Laboratory Dewar flasks: how can products be handled and stored at cryogenic temperatures?

From snap-freezing to holding a reactor at very low temperature, they stabilise your sensitive protocols by limiting evaporative losses. Available in steel, stainless steel or HDPE, they meet the needs of the laboratory and quality control, with capacities, neck diameters and accessories to match. The static evaporation rate (SER) becomes predictable, and safety is enhanced by vented, non-airtight lids and ergonomic handles.

What types of Dewar flasks are there, and how do you choose the right one?

A Dewar is a double-walled vessel with the interspace evacuated to eliminate conduction and convection. A reflective finish minimises radiative heat transfer. The narrow neck, non-sealed lids and internal geometry reduce LN2 boil-off and stabilise temperature.

• Steel Dewar: rugged and cost-effective, handles knocks and heavy use well. Heavier and potentially prone to corrosion if unprotected. Ideal for in-house handling, cold traps and cryo baths.
• Stainless-steel Dewar: 304/316 stainless for superior cleanliness and corrosion resistance.
• HDPE Dewar: double-walled plastic with insulating foam. Lightweight, unbreakable and safe for teaching or one-off manipulations (LN2, CO?). Higher SER (Static Evaporation Rate) than a vacuum-insulated Dewar; best for short durations.

Selection criteria: usable capacity (1 to 50 L+), neck diameter (racks, tongs, canes), SER (Static Evaporation Rate) and hold time, weight and ergonomics (handles, castors), compatibility with LN2/ CO?, cleaning requirements (polished stainless), and safety (neck guard, splash cover). Environmental impact is gauged via durability (reusable stainless, recyclable HDPE) and by reducing cryogen losses.

In which fields is a Dewar flask used?

• Life sciences : cell cryopreservation, snap-freezing of samples, maintenance of cryogenic storage dewars, and cryo-forceps for biopsies.
• Pharmaceuticals & biotechnology : LN2 transfers between vessels, cold stability testing, handling sensitive formulations.
• Chemistry & synthesis : cryosynthesis, -78 °C bath (CO?/acetone), cold traps for vacuum pumps and evaporation.
• Food & beverage : cryogenic milling, extraction of thermosensitive flavours, quality control analyses.
• Environment : preconcentration and capture of volatiles (GC/MS) using cooled traps, sample preservation.
• Cosmetics : handling thermosensitive ingredients, accelerated cold stability tests.
• Quality control & metrology : temperature reference standards, controlled thermal shock testing.

The different types of Dewar flasks available

Frequently asked questions about Dewar flasks

What’s the difference between steel, stainless-steel and HDPE Dewars?
Steel is rugged and cost-effective; stainless steel prioritises cleanliness and corrosion resistance, while HDPE is lightweight and shatterproof but less insulating—ideal for short-duration use.

How do I size my Dewar flask?
Balance usable volume, SER, desired hold time, neck diameter (racks, tongs) and filled weight. Allow some margin to minimise refills and time with the neck held open.

Can a Dewar be sealed airtight?
No. A Dewar must remain vented to release gas. A non-sealed lid limits splashes while preventing dangerous overpressure.

Are HDPE Dewars suitable for LN2?
Yes, for LN2-rated labware models and for short durations. Check the manufacturer’s temperature rating and avoid long-term storage.

What safety precautions should I take?
Wear cryogenic gloves, a face shield and a lab coat; work in a well-ventilated area; avoid low-lying or poorly ventilated spaces; and never decant at face height. Never seal the vessel.

Can LN2 be transported in a Dewar?
Only in Dewars designed for transport, with neck protection and anti-tip/anti-spill features. Follow internal procedures and safety signage.