as a material to make weapons with, Iron is by far the best. Density isn't really the problem, since a 1m^3 block of Ca+P will never ever match the density of Iron, ever. What does matter is the binding properties of the material and what kind of strength is in those bonds. Asking on Chemistry SE will get you a very good answer about why Ca+P is inferior to Fe for weapon and tool making.

Evolution of Weapons on Earth

The earliest weapons on earth were bone or wood. This makes sense because they are easy to come by. Stone tools maintain a better edge but require some manufacturing techniques. Stone was replaced by copper then replaced by bronze then iron then steel. Remember that weapons have an intrinsic evolutionary element to them, so armorers are always looking for superior materials, techniques and shapes to give maximal advantage. The fact that we see an evolution from bone/wood to copper should indicate that the blacksmiths of the time saw that copper was a superior weapon material.

If there is only bone available, use it. If something better than bone is available, such as copper, bronze or iron, use that instead. You'll get a better weapon.

Bone already works fairly well without modifications (think of the scene in 2001: A Space Odyssey where the ape man kills a rival with a femur picked up off the ground...), and our ancient Ancestors were fairly skilled in modifying bone to make awls, using jawbones as a sort of primitive saw or knife and so on.

So long as your opponents are of a similar technological level, then grabbing a bone from a kill will do just fine. Of course when the smart ape on the other side learns how to knap flint....

Bone can be used to make sharp pointed objects line awls and needles, so your tribe could use bone to make fine tips for spears and arrows, although the small points would not be able to cause a lot of extra damage compared to a fire hardened wooden tip of a spear or arrow. You could also use the long femurs of prey animals as the handles for maces, tying rocks to the end to increase the mass and leverage. Even if the handle breaks, you will have a jagged edged thing in your hand which would make an improvised knife. You are already in hand to hand range, so leaping the last bit of distance to stab your victim isn't a big stretch.

The real issue with bone is that it is a composite material, and its toughness is derived from the mixture of calcium held in a somewhat flexible matrix. "Wet" bone is actually tougher than dry bone due to the flexibility of the matrix, but since you need a living organism to ensure the bone is also alive, this makes using it as a weapon in that state somewhat difficult...

I think you'd be surprised at how easy it would be. We design our weapons around the materials we have. Organic compounds, like bone and wood have all sorts of interesting properties. This is why spears, which are primarily made of wood, were effective in eras involving swords.

The most important part is not actually the weapon, but the techniques. Every weapon has things it is designed to do, and things which will fail, or even break the weapon. The techniques one trains warriors in should account for this, and only use the weapon in its strong directions. In the case of bone, its strongest direction tends to be the long direction (simply because of the way long bones get used in a body). As an example technique, I could see warriors using the spikes to deflect a sword from a crossing cut into one which is along the length of the staff. This would be highly counter intuitive for swordsmen who are used to fighting against simple wooden staves without teeth, and that may leave openings for counterattacks.

As for the spike on the end of the weapon? No problem.

• So basically if the wielder changed his technique to accommodate the weapon it would work? Jul 18, 2015 at 2:58
• @HadesHerald Generally speaking, yes. I would not want to face an expert with metal blades such as a samaurai, for they to have changed their technique to accomodate the weapon, but I'd expect an advanced bone weapon to do well enough in its own right. Jul 18, 2015 at 5:56