When window tint turns purple, the film is dyed film and the dye is breaking down in sunlight. Bubbling usually means the adhesive under the film is failing. Both problems come from cheap film, and neither can be fixed once it starts. This page explains why it happens, how to tell what kind of film you’re being sold, and what to do about tint that has already failed.
Why tint turns purple
Dyed window film gets its colour from a mix of dyes soaked into a polyester base. The mix usually includes red, blue and yellow dyes, which together look neutral grey or charcoal.
Sunlight carries UV energy, and UV breaks down dye molecules over time. The dyes don’t all break down at the same speed. Yellow dye goes first. Once the yellow is gone, the red and blue are left, and red and blue together look purple.
This isn’t one bad batch of film. Every dyed film is open to it. Better dyed films include UV stabilizers that slow the fading down. The cheapest films leave those additives out or use too little of them, so they look fine when they’re new and start to fade much sooner.
Carbon, ceramic and multilayer films don’t rely on dye for their colour, so they don’t fade this way. That’s why the three 3M films we install don’t turn purple.
Why tint bubbles and peels
All automotive window film is held to the glass by a layer of adhesive. On quality film, that adhesive is made to stay clear and flexible for years in sun and cold.
Cheap film uses weaker adhesive. Heat and UV break it down, and as it breaks down it gives off gas. The gas collects between the film and the glass and forms bubbles. These bubbles don’t go away. They spread as more of the adhesive fails, and the only fix is to remove the film.
Bubbles that are normal
Small water pockets right after installation are different. They’re leftover moisture from the install, and they clear up on their own as the film dries. That can take a few days in warm weather and a few weeks in a Calgary winter. Our tint care guide explains what to expect.
Bubbles caused by the install
Good film can still bubble if it’s installed badly. Common causes are dirty glass, too little squeegee pressure that leaves water trapped, and film that wasn’t shaped properly to curved glass.
Calgary’s temperature swings
Calgary’s cold winters, hot parked cars in summer and quick chinook swings make the adhesive expand and contract over and over. Good adhesive handles it. Cheap adhesive goes brittle in the cold and soft in the heat, and it starts to separate from the glass.
How the film types compare
| Dyed | Metallized | Carbon | Ceramic | |
|---|---|---|---|---|
| How it works | Dye absorbs light | Metal reflects light | Carbon particles absorb infrared | Ceramic particles absorb infrared |
| Turns purple | Yes | Rarely | No | No |
| Signal interference | No | Yes | No | No |
| Heat rejection | Low | Moderate | Moderate | High |
For more on each type, read our guide to tint types.
How to avoid getting cheap film
All new tint looks the same on the day it goes on. The difference shows up a year or two later. Some sellers take advantage of that. They advertise a known brand at a very low price, then install generic film or a cheaper line. Here’s how to protect yourself.
- Ask for the exact product. “We use 3M” isn’t enough, because every brand makes several lines. Ask for the product line and the shade, such as 3M Ceramic IR in a particular shade.
- Ask to see the box and the roll. Genuine film comes in branded packaging with the product name on it. If the film comes off an unmarked roll, be careful.
- Check the dealer list. 3M, XPEL, LLumar and other brands list their authorized installers on their own websites. If a shop claims a brand, look it up there.
- Find out who backs the warranty. A manufacturer warranty is registered with the film maker. A warranty that only comes from the shop is worth nothing if the shop disappears.
- Be wary of prices far below everyone else. Quality film costs real money. A full-vehicle “ceramic” job priced far below established shops is a sign the film isn’t what’s advertised.
- Look for a real shop. Clean tint work needs a clean, enclosed space and good lighting. Film installed in a parking lot picks up dust.
- Look at it closely when it’s new. Quality film looks clear apart from the normal drying haze. Film that looks milky, wavy or has a brown or reddish cast on day one is a bad sign.
We’re a 3M Certified Pro Dealer, and we install three 3M films: Colour Stable, Ceramic IR and Crystalline. Ask us which one is going on your vehicle and we’ll tell you.
What to do if your tint has already failed
Purple or bubbled film can’t be repaired. It has to come off, and the old adhesive has to be cleaned off the glass before new film can go on. We can remove the old film and install new 3M film in the same visit. Our tint removal guide explains the process if you’d rather try it yourself.
If you’re replacing failed film, step up to carbon or ceramic so it doesn’t happen again. 3M Colour Stable starts at $299 and 3M Ceramic IR starts at $349.
Ready to replace purple tint? Send us a quote request.