Stretch film: cast vs blown, pre-stretch, and how much a pallet needs

Two rolls of stretch film can look the same on a shelf, carry the same micron on the label, and still behave very differently on a pallet.

One may be cast and the other blown. One may be made for a machine that stretches it to three times its length, and the other for a person walking round the pallet.

If you want the answer before the details, here it is. For clean, square loads, start with cast film. It is clearer and quieter, and most stretch film sold is cast. For heavy loads with sharp edges, such as timber or paper reels, look at blown film, which resists puncture better. If you wrap pallets every day, a machine with powered pre-stretch will usually hold the load better and use less film than hand wrapping.

And whatever we choose, we should measure two things: film per pallet in grams, and containment force in kilograms.

Cast and blown: how each is made

We make blown film at Jagannath Polymers in Jaipur, so I know the blown process from our own floor. Molten polyethylene comes out of a ring-shaped die as a tube. Air is blown into the tube to make a tall bubble, which cools slowly as it rises. At the top, rollers flatten the bubble and the film is slit and wound.

Cast film is made differently. The melt comes out of a straight, flat die onto large chilled rollers, which cool it very quickly.

That difference in cooling is where the different properties come from.

Lantech, a stretch wrapping machine maker, estimates (updated April 2026) that 70 to 80% of stretch film made today is cast, and 20 to 30% is blown.

What the difference means on a pallet

The makers' own notes do not agree on everything, and I think you should know that before a salesman tells you otherwise. Lantech says blown film usually clings more, while Integrated Packaging, an Australian film maker, describes cast film (March 2021) as having excellent built-in cling. Lantech also says cast film resists tear propagation, while Sigma Stretch Film's brochure credits its blown film with tear resistance.

So I treat "cast or blown" as a starting point, not a verdict.

Formulation matters as much as process, and a good film of either type will beat a poor film of the other. My advice is to trial both on your own loads before you sign a yearly contract.

One more point about blown film. Lantech notes that the bubble is typically rotated as the film is blown and wound, which spreads out small thickness variations across the roll. That helps when films get thinner, because a small variation becomes a bigger share of a thin film.

Hand film and machine film

The material can be the same. The roll is not.

Poly-Pack, a German film maker, lists its range like this.

The European Commission's 2014 cargo securing guidelines give a wider picture: stretch wrap film is very thin, 10 to 30 micron, and mostly comes on 50 cm wide reels.

Hand film is often sold pre-stretched. It is stretched at the factory, so a person can put it on with little effort. That is useful, but the same EU guidelines warn about what it means for the load. A machine stretches the film twice, first between its rollers and then again between the rollers and the load. When the film is put on by hand, the second stretch is missing, and the guidelines say "there is almost no force between the load and the film". They recommend that pre-stretched film should not be used to rigidify loads by hand.

I will be honest about hand wrapping. Hand-wrapped film keeps cartons together and keeps dust off, but it does very little to stop layers sliding in a hard brake.

For heavy loads or long trips, a machine, straps, or both are the real answer.

Pre-stretch: where most of the savings are

Pre-stretch is the stretch a machine puts into the film before it reaches the load. It is given as a percentage of the original length.

1. 100% pre-stretch means 1 m of film becomes 2 m.
2. 200% means 1 m becomes 3 m.
3. 300% means 1 m becomes 4 m.

Lantech gives the example that 200% pre-stretch turns 6,000 feet of film into 18,000 feet. That is three times the coverage from the same kilograms we paid for.

For the setting itself, 3M's own pallet wrapping specification, RD-207 (revised December 2019), asks for 200 to 250%, because that range keeps film breaks low and film yield high. Some films are rated for more. Ask your supplier for the film's rated pre-stretch, and set the machine within it.

I would start any film trial with this check, because it costs nothing. We can check a machine in two minutes, using the method in that 3M specification. Draw two marks on the film exactly 10 cm apart before it enters the film carriage. Run the machine and measure the same two marks on the wrapped load.

• 20 cm apart means 100% pre-stretch.
• 30 cm apart means 200%.
• 35 cm apart means 250%.

The same 3M document says to check this at least twice a year. Damaged or worn stretch rollers and a broken drive chain are the usual reasons a machine quietly loses its pre-stretch.

Containment force: what actually holds the load

Containment force is the total squeeze of all the film layers on the load. Lantech puts it simply: containment force equals wrap force (how tight each layer goes on) multiplied by the number of layers.

This is why micron alone tells us little.

A thin film put on tight, in enough layers, can hold better than a thick film put on loose.

We need a containment force tool to measure it, and I would put one on the list before any new film trial. Lantech's guidance on checking containment force is practical.

1. Measure at the top, middle and bottom of the load, on the longest side.
2. Take the lowest of the three readings as your number. The load is only as safe as its weakest zone.
3. If your loads are shipping without damage, that number becomes your standard. If they are not, raise it.
4. Check at least once per shift.
5. Always use the same type of tool. Readings from different tools cannot be compared.

For a starting point, Lantech publishes guideline ranges for its own tool: about 1 to 2 kg for light, stable loads like tissue, 2 to 3 kg for short cases and cans, 3 to 5 kg for tall or heavy cases and bags, and 5 to 9 kg for bricks, blocks and bottled water. Lantech says these values are valid only with its own tool. Lantech also points out that no containment force tool is approved or certified by ASTM.

A wrap pattern that holds

The 3M specification gives a clear sequence. I have converted it to metric.

1. Attach the film to the pallet, and twist it into a rope that locks the film to the pallet about 2.5 to 5 cm below the top of the pallet. Any lower and forks can pierce it.
2. Spiral upwards, overlapping each layer by 40 to 60% of the film width.
3. Wrap 4 times round the top, with the film reaching 5 to 15 cm above the load.
4. Spiral back down with the same overlap.
5. Wrap 4 times round the bottom, covering 2.5 to 5 cm of the pallet.
6. Leave no film tail longer than about 10 cm. Lantech warns that long tails snag on equipment and can tear or unravel the wrap.

That rope at the base matters most, in my view. The film has to tie the load to the pallet, not just wrap the cartons to each other. If the load has corner boards, fit them before wrapping. Our guide to edge protectors and corner boards explains when they are worth it.

How much film does a pallet need? Measure it

No table can tell us this for our own load.

A weighing scale can.

Fromm, a packaging machine maker, describes a simple method.

1. Weigh a full roll, and weigh an empty core of the same kind.
2. Subtract to get the net film weight on the roll.
3. Wrap two or three pallets in your normal way.
4. Cut off the film and weigh it, then divide by the number of pallets.
5. Divide the net roll weight by the film per pallet to get pallets per roll.

We can also check that a roll holds the film we paid for. Stretch film resin is close to 0.92 g/cm³ (ExxonMobil's data sheet for one cast stretch film grade gives 0.917). So one metre of 500 mm film at 23 micron weighs about:

• 0.023 mm × 500 mm × 1,000 mm = 11,500 mm³ = 11.5 cm³
• 11.5 cm³ × 0.917 g/cm³ = about 10.5 g per metre

Divide the net film weight by 10.5 g and you have the roll length in metres, before stretching. If the label says more, ask why.

If I had to track only one number at a wrapping station, it would be grams of film per pallet. Once we know it, every change becomes a measured trial. Change one thing at a time: the film, the pre-stretch, the number of top wraps. Weigh again, measure containment force again, and keep the change only if both numbers and the delivered pallets say so.

Standards worth naming on a film data sheet

When we compare films on paper, we should ask which test method each number comes from. These are the current ASTM references.

Safety at the wrapping station

Hand wrapping is hard on backs. OSHA's grocery warehousing guidance describes the bending needed to reach the bottom of every pallet, and the cut fingers that come from gripping a roll by the open end of its tube. It recommends a turntable machine, and where people must still wrap by hand, the lightest rolls possible with a handle.

For machines, keep people out of the turntable's path while it runs, and never reach into the film carriage while the machine is live. The UK HSE lists BS EN 415-6 as the safety standard for pallet wrapping machines, so ask any machine seller whether their machine meets it.

If you send us your pallet size, load weight and how you wrap today through our contact page, we will suggest a film and a starting pattern to test. For loads going into a container, also read our guide to securing cargo in a container.