Foam persistence
A dense foam band may sit above the true liquid surface and change differently across products or batches.
Fill-level inspection ›
Foam-aware bottling inspection
Foaming & Carbonated Liquid Fill Inspection UK
Automated fill-level checks engineered to distinguish acceptable product behaviour from true underfill and overfill on moving bottling lines.
Direct answer
How do you inspect fill level when the product foams?
Create a repeatable inspection condition, then measure the feature that best represents the true fill—not simply the highest visible bubble.
This may mean allowing settling distance after the filler, stabilising the container, controlling illumination, analysing both liquid and foam bands, or selecting high-frequency, X-ray or weight-based sensing when ordinary vision cannot separate them reliably.
Why false rejects happen
Foam and liquid movement change after filling.
The product condition at the inspection point must stay within the range used during testing. Changes in speed, temperature, recipe, pressure and conveyor disturbance can alter the visible boundary.
Slosh and turbulence
Transfers, curves, belt gaps and unstable guides can tilt or oscillate the fill boundary during image capture.
Container optics
Condensation, coloured glass, moulding marks, labels and changing wall thickness can hide the useful signal.
Feasibility brief
Test the worst normal product condition.
Samples should represent the full operating range rather than only clear, settled product from a laboratory bench.
- Product formulation, carbonation, viscosity, temperature and foam behaviour
- Time and conveyor distance between filling, capping and inspection
- Bottle or jar material, colour, wall features, labels and condensation
- Line speed, pack pitch, curves, transfers, vibration and guide condition
- Acceptable foam or bubble variation versus genuine low and high fills
- Recipes, changeover checks, consecutive-failure alarms and reject response
Technology routes
Use the pack and product to choose the method.
No single sensing method is best for every foaming liquid. The useful distinction is whether the real fill can be observed or inferred consistently at production speed.
Vision and controlled lighting
Suitable where a repeatable liquid or foam boundary remains visible through the container.
High-frequency or X-ray
Assessed where foam, decoration or opaque packaging makes the optical boundary unreliable.
Checkweighing
Uses pack mass when quantity control matters more than the physical height of the moving liquid.
Practical answers
Questions about foaming products.
Final tolerances are confirmed using real samples, production speeds and the expected range of product behaviour.
Ask an engineerCan machine vision ignore foam above the liquid?
Sometimes. The image may allow liquid and foam boundaries to be treated separately, but performance depends on contrast, bubble structure, container optics and how consistently the product behaves at the inspection point.
Should inspection be moved further from the filler?
Extra settling distance can help, but it must be balanced against available line space and reject location. Testing identifies whether distance materially improves separation between good and failed fills.
Can the same recipe inspect still and carbonated variants?
Usually each product and pack combination needs its own validated recipe because the boundary, foam behaviour and acceptance region may differ. Recipe selection can be linked to line changeover controls.
What causes changing false-reject rates?
Common causes include product temperature, carbonation, filler behaviour, wet or dirty containers, ambient light, conveyor disturbance, wrong recipes and changes in bottle or label material.
Talk to Oxford Vision Systems
Send us product video from the real line.
Compare the age of the fill at the inspection point
Foam behaviour changes with elapsed time after filling. Two lines with the same distance between filler and camera can present different product conditions if they run at different speeds. Record the time from filling to inspection during normal production, along with any accumulation or stops, instead of relying on conveyor distance alone.
As an initial planning calculation, travel time equals distance divided by conveyor speed when movement is continuous and the product follows the belt. Use consistent units and treat the result as an estimate; curves, transfers and queues can change the actual journey. Review a production video to identify the condition seen by the sensor at the fastest and slowest intended operation.
Also include the first containers after a line stop. They may have had longer to settle than the products that follow them, which can change the apparent boundary without a change in quantity. A representative trial should distinguish that acceptable behaviour from true underfill or overfill. Send a short sequence showing steady running, a normal pause and restart so the inspection-point review reflects the real bottling process.
Why is filler-to-camera distance insufficient for a foaming product?
The elapsed settling time also depends on conveyor speed, accumulation and stops.
Should restart bottles be included in a fill-level trial?
Yes. Containers held during a pause may have a different foam condition from those inspected during steady running.
Prepare a fill-level inspection brief Review fill trends alongside process conditions