Install technique

How to heat-shrink window tint for curved glass.

Your tint is flat. Your back window is not. Glass on most cars curves in two directions at once — side to side and top to bottom. That's a compound curve, and flat film can't lie on one without something giving. Force it and you get wrinkles that never come out.

The part nobody tells you first

You shrink the film on the outside of the glass, with the backing still on, before it ever goes inside the car. Not inside. Not after it's stuck down. Outside first, every time. If you've seen a video of someone waving a heat gun around inside a car, they were touching up a small bubble — that isn't shrinking.

Why outside?

1. Same shape, both sides. The outside of the glass has the same curve and dimensions as the inside. Form the film to the outside and it fits the inside.
2. The liner is still on. The backing protects the adhesive, so you can slide, heat and handle the piece as much as you need without contaminating the sticky side.
3. You have room to work. Shrinking inside means crouching over the back seat, working upside down, with a heat gun near your headliner. Outside, you stand up straight and see the whole piece.

The shrinking step is where the shape gets locked in. The inside step is just sticking it down.

What you need

A heat gun. A hair dryer is too weak to shrink film — you need a real heat gun.
A hard card — a stiff plastic squeegee card.
Slip solution — 1 L distilled water with 3–4 drops of unscented baby shampoo.
A few microfibre towels.
Your precut tint piece, cut for that exact window.

The step-by-step process

Step 1
Clean and wet the outside of the glass
Clean the outside of the window. It doesn't have to be surgical — this side never touches the adhesive — but get the grit off so you're not dragging dirt under the film. Then soak the glass with slip solution (1 L distilled water + 3–4 drops of unscented baby shampoo). Generously. The film needs to float and slide, not grab.
Step 2
Lay the film on the outside, liner facing you
Set the precut piece on the wet outside glass with the clear liner still on and facing up toward you. You are not peeling anything yet — the backing stays on for the whole shrinking process. Line the edges up with the glass, then look for the loose humps where the film lifts off the curve. Those are fingers, and they're what you're about to shrink away.
Step 3
Anchor the middle
Squeegee a stripe straight down the centre of the piece, top to bottom, with your hard card. This pushes the water out and locks the middle of the film to the glass. Do this before any heat — unanchored film slides under the heat gun and you end up shrinking the wrong area. Once the centre is set, every finger sits out at the edges where you can work them one at a time.
Step 4
Shrink the fingers, one at a time
Hold the heat gun 4–6 inches from the film and sweep it steadily across a single finger — never park it in one spot. Within a few seconds the film relaxes and drops toward the glass, almost like it's deflating. The instant it lays down, chase it with the hard card, pressing from the anchored centre outward. Then move to the next finger. Work top to bottom, one side at a time; jumping around pops up the areas you already did.
Step 5
Check your work
Run a flat hand across the whole piece. It should sit against the glass everywhere — no lift, no ripples, no loose edges. Any finger still standing gets another pass of heat and another card-down; doing it a few times is fine. When the whole piece lies flat on the outside with the liner still on, the shaping is done and it will stay that way.
Step 6
Now go inside and apply it
Clean the inside glass thoroughly, then clean it again — anything left behind gets sealed under the film permanently. Soak the inside glass with slip solution. Carry the shrunk piece in, peel the liner while spraying the adhesive so it never touches itself or dries out, and lay the piece on the wet glass. Because it's already shaped, it drops into the curve. Squeegee centre-out in firm overlapping strokes and mop the runoff with a microfibre towel.

Because the shape was already set outside, the interior step should feel almost easy. That's the whole point of shrinking first.

Do side windows need shrinking?

Usually no. Front and rear door glass is close to flat, and a precut piece will lie down with just slip solution and a squeegee. The pieces that almost always need shrinking are the back glass — the most curved piece on the car and the hardest — rear quarter windows on many SUVs and coupes, and some steeply raked sedan back windows. Lay a piece on the outside; if you see no fingers, skip the heat and go straight inside.

Mistakes that cost you a piece

Peeling the liner before shrinking

Now you have exposed adhesive out in the open collecting dust, sticking to itself, and about to get hit with a heat gun. This ruins pieces. The liner stays on until you're inside the car.

Heating film that's already applied inside

By then the adhesive has grabbed. Heat won't reshape it — it'll haze or lift it. Once the piece is inside, heat is only for tiny finishing touches on a small bubble.

Holding the gun too close or too long

Overheated film goes hazy, crinkles, or takes a hard permanent wrinkle. Keep it 4–6 inches away and keep it moving. If the film looks like it's changing colour, you've gone too far.

Not anchoring the centre first

The film slides under heat, you shrink the wrong section, and the piece is now distorted and won't fit the window it was cut for.

Rushing the interior cleaning

Every speck you leave behind is visible forever. No amount of squeegee pressure removes a hair once it's under the adhesive.

What's actually happening to the film

Window tint is polyester. When you heat it, the material contracts — it pulls in on itself and gets slightly smaller in the area you heated. That contraction is what removes a finger. You're not stretching the film over the curve; you're shrinking the excess out of it so a flat piece becomes a curved piece.

That's also why it's permanent. Once the film has shrunk it holds that shape and won't spring back as it cools — exactly why you do it before applying and not after.

Practise before you touch the back glass

Back glass is the hardest piece on the car. Don't make it your first. Work in this order:

1. The practice piece

Most install kits include one. Get a feel for how fast the film reacts to the gun and how hard to press with the card.

2. Front door windows

Nearly flat and very forgiving. Usually no heat needed at all beyond setting the edges.

3. Rear doors and quarter glass

A little curve, small pieces. This is where shrinking starts to matter, but the pieces are small enough to recover from.

4. Back glass, last

The hardest piece on the car. By the time you get here, shrinking should feel routine instead of terrifying.

When to stop and use the guarantee

If a piece has a hard crease, has gone hazy from overheating, or has picked up debris under the adhesive — stop. That piece is finished, and trying to save it just wastes the rest of your afternoon.

Install the pieces you can, and let the guarantee cover the one that fought back.

The short version

1. Wet the outside of the glass.
2. Lay the film on it, liner still on, facing you.
3. Anchor the centre with your card.
4. Heat each finger from 4–6 inches away and card it down as it drops.
5. Confirm the whole piece lies flat.
6. Then clean the inside, peel the liner, and apply.

Shape it outside. Stick it inside. That order is the entire skill.

Heat-shrinking FAQ

Do you heat shrink window tint on the inside or the outside of the glass?

Outside, always, with the liner still on. The outside of the glass has the same curve as the inside, the backing protects the adhesive while you work, and you can stand up straight instead of crouching over the back seat. Once the piece lies flat on the outside, you clean the inside glass, peel the liner and apply it there.

Can I use a hair dryer to heat shrink window tint?

Not for shrinking. A hair dryer doesn't get hot enough to contract polyester film — it will warm it without pulling the fingers out. Use a real heat gun for shrinking. A hair dryer is only useful for gentle finishing work.

What are fingers in window tint?

Fingers are the loose humps of excess film that stand off the glass when a flat piece is laid on a curved window. Heat contracts the film and removes that excess, so the finger drops onto the glass and stays there.

How far away should the heat gun be when shrinking tint?

About 4–6 inches, moving in a steady sweep across one finger at a time. Never hold it still. If the film starts changing colour or hazing, you're too close or you've lingered too long.

Which windows actually need heat shrinking?

Back glass almost always, rear quarter windows on many SUVs and coupes, and some steeply raked sedan back windows. Front and rear door glass is close to flat and usually goes on with slip solution and a squeegee. If you lay a piece on the outside and see no fingers, skip the heat.

Why is heat shrinking permanent?

Heating polyester makes it contract — the material pulls in on itself and the heated area gets slightly smaller. You're not stretching film over a curve, you're removing the excess from it. Once shrunk, the film holds that shape and won't spring back as it cools, which is exactly why you do it before applying.

Precut for your exact glass

Every piece is computer-cut for your year, make, model and body style — shrinking is only about making it sit in the shape it's already cut for. Free shipping over $99, ships from Canada.

Find my vehicle Full install guide Cleaning glass before tinting