Obsidian bladeIf anyone has earned the right to be a bit nerdy about knives, then it's us. Which brings us to the oft discussed topic of the sharpest blade in the world.

Leaving aside our knives of course, there are many earnest scientific disussions/arguments on the web as to which material makes, or would make the sharpest blade.

The trade off, of course, as we've mentioned already in our article about Samurai swords, is that very sharp blades can be very brittle, and it's no use to anyone if parts of a knife break off while it's being used. So there is an element of practicality as well.

The hardest material out there is diamond, so logically a diamond knife should be the sharpest type. The difficulty is that diamond crystals tend to 'cleave' in what's called an octahedral fashion, which doesn't allow for a very sharp blade cross-section.

Glass on the other hand is 'amorphous', so it does not have any natural planes to split, or cleave to, making it much more suitable for making sharp edges.

A type of naturally occurring glass that has already been in use since the Stone Age as a blade is obsidian. Obsidian is a volcanic glass that is created when magma is pushed to the earth's surface and is cooled very rapidly. This stops it from forming a crystal structure and also introduces a form of 'compressive strength' which makes the material even stronger.

The Mayan Indians are credited with using obsidian blades first 2,500 years ago, although Stone Age spear tips made of obsidian have been found elsewhere in the world. Since obsidian will fracture down to a single atom, it is claimed to have a cutting edge five hundred times sharper than the sharpest steel blade, and under a high magnification microscope an obsidian blade still appears smooth, whereas a steel blade has a saw like edge.

So why aren't we all equipping our kitchens with obsidian knives? Obsidian knives are quite delicate and tend to be a little brittle, so they're probably not your best choice for the rough and tumble of a kitchen, particularly where they might strike something hard. Obsidian is not particularly hard (unlike diamond), it's just capable of being very sharp. Obsidian knives have however been used in medical procedures where very precise cutting is required and where laser surgery is not available.

One of the big advantages of smooth cuts (as one of our customers has already mentioned) is that wounds from sharp blades heal more quickly than more jagged cuts, and are less prone to infection. However, even the manufacturer of the medical-type obsidian blades recommended that 'hard objects should be avoided' and 'twisting or lateral motions should not be employed'. A bit of a hard one to police in the kitchen.

Whether you can sharpen an obsidian blade in one of our Nirey sharpeners is another question. If you have an obsidian blade, perhaps we should put it to the test – will it sharpen?

Image credit: http://commons.wikimedia.org/wiki/File:ObsidianBladeChiapaTuxtla.JPG