Knowledge centre · Product properties
Viscosity and filling: how to measure product thickness and match the pump
Viscosity decides which pump can move your product at all. A little measurement discipline at the start saves the biggest problems at the end.
1. What viscosity actually tells you
Viscosity is resistance to flow — how thick a product is at a given temperature. It is the first property we ask about, because it decides the pump family: thin liquids (milk, beverages, edible oil) suit gear pump fillers; creams, gels and sauces suit rotor pump fillers; and thick pastes and fillings with particles sit firmly in the rotor pump range up to ≈300,000 cSt.
2. How to measure it
| Method | What you get | When it helps |
|---|---|---|
| Laboratory viscometer (Brookfield-type) | Viscosity in cSt or cP at a set temperature | The number your supplier needs for pump sizing |
| Rotational / spindle test | Viscosity curve across shear rates | Thixotropic or shear-thinning products |
| Simple flow cup (e.g. Ford cup) | Seconds to empty a calibrated cup | Quick plant-side comparison of batches |
If you do not have a viscometer, a practical shortcut is to describe the product honestly: "flows like honey", "like toothpaste", "holds a shape when scooped". This is enough for a first pump recommendation, and a filling test will confirm it.
3. Why temperature changes everything
Viscosity falls as temperature rises — sometimes dramatically. Hot-fill sauces can drop several viscosity classes between ambient and filling temperature. Always state viscosity at the actual filling temperature, not at storage temperature. If your process heats or cools the product before filling, say so in the equipment enquiry; it changes pump sizing, nozzle design and accuracy expectations.
4. Communicating viscosity to a supplier
- Give the number and the temperature: "120,000 cSt at 40 °C", not just "very thick".
- Note if it is shear-thinning: many sauces pump more easily at speed than they look at rest.
- Mention temperature range: cold start and hot fill may be two different products for the pump.
- Offer a sample: the most reliable step is a filling test with your actual product.