Laboratory viscometers: how can the flow behaviour of a fluid be characterised?

From paint to syrup, viscosity governs flow, adhesion and stability. Viscometers characterise Newtonian and non-Newtonian liquids, optimise formulations and secure reproducible quality control. From the ultra-precise glass capillary to the rotational electronic viscometer for shear profiles, via the flow cup and the consistometer, you measure at the right shear rate and at the right temperature, with full traceability and compliance with standards. Temperature-control accessories and spindle sets complete the offer, covering anything from a few mPa·s to hundreds of Pa·s.

What are the different types of viscometer and how do you choose the right one?

Four families cover most requirements. The electronic rotational viscometer measures the torque of a spindle (cylinder, cone-plate, helical) immersed in the sample: ideal for non-Newtonian fluids, speed ramps, shear profiles and R&D monitoring (ref. ISO 3219). The capillary glass viscometer (Ostwald, Ubbelohde) determines kinematic viscosity from flow time at controlled temperature, the metrological reference for Newtonian liquids (e.g. ASTM D445 / ISO 3104). The viscosity cup (Ford, Zahn, ISO 2431) offers a quick shop-floor check for paints and inks. The consistometer (Bostwick type) evaluates pourability and texture of sauces, purées or gels.

Key selection criteria: measuring range (mPa·s to Pa·s), fluid type (Newtonian / non-Newtonian), temperature control (thermostatic bath, Peltier cell), accuracy/repeatability, sample volume, chemical compatibility and standards compliance. Also consider cleaning (solvents, aqueous rinse), mechanical robustness (glass vs stainless steel), traceability (data output, LIMS) and accessories (low-viscosity adapter, small-volume kits, vane spindles for filled products).

Type	Principle	Applications
Rotational (electronic)	Torque under controlled shear	Creams, gels, inks, adhesives, R&D
Glass capillary	Flow time at fixed temperature	Oils, solvents, fuels (reference)
Viscosity cup	Efflux time through orifice	Paints, varnishes, shop-floor control
Consistometer	Flow distance/texture	Sauces, purées, food

In which fields is a viscometer used?

• Food & beverage: texture adjustment of sauces, syrups and fermented milks; batch-to-batch consistency and storage stability.
• Cosmetics: control of the sensory feel of creams, gels and shampoos; management of stringiness and spreadability.
• Pharmaceutical: syrups, ointments and suspensions; pharmacopoeia compliance and process robustness.
• Chemicals/paint/inks: application suitability (brush, spray), anti-drip/anti-sag performance, thixotropic rheology.
• Petrochemicals & lubricants: kinematic viscosity of oils, viscosity index, ASTM/ISO compliance.
• Environment: characterisation of sludges and leachates for treatment process control.
• Materials R&D: polymers, resins, additives; structure–property correlation and processing/forming.

The different types of viscometers available

Frequently asked questions about laboratory viscometers

Rotational or capillary: how to choose?
Capillary for Newtonian liquids and reference measurements (ASTM D445/ISO 3104). Rotational for non-Newtonian, shear profiles, speed ramps and R&D monitoring.

Does temperature affect the measurement?
Yes, markedly: a 1 °C change can skew the result. Use a thermostatic bath or a Peltier cell and always state the temperature (e.g. 20, 25 or 40 °C).

How do I set the shear rate with a rotational instrument?
It depends on the geometry (cone-plate, cylinder). The correlations are supplied by the manufacturer and described in ISO 3219. Select the speed to cover the region of interest.

What maintenance does a viscometer need?
Clean immediately, dry carefully, check spindles/capillaries, and calibrate periodically (ISO/17025 certificate). Store glassware safely away from knocks.

Can you measure filled products (particles)?
Yes, with rotational systems, using vane/helical spindles and suitable cups/beakers. Avoid capillaries and cups if particles may block the orifice or disturb the flow.

What are viscosity cups for?
Rapid production checks on paints/varnishes. They provide an efflux time correlated with viscosity, but accuracy depends on the temperature and the standard (e.g. ISO 2431).

What sample volume should you plan for?
Rotational: from 7–10 mL (low volume) up to 500 mL depending on geometry. Capillary: typically 5–15 mL. Cup: 50–100 mL. Consistometer: around 75 mL depending on the model.