Too gentle a rubdown leaves contaminants on the surface . Too vigorous a scrubbing erodes the metal itself .
擦拭太过温柔，其表面会留有污染物；用力过猛，又会擦掉金属本身的表面成分。
In addition the beforehand media once reported that the oversized student scratches the leather shoes , to give somebody a rubdown , manicure and so on , can not but say , present 's university students indeed were " the high quality common laborer " .
Importantly , says dr cumpson , unlike a manual rubdown , his procedure can easily be standardised , and the kit necessary to perform it is cheap and widely available , allowing laboratories around the world to keep their own kilogram replicas clean .
