Equipment

How To Clean and Maintain Precision Balances and Analytical Balances

4/22/20
Grainger Editorial Staff

Measuring mass is an important part of laboratory work. Specialized balances allow researchers and technicians to do this work with accuracy and precision. When deciding which type of balance to use in the lab, the question of precision is key. More precise balances produce measurements with more digits to the right of the decimal point (also known as significant figures). The precision of a balance depends on its resolution, which is the smallest increment in applied weight that the scale can detect and display. Resolution is usually given in grams, and is sometimes called readability or division.

A Procedure for Cleaning Laboratory Balances

Mettler Toledo has published a standard operating procedure for cleaning laboratory balances, including precision and analytical balances. This document includes the following general “do’s and don’ts,” along with other helpful recommendations:

First, remove powder and dust from the balance. Use a tissue to do this, rather than trying to blow the dust off of the instrument, which could unintentionally move dirt or other materials into the balance.
After any powder and dust is gone, remove sticky substances using a damp, lint-free cloth and mild solvent such as isopropanol or ethanol 70%. Don’t use abrasives, and don’t spray or pour liquids onto the balance.
When wiping or brushing the balance, wipe away from the opening where the pan sits and away from any air ducts, which are gaps in front of or behind the draft shield.
When parts can be removed without tools (as described in the balance’s operating instructions), remove them for cleaning.
Keep peripheral devices connected if possible and clean the balance in its working location.
After cleaning, reassemble the balance and turn it on (with enough warm-up time) to make sure that it’s working.
Level and calibrate the balance, check for accuracy using a test weight and test printers and any other connected accessories.

These general tips are a great starting point, but be sure to check the operating instructions of your specific instrument, which may offer more detailed guidance for questions like which cleaning products to use. For example, while Mettler Toledo recommends cleaning with mild solvents, other manufacturers, such as Kern, advise against using solvents and instead recommend only mild soap suds.

Also, manufacturers’ operating instructions will describe how best to disassemble any parts that can be removed for cleaning.

How Many Types of Lab Balance Are There?

Laboratory balances can be divided into a few basic categories based on precision and resolution. In increasing order of precision/resolution, there are precision balances, analytical balances, semi-micro balances and micro balances.

How Precise Is an Analytical Balance?

Precision balances, which are also called top-loading balances or ordinary balances, offer between zero and three digits to the right of the decimal point, depending on the model. Analytical balances offer four or more digits to the right of the decimal point. At this level of precision, it becomes necessary to enclose the weighing pan to help eliminate the effect of air currents on the measurements, according to “Analytical Chemistry for Technicians.” Semi-micro balances offer five digits to the right of the decimal place. Micro balances offer even higher levels of precision.

Why Is It Important to Keep a Balance Clean?

It’s important to keep laboratory balances clean, especially the more precise analytical balances, because spills can react with the surfaces of these sensitive instruments, which can affect the accuracy of their measurements, according to “Analytical Chemistry for Technicians.” Spilled chemicals or debris can also potentially contaminate the samples that are being weighed.

How Do You Clean an Analytical Balance?

Cleaning an analytical balance involves removing the draft shield that protects the weighing pan from the influence of air movement. According to Mettler Toledo’s standard operation procedure, you should first remove any dirt surrounding the unit, and then unlock and remove the draft shield panes, followed by the inner draft shield and any other removable parts on the balance, such as the weighing pan, pan cover, pan support, wind ring and drip tray. These removable parts can be cleaned with window cleaner or other mild cleaning agent containing ethanol, or they can be cleaned in a dishwasher.

The information contained in this article is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This article is not a substitute for review of current applicable government regulations, industry standards, or other standards specific to your business and/or activities and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.