Custom Flat Mylar Bags

Finishes, Windows and Closures

Flat bags can be made in shiny foil, matt metallised film, white or kraft-look outer layers, all with a barrier layer inside. A matt finish gives a modern, premium look and reduces glare under shop lights. Gloss finishes make bright colours pop. Kraft-look film suits natural and artisan brands.

A clear window on the front shows the contents, which is useful for colourful teas, bath salts or granola. Just remember that a window lets light in, so it is best for products that are not light-sensitive or that sell quickly.

Closures depend on how the bag is used. A simple heat seal suits single-use sachets. Tear notches near the top let customers open the bag cleanly without scissors. A press-to-close zip turns a flat bag into a resealable pack for products used over several days. Hang holes, round or euro-slot, let bags hang on retail pegs. Shaped pouches cut to an outline rather than a rectangle are made as die-cut mylar bags.

Sizing Flat Mylar Bags

Size a flat bag by width and height, measured on the outside. Because there is no gusset, the usable volume depends on how full you fill it: a bag filled too full becomes pillow-shaped and is hard to seal neatly. Leave at least 20 mm of clear film above the contents for the heat seal, more if you add a zip.

The easiest test is to take a plain bag of a similar size, fill it with your product to the weight you plan to sell, and see how it looks and seals. Powders settle into a compact shape; leafy teas and crisp foods need much more room for the same weight.

For samples posted with orders, check the bag fits flat inside your mailer or envelope without bending. A bag that lies flat looks far neater on opening than one forced into a corner. Our guide to measuring products for packaging covers fill height for pouches too.

Printing and Artwork

We print flat mylar bags in full colour, front and back. Fine text, photographs and gradients reproduce well on film, and metallic film can be left unprinted in places to give a natural foil shine through your design.

Plan the layout around the seals. The top seal area and side seals are pressed flat during sealing, so avoid placing important text close to the edges. The back of a sachet is the natural home for ingredients, directions, allergens and your business details, while the front stays clean with the brand and product name.

If you sell several flavours or variants in the same size, a common design with a coloured band or a small label area for the flavour keeps the order simple. Upload the artwork through the free proof request and we will show the seal areas over it.

Sealing Your Bags

Mylar bags are sealed with a heat sealer, either a hand-operated impulse sealer for small batches or a band sealer for higher volumes. The inner layer of the film melts and bonds under heat and pressure, creating an airtight seal that is also tamper-evident: once opened, the bag cannot be sealed again in the same way.

Test your sealer settings on a few empty bags before filling. Too little heat leaves a weak seal; too much can wrinkle the film. Most small businesses find the right setting within a few tries.

If you are filling hundreds of sachets for an event or a subscription box, set up a small production line: one person weighs, one fills, one seals and one checks. Mark the fill line on a sample bag and keep it beside the scales so every sachet looks the same, and keep a few sealed bags from each batch to check later that the seals have held. Stand-up and gusseted formats for the full-size product sit under bags and pouches.

Fill a Plain Bag to Your Sale Weight First

Flat pouches have no gusset, so their real capacity depends on the product: 30 g of ground coffee sits flat in a 100 x 150 mm bag, while 30 g of loose-leaf tea needs the next size up. Take a plain bag close to the size you have in mind, fill it to the weight you will sell, and check it seals with at least 20 mm of clear film above the contents, more if a zip is added. Then pick closures: a tear notch, a zip for products used over days, a hang hole for pegs.

Send the size, finish, closures and quantity per design, and a custom quote comes back by email within one working day, with low minimums quoted per job. The free proof shows the bag outline, the seal areas and any window or hang hole. Production takes 4–7 working days after approval and tracked delivery to UK mainland addresses is free, taking 2–3 working days. Bags with faulty seals or print reported within 10 days are reprinted or refunded. Products that must be seen through the front move to mylar bags with a clear window in the same film.