Micro Cover Glasses for Microscope – Square, Circular and Rectangular

Quick Answer: Micro Cover Glasses for Microscope are very thin, flat pieces of glass laid over a specimen on a microscope slide, supplied in square, circular and rectangular shapes. Micro cover glasses flatten the mount, hold liquid in place and protect the objective lens from the specimen.

What the Cover Glass Does

A cover glass has three jobs. It flattens a wet mount into a thin, even layer so the whole field comes into focus together; it slows evaporation and stops the liquid spreading across the slide; and it keeps stain and water off the front lens of the objective. In permanent preparations it also seals the specimen under a mounting medium so the slide can be used for years.

Thickness matters more than most users realise. High-power dry objectives are designed to look through a cover glass of a set thickness, commonly 0.17 mm, and a much thicker or thinner glass softens the image at high magnification. Cover glasses are graded by thickness number, with No. 1 and No. 1.5 the grades most used in teaching and routine labs. The listing names only the shapes, so state the thickness grade and sizes you need when ordering.

Each shape has its own jobs. Square glasses cover a routine wet mount such as onion epidermis or a drop of pond water. Circular glasses are used where a round well or dish is involved, for example when cells are grown on a cover glass in a culture dish. Rectangular glasses cover long specimens: blood smears, sections cut on a hand microtome, or several sections laid on one slide.

Specifications

Applications

• Wet mounts of onion epidermis, cheek cells, yeast or pond water in school practicals
• Permanent mounts of sections and smears with a mounting medium
• Covering blood smears and long tissue sections with rectangular glasses
• Growing cultured cells on circular glasses in dishes for later staining

Care & Handling

• Pick micro cover glasses up by the edges with fine forceps; fingerprints on the glass appear as smears in the image.
• Lower the glass at an angle from one edge with a mounted needle, so air is pushed out instead of trapped as bubbles.
• Put used and broken cover glasses in a sharps or broken-glass container, not the general bin.
• Keep the box closed and dry, because damp glasses stick together and are hard to separate.

Why Choose LabEquip

Cover glasses are a consumable that every microscopy lab reorders, from school biology rooms to pathology teaching labs. They are listed in the Microscope & Optics range with slide storage and staining items; list the shapes, sizes and quantities you need on the contact page.

Frequently Asked Questions

What thickness of cover glass should I use?

For general teaching and most high-power dry objectives, No. 1.5 glasses, about 0.16 to 0.19 mm thick, match the thickness the objectives are designed for. No. 1 glasses are slightly thinner and are also widely used for routine work.

How do I avoid air bubbles under the cover glass?

Put a drop of liquid on the specimen, touch one edge of the cover glass to the slide beside the drop, and lower the other edge slowly with a mounted needle. The liquid spreads ahead of the glass and pushes the air out.

Can cover glasses be cleaned and reused?

They can be washed in detergent, rinsed and kept in alcohol for reuse in simple wet mounts, but they are so thin that many break in handling. Most labs treat them as consumables and use fresh ones for stained or permanent preparations.

Which shape should I use for a blood smear?

A rectangular glass is usual, because it covers the long feathered edge of the smear where cells lie in a single layer. Many smears are examined under oil without a cover glass, but a covered smear keeps longer.

How do I stop a wet mount drying out during a long practical?

Seal the edges of the cover glass with a thin ring of petroleum jelly or nail varnish, or use a slightly larger glass. A drop of water added at the edge also tops up a mount that is starting to dry.

Why does my high-power image look hazy even when focused?

Common causes are a cover glass that is too thick, mountant smeared on top of the glass, or a glass tilted over a lumpy specimen. Use the correct thickness, keep the top surface clean and make the specimen thin enough to lie flat.

Last Updated: September 2026