Printing variable data, barcodes, and date codes onto mylar and other PET films with a TIJ 2.5 (HP45-format) printer comes down to one thing: ink chemistry. Mylar is a non-porous polyester film, so the ink cannot soak in the way it does on paper or corrugated. Adhesion and dry time have to come from a solvent-based ink formulated for non-porous media. Use the wrong ink and the code beads up, smears, or rubs off. This guide explains the difference between mylar and PET, why solvent ink is required, and which Kao Collins inks Ink4Mail recommends for polyester film.
Mylar vs. PET — What Is the Difference?
PET (polyethylene terephthalate) is the polymer — the raw plastic chemistry. It appears in three very different forms: polyester fiber, rigid PET (bottles and thermoformed trays), and PET film. Mylar is a brand name for a specific type of PET film: BoPET, or biaxially-oriented PET, stretched in two directions to make it thin, strong, and dimensionally stable. Like “Kleenex” for tissue, “mylar” is widely used as a generic term for almost any polyester film. In short: all mylar is PET, but not all PET is mylar. A spec sheet that lists “PET” confirms the chemistry family, but not whether the material is a film or how its surface is treated — and on non-porous film, that surface treatment is what determines whether the ink holds.
Why You Need a Solvent Ink for Mylar
Mylar is non-porous, so water-based and aqueous inks have nowhere to absorb — they sit on the surface, dry slowly, and smear. Solvent-based TIJ inks are formulated for exactly this situation: the solvent carrier evaporates quickly and leaves the pigment or dye bonded to the film surface, producing a fast-drying, smudge-resistant, scannable code. For mylar, PET film, foils, and similar non-porous packaging materials, a solvent ink is the correct class — not the aqueous coated-stock inks used for paper and chipboard.
Surface Treatment Determines Adhesion
Two rolls of mylar with the same “PET” spec can behave completely differently under a print head, because adhesion depends on how the film surface is finished:
- Corona-treated or chemically primed (topcoated) mylar — raised surface energy, so solvent inks adhere well.
- Untreated mylar — low surface energy, where ink can bead or rub off even when the chemistry is right.
- Metallized (aluminized) mylar — the shiny silver film used in pouches and balloons behaves differently again.
This is why no ink manufacturer certifies a product for “mylar” by name. They specify the polymer family (PET, PP, PE, foils) and rely on a substrate evaluation for the specific film. Before committing to a large order, the safest path is to confirm the ink against a sample of your actual film and treatment.
Recommended Inks for Mylar / PET Film
Kao Collins SIGMA+ — Highest Adhesion on PET and Metallized Film
For PET film, our lead recommendation is SIGMA+ (TSK3646), Kao Collins’ next-generation HP 45si solvent black. Kao Collins describes it as formulated for the highest level of durability and adhesion with extremely fast drying, and rates its decap at over 16 hours. The Sigma family is listed by Kao Collins for nylon BOPP, PE, PET, PP, foils, aluminum and laminated papers, and is EuPIA, REACH SVHC, Non-CMR and PFAS-free compliant for non-contact surfaces of consumer packaging. Shelf life is 12 months, so order to consumption rather than stockpiling. SIGMA+ is a drop-ship item shipped by UPS ground — see current pricing and order in the shop.
Kao Collins SIGMA — Longest Decap for Intermittent Lines
SIGMA (TSK3182) shares the same solvent chemistry and substrate range, with a longer decap time (over 64 hours, per Kao Collins) and a 24-month shelf life. Choose it over SIGMA+ when the line idles between prints or sits over weekends and nozzle readiness matters more than the last increment of dry speed. SIGMA is also a drop-ship item shipped by UPS ground — see current pricing and order in the shop.
Collins Stratus (TSK281503) — Solvent Ink for Difficult Films
The Collins Stratus (TSK281503) is a solvent-based ink formulated for difficult media including plastic wrap, PVC, Tyvek, foils, UV coats, varnish, and some metals, with a fast dry time. It is a strong solvent option for non-porous films and foils. Note that Kao Collins lists Stratus for plastic wrap and foils rather than naming PET specifically, so for PET film we recommend confirming suitability for your film with us before ordering.
A note on shipping: Because they are solvent-based, SIGMA+, SIGMA and Stratus ship as specialty, drop-ship items — by UPS ground only, directly from the manufacturer, not as same-day or air dispatch from our warehouse. Contact us to confirm current lead time before ordering.
Confirm Your Film Before You Order
Because adhesion on polyester film depends on treatment, a few details let us match the right ink the first time. When you reach out, tell us:
- Is the mylar corona / chemically treated, or untreated?
- Is it clear or metallized (aluminized)?
- Film thickness (mil or gauge), and the printer model you are running.
- Your throughput and any cure/handling steps after printing.
With those details we can recommend SIGMA+, SIGMA or Stratus, advise on an adhesion test, and confirm the specification directly with Kao Collins for your exact film.
Get a Mylar Ink Recommendation
Need to print on mylar or PET film and want to be sure of the ink before you commit? Email info@ink4mail.com or call 866-465-2278 with your film and printer details, and we will recommend the right solvent ink and confirm it for your substrate. Browse the full TIJ 2.5 ink catalog.