Cleaning Slides and Coverslips

This page describes the method used to clean microscope slides and coverslips before examination and mounting.

Purpose

Even slight traces of grease, dust, dried residue, or detergent can affect the appearance of a specimen under the microscope, especially when examining unstained material or fine surface detail.

The aim of this method is to produce glass that is:

• Visibly clean
• Free from detergent residue
• Free from grease or handling marks
• Dried without streaking or lint

Standard Method

1. First wash in soapy water

Slides and coverslips should first be washed in warm water with a small amount of mild detergent.

Each piece of glass should be gently rubbed between the fingers to remove visible dirt, grease, and residue.

Do not use abrasive cleaners or scouring materials, as these may scratch the glass.

2. Rinse thoroughly

After washing, rinse the glass well in clean water to remove all traces of soap.

Where practical, a final rinse in distilled or deionised water is useful, as this reduces the chance of mineral marks forming during drying.

3. Second pass with isopropyl alcohol

After rinsing, the glass is given a second cleaning pass with isopropyl alcohol (IPA).

This can be done either by:

• Briefly dipping the slide or coverslip in IPA, or
• Wiping it with a lint-free tissue lightly moistened with IPA

This step helps remove remaining grease and encourages clean, even drying.

4. Drying

Allow the glass to air dry in a clean, dust-free place, or dry it gently with a lint-free tissue.

Avoid materials that shed fibres, such as kitchen towel, as these can cling to the glass and become visible during examination.

5. Storage and handling

Once dry, slides and coverslips should be stored in a closed container or slide box to reduce dust accumulation.

They should be handled by the edges whenever possible.

Notes on Coverslips

Coverslips are fragile and easily broken, so they should be handled with particular care.

Although they can be cleaned using the same method as slides, replacement is often preferable if a coverslip remains marked, scratched, or contaminated.

Scope

Unless otherwise noted, observations published on this site are assumed to have been made using slides and coverslips prepared using this method.

Practical Summary

The routine used in practice is:

1. Warm soapy water
2. Thorough rinse
3. Isopropyl alcohol second pass
4. Air dry or dry with lint-free tissue
5. Store clean and handle by the edges

This method is good enough for routine microscopy work.