Perforation patterns: how much open area does your load need?

The question is asked in good faith and it has no catalogue answer. Open area is not something you pick off a shelf the way you pick a width. It is the output of a specification exercise that starts with the load. Two pallets of identical size and weight can need entirely different perforation, because one respires and the other is simply warm.

Toreto does not publish a perforation percentage for exactly that reason. Hole size and perforation count are engineered per load and confirmed at quotation. What follows is how to reason your way to the answer, so that the conversation with a packaging engineer starts from the facts that actually decide it.

Three separate demands hide behind the phrase “we need breathability”. The first is heat: goods that went into the wrap warmer than the air around them — hot-filled, cooked, freshly baked, straight off the line. They need bulk airflow through the stack until the temperature evens out, and they need it early.

The second is moisture: free water left after a wash-down, or vapour driven off when a cold pallet meets a warm dock. That is a smaller demand that runs for much longer, so the wrap has to stay open across the whole journey rather than move a lot of air at once.

The third is respiration. Living produce keeps generating heat, carbon dioxide and ethylene for as long as it is in the box, and that demand never stops. It is usually the one that decides the specification, because it is the only one still working while the pallet sits in a container halfway through a sea crossing.

If a supplier gives you a perforation figure, it describes the film flat on the roll — what was punched. What matters is the aperture that exists on the wrapped pallet, after the film has been power-stretched onto the load and has taken its final shape.

In our own team's field experience, that gap is where most perforated film on the market disappoints. It looks correct on the roll, but the base material will not stretch, so the holes barely open as the film goes on and the airflow never arrives. Aerosonic's holes open as the web is stretched, with the reinforcing strands between them intact. The useful question is what the wrap does on the pallet.

Hole size governs how much air moves through each aperture and what the wrap still keeps out. Larger holes shift more air and dry a load faster, and they have to be carried by reinforcement or the wrap loses containment where material was removed. Aerosonic Lite is the extreme of that approach: macro-perforated with large aeration holes and reinforcing bands, wrapping in a single layer where competing materials need several.

Hole count and distribution govern where the air actually goes. Many smaller apertures spread airflow evenly across the face of the load; fewer, larger ones concentrate it. A pallet with warm or damp spots in the middle of the stack has a distribution problem, and adding open area everywhere will not fix it.

Perforation gives air a way through the film. It does not give air a way through the load. If the cases inside are solid-walled corrugated, butted tight with no vent slots and no air channel up the middle of the stack, even a heavily perforated wrap can only ventilate the outer surface of the pallet.

Vented crates, slotted cases and a deliberate air channel in the pallet pattern are what turn perforation into cooling. Specify the stack first, then the film to match it. Getting that order wrong is how operations end up over-specifying the wrap to compensate for a load air cannot move through, and paying for open area that does nothing.

An engineer needs a short list of facts, and almost none of them are about film. What the product is and whether it is still respiring. What temperature it enters the wrap at, and what it passes through afterwards — cold store, dock, container, a summer sea crossing. How the pallet is built and whether the cases are vented. The weight, the height, and which wrapper you run at what power stretch.

From those facts, hole size and perforation count are set to the load, and the micron range is confirmed at quotation rather than taken from a published range. If the honest answer to your question is a number, it belongs on your quotation and not in an article.

Trialling it costs less than most buyers expect. Supersonic and Aerosonic are made from the same materials and perform the same, so a line can run a breathable trial at the same cost per pallet on unchanged machine settings, where other breathable films typically cost up to 100% more in use. In Toreto's own August 2026 wrap tests, both held 10 kg/sq in on 66 g of film a pallet.