Screw-knob weights: Weights in this category are usually cleaned by wiping with a soft non-abrasive material such as high-grade cheesecloth, free from oils or other substances that would leave a residue of any kind on the surface. Occasionally, a weight will have foreign matter adhering to it that requires cleaning by using solvents, applied with a cloth. Ethyl alcohol is a good general solvent. If alcohol does not remove the foreign material, other solvents may be used. Alcohol is then used to remove any film left by the other solvents. Weights with internal cavities should not be immersed in the solvent to avoid the possibility that the fluid will penetrate the opening.


Daily/Periodic Cleaning: (Non-sheet metal weights) Before each use clean all weights with a camel hair or other suitable soft brush to remove any particles that might have settled on the weight. Remember to pay special attention to the bottom surfaces, since these tend to be overlooked. One may also use a syringe bulb or compressed air to remove loose particles. If compressed air is used, especially if it comes from a can, the temperature of the weight may be affected, and the weight should not be used for at least 4 hours to allow the weight to return to thermal equilibrium with the environment. If particles are not removed easily, spot cleaning may be necessary.


Spot Cleaning: Spot cleaning is recommended when foreign matter is observed on weights that cannot be removed using daily/periodic cleaning methods. Use cheesecloth dampened with ethyl alcohol and gently rub the weight surface in order to remove any residual or stubborn debris from the weight surface. If using alcohol does not remove the foreign debris, repeat the process using other solvents such as window cleaner or distilled water. If solvents other than distilled water and alcohol are used, the weights should be cleaned again using alcohol to remove any residual solvent from the weight. For sheet metal weights or other weights made out of aluminum, alcohol should never be used since alcohol can deteriorate aluminum. After spot cleaning, OIML Class (F2 to M3) weights should not be used for a period of at least 1 hours in order for the weight to return to thermal equilibrium with the environment.


References:

  • OIML R111-1:2004 International Recommendation, Annex B.4, describes for how to clean weights correctly.
  • NBS IR 74-443 Weight Cleaning Procedures
  • NIST GMP No 5 Weight Cleaning Procedures (1986)
  • Manufacturers Guidance see website: Troemner / Rice Lakes / Sartorius