No , there is not going to be an increase in the weight due to some (much desired by critics) mistake of scientists' calculations. We are talking about the standard kilogram , the International Prototype Kilogram (IPK) kept at International Bureau of Weights and Measures. According to researchers at Newcastle University, the 39mm tall and diameter possessing platinum-iridium alloy cylinder, defined as 1 Kg, by measuring hydrocarbon build up on similar surface using a Theta probe XPS (X Ray Photoelectron Spectroscopy) machine, is expected to have gained tens of micrograms since its being defined in 1875.
It isn't the change that matters , its the difference that is expected to be seen among the 40 replicas of IPK distributed around the world. The increase is different for them all, thus creating discrepencies, though small, but could be important in case of international trade of wastes or items where each microgram holds value, as in radioactive substances.
This build up can be, as it has been observed, removed by giving the standard a 'suntan', that is exposing to UV and ozone. It has been suggested since long to redefine the kilogram, along with other standards, in reference to the Planck constant, a fundamental constant of quantum physics, which would add weight to the Kilogram too, and be much more accurate and standardized.
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