SECURELY tucked away inside a French vault is a lump of metal known as the International Prototype. A mixture of platinum and iridium, it was made in the 1880s to define the mass of a kilogram.

But work by a team of Australians could help pave the way for the retirement of this century- old prototype, as weight and measurement experts across the globe work towards a more scientific definition of the kilogram.

The project requires the development of perfect silicon spheres, and optical engineers at CSIRO's Australian Centre for Precision Optics — considered world leaders in the craft — are doing their part.