Laboratory desiccators: how can samples be dried and stored away from moisture?

Indispensable for keeping moisture-sensitive reagents and samples dry, desiccators create a low-humidity microenvironment. Whether you need a vacuum desiccator to speed up drying, a desiccator cabinet for high-capacity storage, or a regenerable desiccant (silica gel, molecular sieve), controlling relative humidity safeguards weighings, analyses and storage. Robustness, airtightness and chemical compatibility guide the selection of a model suited to your routine in chemistry, quality control, environmental testing or the life sciences.

What are the different types of laboratory desiccators, and how do they work?

A standard desiccator is an airtight chamber (borosilicate glass or engineering plastic) where a desiccant (silica gel, molecular sieve, calcium sulphate, etc.) adsorbs moisture from the air. Samples sit on a perforated plate, kept separate from the desiccant to avoid contamination. Openings are controlled to limit moisture ingress and the desiccant is regenerated regularly.

The vacuum desiccator speeds drying by lowering the pressure via a vacuum stopcock and a high-integrity seal (ground joint with grease or an O-ring). Reduced pressure promotes cold evaporation and limits oxidation. It requires vacuum-rated materials, visual inspection of the walls, and good safety practice (protective screen, gradual evacuation/venting).

The desiccator cabinet offers a larger usable volume, with shelves and gasketed doors. In a passive, non-electrical setup, desiccant cartridges or trays maintain a low relative humidity. Ideal for bulk storage of dry glassware, filters, powders and hygroscopic reagents.

For desiccants, indicating silica gel is simple and safe (cobalt-free grades available), molecular sieves achieve very low humidity quickly, while calcium sulphate or calcium chloride are economical but messier. Regeneration is generally done in an oven (temperature depends on the material).

Selection criteria: volume and footprint, drying speed (passive vs vacuum), chemical compatibility (glass for aggressive solvents, polymers for light weight and impact resistance), closure and sealing type, presence of a hygrometer or indicator, ergonomics (trays, clamps), and safety requirements for vacuum use.

Type	Principle	Applications
Standard desiccator	Desiccant + airtight chamber	Dry storage of samples, filters, glassware
Vacuum desiccator	Pressure reduction + desiccant	Rapid drying of powders, sensitive preparations
Desiccator cabinet	Large volume + regenerable desiccant	Bulk storage of reagents and consumables

In which fields is a desiccator used?

• Life sciences: storage of lyophilised enzymes, dehydrated culture media, filters and disposables prior to culture.
• Pharmaceutical: drying of API powders, stabilising samples for relative humidity testing, storage of test tablets.
• Agri-food: sample preparation for moisture determination, filter drying, preservation of reference samples.
• Environmental: conditioning of filters/solids before gravimetric weighings, stability of reference standards.
• Chemistry & materials: drying of hygroscopic salts (NaOH, halides), polymers, gentle desiccation of adsorbents.
• Cosmetics: stability studies, storage of water-sensitive ingredients.
• Quality control: keeping samples dry prior to analytical weighing, Karl Fischer titrations, preparation of retention samples.

Available laboratory desiccator types

Frequently asked questions about laboratory desiccators

What is the difference between glass and plastic?
Glass offers better resistance to solvents and vacuum; plastics are lightweight and shock-resistant but more permeable and sometimes less chemically compatible.

How do I regenerate indicating silica gel?
Spread in a thin layer and heat as directed (typically 120–150 °C) until the dry colour returns. Allow to cool in a moisture-free area.

Is a vacuum desiccator faster?
Yes. Lower pressure accelerates cold evaporation and limits oxidation. Use only vacuum-rated models.

Can I store solvents?
Avoid bulk volatile liquids: they saturate the desiccant and may attack certain plastics. Prefer closed containers.

What is the alternative to cobalt indicators?
Use cobalt-free indicating gels (orange/green) to reduce risks linked to cobalt salts while keeping a clear readout.