Laboratory Glassware: What do the calibration classes mean and which is right for you?

Our volumetric laboratory glassware is available in three main calibration classes: Class AS, Class A and Class B. Below is a quick guide to what each class means so you can better decide if they are suitable for your application.

The accuracy of each class is measured in terms of tolerance (tolerance is the accuracy in a measurement made with the glassware). Class A and Class AS volumetric glassware have a lower tolerance than Class B and therefore can be considered more reliable and more accurate (generally to two places after the decimal point).

Classes

Class A/AS:
Graduation: Ring marks at major graduations
Volumetric instruments of class A/AS are within the error limits defined by DIN and ISO and carry the DE-M marking standards.

• Example for 250ml CLASS A Glass Cylinder = Permissible variation error @ 250ml +/- 1.0ml

Class B:
Graduation: Short graduation marks
Volumetric instruments of class B are within twice the error limits when compared to class A/AS as defined by DIN and ISO standards.

• Example for 250ml CLASS B Glass (or Plastic) Cylinder = Permissible variation error @ 250ml +/- 2.0ml

Calibration

Each glass volumetric measuring instrument in Class AS and Class A is individually or batch calibrated. Computer-controlled systems ensure maximum precision in a fully automated production line.

Each glass volumetric measuring instrument in Class B is batch (not individually) calibrated. Computer-controlled systems ensure maximum precision for the batch of glass instruments in that particular production line.

Types of calibration

'TC, In':
The contained quantity of liquid corresponds exactly to the capacity indicated on the instrument (eg., graduated cylinders and volumetric flasks).

'TD, Ex':
The delivered quantity of liquid corresponds exactly to the capacity indicated on the instrument (eg., pipettes and burettes).

Heating of volumetric instruments

All glass volumetric instruments can be heated up to 250 ºC in a dry box or sterilizer without having to worry about a change in volume. Use only gradual heating and cooling. Abrupt temperature changes can cause thermal stress and may result in glass breakage.

Glassware for research organisations and pharmacies

When purchasing measuring and volumetric glassware for applications where high accuracy is required, Class A and Class AS stamped glassware is always recommended.