Every polyester film starts as the same polymer, polyethylene terephthalate (PET), but it does not all look or behave the same. A carton window needs film you can see straight through. A label needs a bright white surface that makes print stand out. A drawing office needs a surface that takes pencil and ink, and a barrier pack needs film that keeps light and air out. The finish is what makes the difference.
This guide explains the main polyester film finishes, what each one does and where it is used, so you can choose the right one before you ask for a quotation. If you are comparing materials rather than finishes, start with our guide to polyester vs polypropylene film.
Finish, treatment and grade: what is the difference?
When people talk about a film's grade, they usually mean three things together:
- The finish: how the film looks and handles light. Clear, hazy, matt, white, black or metallised.
- The surface treatment or coating: how the surface behaves with inks, adhesives and machines. For example corona treated, chemically treated, slip or antistatic.
- The thickness: usually given in microns. Our polyester film thickness guide explains microns, gauge and mil.
This article is about the first of these. Most jobs need the right finish combined with the right treatment and thickness, and our guide to polyester film grades covers all three.
Polyester film finishes compared
The table summarises each finish. The thickness ranges are typical of grades from the major polyester film manufacturers; the exact thicknesses available vary from grade to grade.
| Finish | What it does with light | Typical uses | Typical thickness |
|---|---|---|---|
| Clear and crystal clear | Lets light straight through with very little haze | Carton windows, overlays, displays, laminates | 12 to 250 microns |
| Hazy (general purpose) | Transparent, with a slight haze from slip additives | Industrial uses, release liners, tapes, insulation | 9 to 350 microns |
| Matt and translucent | Scatters light on one or both sides | Drafting, backlit graphics, anti-glare overlays | 12 to 150 microns |
| Opaque white and milky white | Pigmented white, from fully opaque to softer, less opaque grades | Labels, cards, tags, printed graphics | 23 to 350 microns |
| Black | Pigmented and opaque, blocks light | Light blocking, insulation, decorative uses | Varies by grade |
| Metallised | Reflects light from a thin aluminium layer | Barrier packaging, decorative and reflective uses | 12 to 36 microns |
Clear and crystal-clear polyester film
Clear polyester is the film most people picture: glass-clear, stiff for its thickness and strong in thin gauges. Crystal-clear grades keep haze as low as possible, so the product or print behind them is seen sharply. That makes them the choice for carton and packaging windows, display overlays, protective covers and optical laminates.
Clear film is also the right choice when you print on the reverse side, so the print is seen through the film and protected by it. For packaging uses, see our guide to PET packaging and carton window film.
Hazy, or general-purpose, polyester film
Hazy film is still transparent, but it contains slip additives that make it easier to wind, unwind and handle on machines. Those additives scatter a little light, which gives the film its slight haze. Where nobody needs to look through the film, that does not matter, so general-purpose grades are widely used for tapes, release liners, industrial parts and electrical insulation. They also cover the widest thickness range.
Matt and translucent polyester film
A matt finish roughens the surface on one or both sides, so the film scatters light instead of letting it straight through. That does three useful jobs:
- It takes pencil and ink. Matt drafting film has long been used for technical drawings and plans, because it is far more stable and durable than tracing paper.
- It diffuses light. Backlit signs and displays use translucent film to spread the light evenly behind the graphic.
- It cuts glare. Matt overlays on control panels and displays are easier to read under bright lighting.
Our guide to polyester film for labels, graphics and print covers matt and drafting films in more detail.
White polyester film: opaque and milky
White polyester has pigment added during manufacture. Opaque white blocks light and gives a bright background for strong print contrast, which is why it is used for durable labels, barcodes, cards, tags and printed graphics. Milky white grades are less opaque, giving a softer white where full opacity is not needed.
White polyester resists tearing, water, abrasion and heat far better than paper, so it is chosen for labels and tags that have to survive outdoors, in workshops or through cleaning.
Black polyester film
Black film is pigmented right through, so it blocks light completely. It is used where light must be kept out, for example in electronics and light-sensitive products, as insulation where a black part is wanted, and for decorative and masking work.
Metallised polyester film
Metallised film has a very thin layer of aluminium deposited on it in a vacuum. The result looks like foil but keeps polyester's strength and flexibility. The metal layer reflects light and greatly improves the film's barrier to oxygen, moisture and light, which is why metallised PET is used in barrier and snack packaging, as well as for decorative and reflective uses.
One point to watch: the aluminium layer conducts electricity, so metallised film is not the choice where the film itself has to insulate. If your part needs to insulate, use an unmetallised grade.
Finishes and surface treatments together
A finish rarely works on its own. Most films are printed, laminated, coated or stuck to something, and that depends on the surface. Corona treatment raises the surface energy so inks and adhesives wet out and bond, and chemically treated grades carry a primer coat for demanding inks, coatings and adhesives. Slip and antistatic treatments help sheets feed and keep dust away.
So a label film might be opaque white and chemically treated, while a window film might be crystal clear and corona treated on one side. Tell us how the film will be printed or bonded, and we will match the treatment to the finish.
Five questions to choose the right finish
- Does anyone need to see through it? Choose clear or crystal clear. If not, a hazy grade may do the same job.
- Will it be printed on? White gives the strongest contrast. Clear works for reverse printing, and matt takes pencil and ink.
- Does light need to be spread, blocked or reflected? Matt or translucent spreads it, white and black block it, and metallised reflects it.
- Does it need a barrier? Metallised film adds a strong barrier to oxygen, moisture and light.
- Does it need to insulate electrically? Avoid metallised grades, and look at clear, hazy, white or black film instead.
Archival uses have rules of their own: conservators use clear polyester with no coatings, additives or plasticisers. Our guide to archival polyester film explains why.
From the right finish to the finished format
We supply clear, matt, white, metallised and treated polyester film, under our own Polymex® brand and from the leading film manufacturers. If your specification names a branded grade, give us its name or data sheet and we will supply it or recommend an equivalent. We then slit, sheet or cut the film to the reel width, sheet size or part your process needs.
Not sure which finish you need? Ask our technical team for a recommendation and a quote, with what the film has to do, how it will be printed or bonded, and the quantity, and we will come back to you with the right film for the job.
