The watch glass is one of the most versatile auxiliary labware items,
manufactured from neutral glass or borosilicate glass. Its concave
circular design allows it to fit snugly over beakers, evaporating dishes,
and other vessels — effectively preventing dust contamination and
reducing solvent evaporation. It also serves as a convenient platform
for holding micro-samples for observation and weighing. RichTech watch
glasses offer high clarity, excellent chemical stability, and a comprehensive
range of sizes — essential tools in chemical analysis, pharmaceutical,
and educational laboratories.
45 – 180 mmDiameter
1 – 2 mmApprox. Thickness
100 – 1000 pcs/casePackaging
Neutral GlassMaterial
Specifications are subject to confirmation with your enquiry.
* Dimensions are nominal values. Actual dimensions may vary slightly.
* Custom sizes and special specifications available upon request. Bulk pricing available.
* Borosilicate glass 3.3 watch glasses are suitable for heated applications (with appropriate equipment).
Size Selection Guide: Choose a watch glass 10–20mm larger than the vessel opening
for secure coverage and easy handling. Micro-sample applications → 45–70mm; Standard coverage → 90–120mm;
Large vessel coverage → 150–180mm.
Product Description
The watch glass is one of the most versatile auxiliary labware items,
manufactured from high-quality neutral glass or borosilicate glass.
Its distinctive concave circular design allows it to fit snugly over
beakers, evaporating dishes, and crystallizing dishes — effectively
preventing dust and contaminants from entering while reducing solvent
evaporation. The watch glass also serves as a convenient platform for
holding micro-samples such as powders, crystals, and precipitates for
observation, weighing, and microscopic examination. RichTech watch
glasses offer high clarity, excellent chemical stability, and a
comprehensive range of sizes — indispensable tools in chemical analysis,
pharmaceutical research, food testing, and educational laboratories.
Key Features
Premium Glass Material: Neutral glass or borosilicate glass 3.3 · Excellent chemical stability · Resistant to acids and alkalis
Concave Circular Design: Snug fit over vessel openings · Dust and evaporation protection · Micro-sample platform
High Clarity: High-purity glass enables clear observation of samples beneath
Smooth Surface: Precision-formed, smooth and flat — easy to clean
Chemically Resistant: Compatible with acids, alkalis, salt solutions, and common organic solvents
Comprehensive Range: Ten sizes from 45mm to 180mm — fits all common vessels
Value Proposition: Small but mighty — the watch glass delivers four essential functions
in one simple device: dust protection, evaporation prevention, sample holding, and observation.
One watch glass = Vessel cover + Sample stage + Viewing window — one of the most cost-effective and versatile labware items.
Quality Assurance
Each watch glass undergoes rigorous dimensional inspection, surface
flatness verification, and visual inspection. Our products meet
laboratory glassware quality standards.
Note: Watch glasses are concave-shaped — use with the concave side up as a cover,
or with the convex side up as a sample platform. Choose a watch glass with a diameter
slightly larger than the vessel opening. Inspect for cracks or chips before use.
Applications
Typical Application Areas
Vessel Covering
Cover beakers, evaporating dishes, and crystallizing dishes to prevent dust and contamination
Evaporation Reduction
Cover heating or standing solutions to reduce solvent loss and concentration changes
Micro-Sample Holding
Temporary platform for powders, crystals, precipitates, and other micro-samples
Weighing Aid
Alternative to weighing paper — hold solid samples for weighing
Evaporation Assistance
Place over evaporating dishes or water baths as a semi-permeable cover
Education
Covering demonstrations and sample presentations in chemistry courses
Watch Glass vs Petri Dish vs Crystallizing Dish
Watch Glass Concave circular — primarily for covering vessels and micro-sample holding
Petri Dish Flat-bottom shallow (lid + base) — primarily for microbial culture and cell culture
Crystallizing Dish Flat-bottom shallow (single piece) — primarily for crystallization and evaporation
Tip: The watch glass is one of the most fundamental auxiliary labware items.
For best results, pair with RichTech beakers, evaporating dishes, and crystallizing dishes.
Choose the appropriate size based on your vessel diameter requirements.
Watch Glass Operation Guide
03
Preparation Before Use
Inspect for cracks, chips, or edge damage
Wash with mild detergent and soft cloth/sponge — rinse 3 times with distilled water
Air dry or place in oven at 60°C
For aseptic applications, use dry-heat sterilization (160°C / 2 hours)
04
Covering Procedure
Select a watch glass with a diameter slightly larger than the vessel opening
Use clean tweezers or gloves to handle — avoid fingerprints
Gently place the watch glass over the vessel — the concave shape naturally aligns with the rim
When heating, do not seal completely — leave a small gap for gas escape
05
Sample Holding Procedure
Place the watch glass convex side up on a level surface
Carefully place micro-samples (powders, crystals, etc.) in the center of the concave surface
Observe directly under a stereomicroscope as needed
Place the watch glass directly on the balance pan for weighing
06
Cleaning & Maintenance
Clean immediately after use to prevent residue adhesion
Routine cleaning: Mild detergent + soft cloth/sponge — rinse 3 times with distilled water
Stubborn residues: Soak in dilute nitric acid or specialized cleaning solution
Air dry or place in oven at 60°C
When stacking, place soft paper between each watch glass to prevent scratching
Watch glasses are fragile — handle with care and avoid impacts
Care & Notes
Show care & notes
Safety Precautions
Inspect for cracks or scratches before use — damaged watch glasses may break when heated
Watch glasses are not suitable for direct heating (standard neutral glass is not heat-resistant)
Borosilicate watch glasses can withstand moderate heat but should not be exposed to open flames
Wear protective gloves and goggles when handling strong acids and alkalis
Do not
When covering heated vessels, do not seal completely — leave a gap to prevent pressure build-up
Avoid stacking too high during storage — bottom watch glasses may crack under pressure
