Shortterm instability  possible mistake   What is known specifically about the IPK is that it exhibits a shortterm instability of about  g over a period of about a month in its aftercleaned mass  from what I think is the BIPMs source for this httpwwwbipmorgutilsenpdfMonographieENpdf it seems to be more like  g over a period of about four months for the IPK figure  in that document The proceedings linked in footnote  give no source for the much higher value