Quick answer: Containment force is how firmly stretch wrap squeezes a load together. It comes from the film trying to shrink back after it’s been stretched, added up across every layer on the pallet. It depends on four things: how much the film was stretched as it went on, how thick it is, how many layers there are, and how even the tension was. More layers or more stretch gives more force. Too little and the load can shift. Too much can crush cartons or tear the film.
People often judge a wrapped pallet by how much film is on it. What actually holds the load is containment force. Here’s what it is, what controls it, and how to check it without special equipment.
What containment force is
When stretch film is pulled longer as it goes on, it tries to pull back to its original length. Wrapped round a pallet, it can’t, so it presses inwards on the load instead. That inward pressure is containment force. It’s what stops cartons sliding, stops the top layer shifting, and keeps the load square when a lorry brakes or turns.
It’s different from tensile strength, which is how hard you can pull film before it breaks. Our guide on tensile strength explains that side of it.
What controls it
Stretch
Film that’s stretched more as it goes on pulls back harder. Film put on slack, at full width, gives almost no containment force however many turns you use. Our guide to what “up to 500% stretch” means covers how much stretch you realistically get by hand.
Number of layers
Each layer adds its own pull. Roughly speaking, twice as many layers gives about twice the force. That’s why the base and top of a pallet, where you add extra turns, are held hardest.
Thickness
Thicker film can be stretched harder before it tears, so each layer can hold more. That’s the main reason 23 micron suits heavy loads better than 17 micron. Our 17 vs 23 micron guide explains when each makes sense.
Even tension
If the tension drops halfway up the pallet, that band of the load is held less firmly. Loads tend to fail at their weakest band, not their strongest. A hand dispenser with a brake helps keep tension even. See do you need a hand dispenser?
How much is enough?
There’s no single right figure, because it depends on the load. Heavy, tall or unstable loads need more. Light, square, stable loads need less. Sites that wrap by machine sometimes measure containment force with a gauge that pulls the film away from the load at set points, and set a target for each type of pallet. When wrapping by hand, most businesses judge it by feel and by how loads arrive.
How to check it by hand
- Press the film firmly on each side of the load, top, middle and bottom. It should feel tight and spring back, with no loose bands.
- Check the film catches the pallet at the base all the way round.
- Watch the load as a forklift lifts and sets it down. Nothing should lean or move.
- Ask customers and drivers about loads that arrive leaning or damaged. That’s your best real-world test.
Our printable pallet load security checklist puts these checks on one page.
Too much force
More isn’t always better. Very high containment force on light or soft cartons can crush corners and bow the sides of boxes. Pulling film too hard also makes it thinner, so it tears more easily on sharp edges. If boxes arrive dented at the corners, or the film keeps tearing, ease off the tension and use edge boards on the corners. Our guide on why pallet wrap keeps tearing has more fixes.
Getting more force without more film
- Stretch the film properly as it goes on instead of adding extra slack turns.
- Add turns where they matter, at the base and top, rather than all the way up.
- Keep the tension even with a dispenser if you wrap a lot of pallets.
- Match the film thickness to the load.
Our guide to cutting pallet wrap costs safely goes into more detail.
FAQs
What is load containment force?
The inward pressure stretch wrap puts on a pallet load, created by the film trying to shrink back after being stretched.
Does more wrap mean more containment force?
Only if it’s stretched as it goes on. Loose, unstretched turns add plastic but very little force.
Can containment force be too high?
Yes. It can crush light cartons and makes the film more likely to tear on sharp corners.
Which film gives more containment force?
At the same stretch and number of layers, thicker film holds more firmly. For heavy loads, 23 micron is the usual choice.
Related guides: how stretch wrap keeps loads safe in transit, stretch film for heavy pallets, pallet stability testing (EUMOS 40509).