Laboratory

Recommendations for proper handling and cleaning of check weights according to the OIML classification

Tuesday, 05.07.2022. - 12:00

Do you know what the accuracy of your weights depends on? Weights are used daily for testing and calibrating scales, so they should be treated with special care. Even the smallest changes to the weights, such as dust, grease caused by fingerprints or temperature fluctuations, can affect their accuracy. To ensure the accuracy of your weights, below is a list of factors to consider when handling, storing and cleaning check weights.

A higher class of weight accuracy requires more careful handling

It is important to handle check weights properly and maintain them regularly, in order to prolong their life cycle. Any damage to the surface of the weight or any form of corrosion, dirt, moisture, fingerprints or mechanical wear can affect the (in)accuracy of the weight.

When handling check weights, it is also important to take into account: the maximum permissible errors for the accuracy class of the weights, their material properties, surface characteristics, environmental conditions and frequency of use. It is especially important to take care of the weight's accuracy class because here applies the golden rule - the higher the weight's accuracy class, the more carefully you have to handle it.

It is also advisable to calibrate weights regularly by authorized and reliable calibration service providers. If you are looking for a quality calibration service with a high level of accuracy, you can calibrate weights in our calibration laboratory accredited according to the HRN EN ISO/IEC 17025:2017 standard.

What should you avoid when handling weights?

  • pulling or pushing weights over support surfaces (e.g. weighing surfaces or weight storage platforms)
  • touching OIML class E and F weights only with fingers
  • contact with sharp or rough objects
  • work in high humidity conditions
  • dust or dirt from the glue
  • contact with aggressive media (e.g. bases and acids)
  • static electricity
  • strong magnetic fields

Tips for handling control weights

Never touch the weights with your fingers, but use the corresponding tools!

In accordance with the international recommendation OIML R111 1-:2004, section 14, tools used to handle the weights must not damage or change the surface of the weights during use.

Handling OIML class E1 weights

To handle OIML class E1 weights, we recommend the use of carbon-tipped forceps, weight forks, weight pliers or lifting devices from our range of control weights and weight sets
of accessories.

Handling OIML class E2 and F1 weights

For handling weights according to OIML classes E2 and F1, we recommend using the following tools:

  • for weights < 1 kg, use only tweezers with protected tips (special silicone or carbon)
  • for weights ≥ 500 g, use weight forks, weight pliers or lifting devices
  • for weights ≥ 1 kg, cotton gloves are sufficient.

Handling OIML class F2 and M1 weights

For handling weights according to OIML classes F2 and M1, we recommend using the following tools:

  • for weights < 1 g, use only tweezers with protected tips (special silicone or carbon)
  • for weights ≥ 1 g, be sure to use tweezers with protected tips (special silicone or carbon) or wear cotton gloves
  • for weights ≥ 500 g, use weight forks, weight pliers or lifting devices
  • for weights ≥ 2 kg, cotton gloves or fine leather gloves are suitable.

Handling OIML class M2 and M3 weights

For handling weights according to OIML classes M2 and M3, we recommend using the following tools:

  • for weights < 1 g, use only tweezers with protected tips (special silicone or carbon)
  • for weights ≥ 1 g, use only tweezers with protected tips (special silicone or carbon) or wear cotton or leather gloves
  • weights ≥ 500 g and colored cast-iron weights can be handled with bare hands as long as the latter are clean and dry.

Tips for storing weights

Always store the control weights in the designated place!

In accordance with the international recommendation OIML R111 1-:2004, section 14, weights must be stored in appropriate boxes, except for weights of classes M1-2, M2, M2-3 and M3.

Before use, weight and mass standards must always be visually inspected for contamination such as dust, fingerprints or other surface changes such as corrosion, foreign matter, etc. If necessary, use a magnifying glass or microscope to assist in this task.

Storage of OIML class E1 weights

OIML class E1 control weights should be stored in glass bell jars. We recommend using a dust-free storage location within an air-conditioned laboratory, preferably in a lockable laboratory cabinet. Before using the weight, check whether the temperature of the weight is adapted to the environmental conditions at the weighing location. Transport boxes should only be used outside the laboratory.

Storage of OIML class E2 and F1 weights

OIML class E2 and F1 weights should be stored in glass bell jars or in suitable containers (cases). Holes and slots in weight boxes must be lined with a soft, lint-free material.

Before using the weights, check whether the temperature has adjusted to the environmental conditions at the weighing location. To achieve temperature equilibrium, open the weight boxes or take them out of the box.

Storage of OIML class F2 and M3 weights

Weights < 500 g should be stored in suitable containers (cases) such as plastic containers with screw caps.

OIML class F2 weights with a nominal value > 500 g must be stored in suitable containers. Weights with nominal values > 500 g, such as cast iron weights, can be stored in suitable clean areas and do not necessarily need a container. In order to prevent contamination, large weights should still be covered with appropriate protection or foil. Before using the weights, check whether the temperature of the weights is adapted to the environmental conditions at the weighing location. Avoid condensation when using weights.

Tips for cleaning control weights

Choose cleaning agents carefully as they can change the properties and surface of the weights!

How to clean class E1 weights?

To remove dust particles on weights with a nominal value < 1 g, you can use steam from a bellows or a brush. The brush can also clean weights with a nominal value > 1 g. If the weights need to be cleaned with liquids, such as pure alcohol, distilled water or other solvents, this can significantly change the weight value of the weights.

The removal of fingerprints with a cotton or microfiber cloth from weights with nominal values < 100 g must also be evaluated, since the calibrated mass values may change.

How to clean E2 and F1 weights?

Slightly sticky particles of dirt and dust must be removed using a bellows or a brush.

For weights with nominal values > 50 g, fingerprints and minor surface contamination can also be removed with a cotton or microfiber cloth. Removal of wet or sticky objects must be evaluated as it may lead to changes in mass values.

If the weights need to be cleaned with liquids, such as pure alcohol, distilled water or other solvents, this can significantly change the weight value of the weights.

How to clean F2 and M3 weights?

Slightly sticky particles of dirt and dust can be removed with compressed air, steam bellows or a brush. Contaminated surfaces (fingerprints, wet or sticky objects that have stuck) can be cleaned with dry or damp cotton or microfiber cloth.

If the weights need to be cleaned with liquids, such as pure alcohol, distilled water or other solvents, this can significantly change the weight value of the weights. You should be carful when cleaning painted surfaces; do not use substances that will corrode the final paint.

Any layer of oxidation (rust) and damage to the finish paint will generally affect the weight value of the weights. After removing gross dirt, corrosion or loose layers of paint, the weight must be recalibrated.

Can I use the control weights immediately after cleaning?

It is not recommended to use the control weights immediately after cleaning. Based on the recommendations described in the International Recommendation OIML R111-1:2004, Appendix B.4, the waiting time after cleaning each weight class is listed below.

OIML classificationE1E2F1F2 to M3
After cleaning with alcohol7 - 10 days3 - 6 days1 - 2 days1 hour
After cleaning with distilled water4 - 6 days2 - 3 days1 day1 hour
After cleaning with a cloth1 day3 - 4 hours1 hourImmediately
After cleaning with a brush or bellowsImmediatelyImmediatelyImmediatelyImmediately

If you are interested in more details about Sartorius check weights, you can find information at the following link:

Catalog of weights and sets of weights