What Is a Polythene Film Audit? How to Reduce Cost, Waste and Downtime

Packaging film is often bought against a specification that has remained unchanged for years. During that time, products, machines, line speeds, operators, sustainability targets and annual volumes may all have changed.

A polythene film audit checks whether the film being purchased still matches the way it is actually used. The purpose is not simply to find a cheaper price per kilogram. It is to identify the specification and supply arrangement that gives the most reliable cost per pack, reel or production hour.

What is a polythene film audit?

A polythene film audit is a structured review of film specification, reel format, machine performance, material waste, purchasing data and operational requirements. It can be applied to stretch banding film, collation shrink film, single-wound sheeting, lay-flat tubing, printed film, bags, sacks and liners.

A useful audit creates a measured baseline before recommending changes. That helps separate genuine film opportunities from assumptions and makes any trial easier to assess.

Why price per kilogram can hide the true packaging cost

Two films with the same price per kilogram can perform very differently. One may provide more usable metres per reel, run with fewer stoppages, seal across a wider operating window or create less start-up waste.

The more useful commercial measures are often cost per usable metre, cost per accepted pack and total annual operating cost. These measures can include film consumption, rejected packs, reel-change time, line interruptions and disposal of avoidable waste.

1. Record the current film specification accurately

The audit should begin with the specification that is actually being supplied, not only the description held in a purchasing system. Useful information includes:

• Film type, blend and intended application

• Width and measured thickness across several points

• Print, colour, treatment and additive requirements

• Core internal diameter, reel diameter, reel weight and winding direction

• Metres per reel where known

• Packing method, pallet format and label information

• Current order quantity, annual usage and delivery pattern

Reel labels, technical data sheets, retained samples and purchase records can help establish the baseline. Where information conflicts, physical measurement and a supplier specification review are important.

2. Observe the film on the actual packaging line

A film can look acceptable in isolation but behave differently once it is exposed to machine tension, sealing pressure, heat, dwell time and production speed. An audit should record what happens during normal running, start-up, changeovers and product variations.

Depending on the process, this may include tracking, seal consistency, film breaks, shrink response, blocking, slip, static behaviour, jaw contamination, pack presentation and the frequency of operator adjustment.

3. Measure waste instead of estimating it

Film waste is rarely limited to material placed in a waste bin. It can also appear as:

• Start-up film used before the line reaches stable settings

• Misfeeds, weak seals and rejected packs

• Excess overlap, oversized bags or unnecessary overhang

• Damaged reels and material left on cores

• Trial-and-error adjustments after reel changes

• Finished packs rejected later for appearance or containment problems

Recording waste by shift, product or reel batch makes it easier to identify whether the cause is the film, the machine setup, the pack design or a combination of factors.

4. Check gauge and consistency—not only nominal thickness

Nominal micron is only part of the picture. Thickness profile, consistency between reels, winding quality and material distribution can all affect how a film runs and how much material is used.

A proposed gauge reduction should be treated as a controlled technical change. The film still needs to meet sealing, puncture, shrink, containment and handling requirements. The safest opportunity is the lowest specification that performs consistently in the real application—not simply the thinnest film available.

5. Review reel format and operator handling

Reel format influences both machine compatibility and productivity. A larger reel may reduce changeovers, but only if the machine, shaft, guarding and operator-handling limits allow it. A lighter reel may be easier to handle but increase interruptions.

Core size, maximum reel diameter, reel weight, winding direction and splice expectations should be checked against the machine manual and actual operating practice. These details are particularly important for automated bagging, wrapping and banding equipment.

6. Separate film faults from machine-setting problems

Poor seals, film breaks or residue do not automatically prove that the material is defective. The same symptom can be caused by temperature, dwell time, pressure, tension, alignment, contamination or worn sealing components.

A good audit records the current settings and the condition of the contact surfaces before changing film. This prevents a new material from being used to mask an underlying machine issue—and prevents a sound film from being rejected because the line is outside its stable operating window.

7. Assess recycled content and Plastic Packaging Tax

Where performance and compliance allow, an audit can consider recycled-content film alongside virgin material and gauge optimisation. The comparison should include consistency, appearance, sealing, mechanical performance and supporting documentation—not recycled percentage alone.

For UK manufacturers and importers, HMRC states that plastic packaging containing less than 30% recycled plastic can be chargeable for Plastic Packaging Tax. The rate from 1 April 2026 is £228.82 per tonne. Packaging containing 30% or more recycled plastic is not chargeable, although it still counts towards the 10-tonne registration threshold and appropriate records are required. See the current HMRC Plastic Packaging Tax guidance for the latest position.

What should a polythene film audit produce?

The output should be practical enough to support a purchasing and production decision. Depending on the application, it may include:

• A documented baseline of film specification and usage

• A cost-per-metre or cost-per-pack comparison

• Identified causes of waste, downtime or inconsistent performance

• Recommended specification, reel or packing changes

• Samples and a controlled line-trial plan

• Commercial options that compare like with like

• An implementation and sign-off process for any approved change

Not every audit needs to recommend a new material. Sometimes the best result is confirming the current specification, correcting reel presentation, adjusting settings or improving supply planning.

When is the right time to review your packaging film?

• Repeated sealing, tracking, shrink or film-break problems

• A new machine, product format or packing-line speed

• A major increase in annual volume

• A supplier change or large difference between quotations

• Sustainability or recycled-content targets

• Frequent reel changes, excessive waste or inconsistent batches

• No documented film review for several years

What information should you prepare?

The review can begin with relatively simple evidence:

• Current film specification, reel label and technical data sheet

• A representative unused sample and, where useful, failed packs

• Machine manufacturer, model and operating settings

• Reel weight, metres per reel and annual usage

• Film purchase price and delivery pattern

• Waste, downtime and rejected-pack observations

• Product dimensions, weight and protection requirements

• Food-contact, print, treatment, recycled-content or traceability needs

From audit to controlled trial

Changes should be introduced in a way that makes the result measurable. Agree the success criteria before the trial, change as few variables as possible, record machine settings and compare the trial material with a known production reel.

This provides a clearer answer than relying on a short visual impression. It also creates an approval record for production, quality and purchasing teams.

How Stretchband Packaging can help

Stretchband Packaging offers a no-cost polythene film audit covering current specification, film usage, machine performance and opportunities to reduce avoidable cost or waste.

The review can include general polythene films, single-wound sheeting, collation shrink film and recycled and PCR options. If a change appears worthwhile, samples and a controlled trial can be agreed before any production commitment.

If you would like an independent starting point, send us a reel label, film sample and brief description of the application. Contact Stretchband Packaging for a practical review with no obligation to change supplier or specification.