Which coverslip thickness grade should I use?

Coverslip thickness is graded as No. 0, No. 1, No. 1.5, No. 2 and No. 3, corresponding to roughly 0.085 to 0.13 mm, 0.13 to 0.16 mm, 0.16 to 0.19 mm, 0.19 to 0.23 mm and 0.25 to 0.35 mm. No. 1.5 is the standard choice for most transmitted light microscopy and for high numerical aperture objectives, because the optical design of most 40x and 100x objectives assumes a 0.17 mm coverslip. Using No. 1 or No. 2 instead shifts the plane of focus and degrades resolution and edge sharpness. Choose No. 1 where the coverslip has to be thin for very short working distance condensers, and No. 1.5H, which is the tighter half of the No. 1.5 range, for demanding imaging and confocal work. Thicker grades are used where mechanical strength matters more than optical performance, for example when a wet preparation is being pressed or handled repeatedly.

Aqueous or resinous mounting medium?

Match the mountant to the stain and to how long the slide must last. Aqueous and non-setting mountants are water miscible, so they are used with stains that would be damaged by alcohol and clearing agents, such as immunofluorescence, enzyme histochemistry, some special stains and any preparation that must stay hydrated. They are quick and gentle, but they do not harden, so the coverslip must be sealed with nail varnish or a similar rim seal, and the slide has a shorter working life. Resinous mountants such as DPX, Permount, Entellan or Canada balsam are dissolved in a solvent, harden to a permanent glass-like film with a refractive index near 1.5 and give long-term archival slides with high contrast. They require the section to be fully dehydrated and cleared, because any residual water produces a milky, cloudy preparation. When a slide must survive years of retrieval and re-examination, use a resinous mountant and a properly cured slide.

Why do my mounted slides show bubbles or milky patches?

Bubbles come from trapped air and are avoided by lowering the coverslip slowly from one edge, letting the mountant spread by capillary action, and using enough medium that the coverslip floats into place rather than being pressed down. Milky or cloudy patches in a resinous mountant almost always mean residual water or incomplete clearing: the section was not fully dehydrated through the graded alcohols, or the clearing agent was saturated or water contaminated. Trapped solvent that later evaporates produces shrinking and retraction of the medium from the section, which is why a slide should be left flat to cure before it is filed upright. Over-thick mountant, too much medium under the coverslip, spreads beyond the glass and glues the slide to the next one in the box; use a minimal volume and wipe the edges with a solvent-damp cloth before the medium sets.

What coverslips and mounting media does JWRESEARCH supply in Singapore?

JWRESEARCH supplies coverslips and mounting consumables in Singapore, including square, rectangular and round coverslips in thickness grades No. 0, No. 1, No. 1.5, No. 1.5H and No. 2, pre-cleaned and plain glass formats, chamber slide and coverslip options for culture work, resinous mountants such as DPX and xylene-based media, aqueous and non-setting mountants, fluorescence anti-fade mounting media with and without DAPI, rim sealants, slide boxes, drying racks and mounting accessories such as forceps, slide holders and blotting pads. We stock the common sizes and pack counts and can supply bulk quantities for high-throughput histology laboratories. Orders are dispatched locally in Singapore, with volume pricing for hospitals, diagnostic laboratories, research institutes, universities and industrial quality-control laboratories.

Coverslipping and Mounting Media Singapore

Published: {{NEW_ARTICLE_DATE}} | By JWRESEARCH | Category: Histology & Microscopy

A section can be perfectly cut and beautifully stained and still fail at the last step. Coverslipping is where the work is either preserved or ruined: the wrong mountant turns a crisp preparation cloudy, the wrong coverslip thickness costs resolution at high magnification, and a slide left to cure on its side leaks medium into the rest of the box.

At JW RESEARCH SUPPLY, we supply coverslips, mounting media and the accessories that go with them to histology and microscopy laboratories across Singapore. This guide covers how to match the glass and the medium to the stain, and how to finish a slide so it is still readable in five years.

Coverslip Grades Compared

Grade	Thickness	Optical Use
No. 0	0.085 – 0.13 mm	Very short working distance condensers, special applications
No. 1	0.13 – 0.16 mm	General brightfield, low to mid magnification
No. 1.5	0.16 – 0.19 mm	Standard for 40x and 100x objectives, 0.17 mm nominal
No. 1.5H	0.17 – 0.19 mm	Confocal and demanding imaging, tight tolerance
No. 2	0.19 – 0.23 mm	Robust handling where optical quality is secondary
No. 3	0.25 – 0.35 mm	Mechanical protection, wet preparations

Most objectives are corrected for a 0.17 mm coverslip thickness. No. 1.5 is the closest standard grade, which is why it is the default for high numerical aperture work. If resolution looks soft at 100x and the optics are otherwise fine, check the coverslip grade before blaming the objective.

Mounting Media Reference

Medium	Refractive Index	Sets Hard	Typical Use
Aqueous, non-setting	1.33 – 1.44	No, needs rim seal	Enzyme histochemistry, some special stains
Glycerol or glycerol-PBS	1.44 – 1.47	No	Immunofluorescence, temporary wet mounts
Anti-fade fluorescence medium	1.42 – 1.47	Varies, often cures	Fluorophores, with or without DAPI
Resinous, DPX or similar	Approx. 1.52	Yes	Routine H&E and archival slides
Canada balsam	Approx. 1.53	Yes, slowly	Traditional permanent preparations
UV-curing mountant	1.48 – 1.52	Yes, on light exposure	Fast batch coverslipping

Specification Reference

Parameter	Typical Value	Notes
Coverslip formats	18x18, 22x22, 24x24, 24x50, 24x60 mm, round 12 – 18 mm	Match to slide format and section size
Glass type	Soda lime, borosilicate	Borosilicate for UV and thermal stability
Mountant viscosity	Thin to thick, product dependent	Thicker media resist bubble formation
Set or cure time	Minutes to overnight	Leave slides flat until handled
Storage of medium	15 – 25 °C, tightly closed	Solvent mountants are flammable and volatile
Shelf life	12 – 24 months unopened	Discard media that has thickened or clouded

Choosing Between Aqueous and Resinous

The stain decides the medium. If the preparation must stay hydrated, as with immunofluorescence, enzyme reactions and a number of special stains, use an aqueous or non-setting medium and seal the rim. If the preparation has been through alcohol and a clearing agent, use a resinous medium so it hardens, matches the glass refractive index closely and can be handled, filed and re-examined for years.

The failure mode of resinous mounting is residual water: a section that is not fully dehydrated presents as a milky, cloudy slide, and no amount of extra medium will fix it. The failure mode of aqueous mounting is physical: an unsealed coverslip will move, dry at the edges and eventually lift. Both are avoided by finishing each step properly rather than by changing products.

Coverslipping Procedure

Mount in a fume hood or with local extraction when working with xylene-based media
Place one or two drops of medium on the section, enough to spread but not flood
Lower the coverslip from one edge so the medium advances ahead of the glass and pushes air out
Let the medium spread by capillary action; do not press down on the glass
Wipe surplus medium from the slide edges with a solvent-damp cloth before it sets
Lay slides flat in a drying rack to cure, then file them upright

Troubleshooting

Problem	Likely Cause	Fix
Air bubbles	Coverslip dropped flat, too little medium	Lower from one edge, use slightly more medium
Milky or cloudy	Residual water, incomplete clearing	Extend dehydration and clearing before mounting
Medium retracting from section	Trapped solvent evaporating after mounting	Cure flat, use fresh medium, avoid over-thin layers
Slides sticking together	Excess medium over the glass edge	Wipe edges before curing
Coverslip lifting	Unsealed aqueous medium	Rim seal with nail varnish or sealant
Fading fluorescence	Non anti-fade medium, light exposure	Use anti-fade medium, store slides dark and cold

Storage and Handling

Keep solvent mountants closed and away from ignition sources; they are volatile and flammable
Store coverslips in their original box, upright, to keep the glass clean
Handle coverslips with flat forceps or a vacuum pick-up tool, never fingers
File cured slides upright in labelled boxes, away from heat and direct light
Keep fluorescence slides in the dark at cool temperature to slow fading
Record batch number and mounting date for archival slides

Ordering Checklist

Stain type and whether the preparation stays hydrated
Required slide life: temporary working slide or long-term archival
Coverslip format, thickness grade and count per pack
Objective magnification and numerical aperture in use
Mountant refractive index and whether rim sealing is needed
Accessories: forceps, drying racks, slide boxes, blotting pads

Tell us the stain and how long the slide has to last, and we will match the coverslip grade, the medium and the sealing method as one package, with the accessories that keep the batch consistent.

Contact JWRESEARCH

JW RESEARCH SUPPLY — laboratory equipment and consumables, Singapore.
Telephone / WhatsApp: +65 8039 3660
Email: SINGAPORE@JWSHY.COM
Website: www.jwresearch.cn