Direct answer
Foil is a barrier decision
A silver pouch can be foil, metallized film, or a printed effect. Those are not the same barrier, the same stiffness, or the same print job. Choose the layer because the product needs oxygen, moisture, or light protection, not because a render looked metallic.
If the product is stable in a clear structure, a foil layer is extra specification, not a default. Send the product and the shelf life you need before anyone locks the word mylar into the RFQ.
What buyers mean by mylar
Polyester film, often called PET, is a common outer web. Metallized film is a polymer film with a very thin metal layer. Foil is a metal web in its own right. Buyers say mylar for all three, and sometimes for a clear barrier film that is neither foil nor metallized.
In the RFQ, retire the nickname. Write PET, metallized PET, foil laminate, or unknown, and attach a sample. The stand-up guide covers the pouch shape. This page covers the layer.
When the extra barrier is doing work
Oxygen-sensitive, moisture-sensitive, and light-sensitive products are the usual reason. Coffee, oily snacks, and products that lose aroma are common examples. The product, the fill, and the shelf life decide it. A window in the pouch gives up some of that light barrier on purpose. Say if you need a window.
Ask for barrier data with units and test conditions if you have a number you must hit. A sample of the current structure is the right starting point when you do not have the number. WVTR and OTR pages explain why the test conditions matter.
What changes in the spec
Foil and metallized structures add layers, and they change how the pouch feels, folds, and shows print. Opaqueness is part of the light barrier. A clear polyester outer web can still carry reverse print over a metallized or foil layer behind it.
Do not describe the job as a silver pouch and stop. Name the layers or send the sample, and say whether a window, a valve, or a zipper is required. Those features interact with the structure.
Printing on foil and metallized film
Reverse print on a clear outer web is the usual way to protect ink in a laminate. Surface print leaves ink on the outside and may need a coating. White ink is often part of the build when the art sits over a dark or metallic layer. Count it.
PCI prints on two Uteco 10 color presses. Send the file or a color count. The press does not choose foil versus metallized. The product does.
A simple use-case table
Use the table as a question list, not as a structure you can order by row. Your product can be the exception. Say so in the RFQ.
How to specify so quotes match
Write one of these, and attach a sample if you have one: clear barrier, metallized, or foil laminate. Add the pouch style, the size, the features, the color count, the quantity, and the shelf life you need. Ask each supplier to restate the structure in the quote.
If a quote says mylar and another says metallized PET, they may or may not be the same film. Make them use the same words before you compare.
Ask for a structure recommendation
Tell Matt the product and the shelf life you need. Get a structure recommendation before you specify a foil layer you may not need.
| Product situation | Question to ask | Do not assume |
|---|---|---|
| Needs light blocked | Foil, metallized, or an opaque structure? | That silver ink is a barrier |
| Needs aroma held | Which layer is doing that job? | That any laminate is enough |
| Must show the product | Where is the window, and what barrier is left? | That a window keeps full light barrier |
| Current pouch works | What is the structure on the spec? | That a photo names the layers |
| Art over a dark layer | Is white ink in the color count? | That the file already includes it |
Questions buyers ask
Is mylar the same as foil?
Not necessarily. Buyers use mylar for polyester film, metallized film, and foil laminates. In the spec, name the structure or send a sample.
Does my product need a foil barrier?
Only if the product, the fill, and the shelf life need the oxygen, moisture, or light barrier a foil layer provides. Send those facts before you specify foil.
Can a foil pouch include a clear window?
A window is a designed clear area. It changes the light barrier. Say that you need one, and where it sits, so the structure and the art match.
How does printing work on metallized film?
Often as reverse print on a clear outer web, with the metallized layer behind it. White may be one of the inks. Count it. Send the file or a color count.
What structures are common for coffee and snacks?
Barrier structures, often metallized or foil when aroma, oxygen, moisture, or light matters. The right one is the one that matches your product and shelf life, confirmed against a sample or a spec, not a category habit.
See something that needs correcting? Tell Matt.