How to use less packaging film without losing protection

How do you work out where the material savings are?

Start by weighing the polythene you use now, because film is bought and taxed by weight rather than by the micron. Weigh ten empty bags on scales that read to a tenth of a gram, average them, and you have grams of film per pack. Multiply by your annual volume and you have the number any change has to move.

Then work out the film area you are paying for. A flat polythene bag uses roughly twice its lay-flat width multiplied by its length, plus the sealed lip and any gusset. Set that against the footprint of the product going into it. A gap of 40 or 50mm on every side is easy to end up with, and it is film you are buying for no reason.

Finally, count your failures honestly. Splits, re-bags, damaged returns and packs that have to be double bagged all tell you where the current specification is already marginal. Those are the lines to leave alone, and the rest are where the saving lives.

What is downgauging and when does it actually save money?

Downgauging means specifying a thinner polythene film for the same job, for example moving a bag from 100 micron to 80 micron. Because film is sold by weight, a 20 per cent cut in thickness on the same bag size and the same polymer takes 20 per cent of the weight out, which is why downgauging is the first thing most people suggest.

Strength does not fall away neatly in step with it. Tensile strength tracks the cross section of the film reasonably closely, but puncture and impact resistance depend on how far the film can stretch before it tears, and that is governed by the polymer at least as much as the thickness. Two films at the same micron can behave completely differently under a sharp corner.

Downgauging works well where the film is over specified, where the product has no hard edges, and where the pack is handled in a controlled way. It works badly where the current film is already close to its limit. If your specification is quoted in gauge or mils, put it through our polythene thickness converter so you are comparing like with like.

Which polymer or blend lets you run a thinner film?

The polymer decides how much work each micron of polythene does. LDPE is soft, clear and easy to seal, and it is the default for general purpose bags. LLDPE stretches much further before it tears and resists puncture better at the same thickness, so an LLDPE rich blend will often hold a load at a lower gauge than straight LDPE. HDPE is stiffer and stronger in tension per micron, which is why very thin liners and counter bags are made from it, though it tears readily once a nick starts.

Blending is where most of the practical gain sits. We extrude film in house in Blackburn, so the blend is a variable we set against your load. Adding LLDPE or a metallocene grade buys toughness that you can then spend on a thinner gauge.

Co-extrusion goes further by putting different polymers in different layers of the same film, so a tough core does the structural work while the skins are tuned for sealing or slip. A film built that way often does at a lower total thickness what a single layer film needs more material to achieve.

How much film does right-sizing the bag save?

Right-sizing usually beats downgauging, because a bag takes material out of two dimensions at once. Trimming 25mm off the lay-flat width and 25mm off the length removes film from both dimensions of every unit, and the effect compounds across the run. Changing the gauge only ever moves one variable.

There is a second saving behind it. An oversized polythene bag lets the product move inside it, and a product that moves needs void fill, arrives creased, or needs a stiffer film to run on a bagging machine. Take the slack out and the film can often be lighter as well, because it is no longer being asked to bridge empty space.

Measure the product at its widest point, add its depth to work out the lay-flat width, then allow a working tolerance for the operator or machine. Our bag size finder will give you a starting point from your product dimensions. If the product is an awkward shape, a gusseted bag or layflat tubing cut to length wastes less film than a flat bag sized to the largest dimension.

When is thinner film a false economy?

Thinner polythene stops saving money the moment it starts failing. One split pallet cover, one refuse sack that bursts on the way to the skip, one mailing bag that arrives open, and the replacement goods or the carrier claim wipe out the film saved. Film is normally a small line on the cost of the delivered goods and an expensive thing to get wrong.

Watch the second order costs too. Film that is too thin can stretch and wander on an automatic bagger, seals less reliably because there is less material at the seal, and is harder for an operator to open and load. Downtime on a packing line is expensive in a way that a saving per kilo rarely covers.

Cold is the other trap. Polythene becomes less forgiving as temperature drops, so a specification that behaves perfectly in a warm factory in July can crack in an unheated yard in January. Sharp corners, dense heavy products, long routes with several handling points and outdoor storage are all reasons to leave the gauge alone and take the saving from the bag size or the blend instead.

How does recycled content fit into using less material?

Recycled content reduces the virgin polymer in a polythene pack without changing the pack at all, which makes it a different lever from thickness. We manufacture recycled options across much of our range, including refuse sacks made from post-consumer waste, and the recycled proportion is part of the specification we set with you.

It pulls against aggressive downgauging, and it is worth being straight about that. Reprocessed polymer is less consistent than virgin polymer, so at very thin gauges a high recycled content film can be less forgiving under an impact or a sharp corner than a virgin film at the same micron. In practice you pick a priority, either a lighter pack or one with more recycled material in it, and specify around it. Trials that chase both at once are the ones that fail.

There is a tax dimension as well. The UK Plastic Packaging Tax applies to plastic packaging that does not meet a minimum recycled content threshold, so a film that clears it is treated differently from one that does not. Rates, thresholds and registration duties change, so check the current figures on gov.uk rather than a number in an article.

How do you trial a lighter specification without risking a shipment?

Change one variable at a time. If you drop the gauge, switch the blend and shrink the bag in the same order, a failure tells you nothing about which change caused it. Run the new polythene specification alongside your existing one on the same products, line and route, and keep a sample of both.

Test it where it actually fails, which is rarely on a bench. Pack a real load, put it through your normal handling, send it on your longest route to your most awkward delivery point, and look at what comes back. If the product ships through winter, trial it in winter or chill the pack first.

We support one-off bespoke trials, so you do not have to commit to a year of stock to find out whether a lighter film holds up. Minimum order quantities vary by product and gauge, and bespoke runs are typically two to three weeks, quicker on repeat and standard specifications. Send us your current specification or a sample of the film you buy now, with the product weight and how it is handled, and we will tell you straight whether there is material to take out. Call 01254 691354 or email sales@morepolythene.co.uk.

Frequently asked questions

Will a thinner polythene bag always cost less?

Not always. Film is priced by weight, so a thinner bag does contain less material, but the saving disappears quickly if packs start splitting, need double bagging or slow a bagging line down. Compare the cost per thousand packs delivered intact rather than the cost per kilo of film.

How far can I downgauge before the film fails?

There is no universal figure, because it depends on the polymer, the product and how the pack is handled rather than on the micron alone. A film with a tough LLDPE or metallocene content can often drop a gauge step where a plain LDPE film cannot. The only reliable answer comes from running the lighter specification against your current one on real loads and a real route.

Does recycled polythene need to be thicker than virgin film?

Sometimes, yes. Reprocessed polymer is less consistent than virgin polymer, so at very thin gauges a high recycled content film can be less forgiving under an impact or a sharp corner. It is usually better to choose one priority, either a lighter gauge or a higher recycled proportion, and specify around it. Send us the load details and we will quote a recycled grade against the hold you actually need.

Is it better to change the bag size or the film thickness?

Bag size usually gives the bigger saving, because reducing the lay-flat width and the length takes film out of two dimensions at once while gauge only moves one. Right-sizing also removes the slack that lets a product move inside the pack, which often means the film has less work to do as well. Measure the product at its widest point, add its depth to work out the lay-flat width, then allow a working tolerance for handling.

How do I compare two quotes when the gauges are different?

Convert both to a cost per thousand bags rather than a cost per kilo, because a thinner film yields more bags from the same weight and a per kilo price hides that. Ask for the polymer blend as well as the micron, since two films at the same thickness can perform very differently under the same load. If one quote is for a different bag size, work back to grams of film per pack so the comparison is fair.