Quick answer
Dry-shrinking is heat-forming window film on the outside of a back glass before it goes inside the car. The film is anchored in an H pattern, the excess is gathered into a few fingers, and a moving heat gun shrinks each finger flat. Done right, one pattern fits the glass with no cuts or relief slits.
Back glass is where new installers lose the most film. This clip shows the dry-shrink: laying the film on the outside of the glass, anchoring it, and using heat to pull the excess into a flat panel before it ever sees the inside of the car.
Key takeaways
- Anchor an H pattern first: one horizontal line across the middle, one vertical line down the centre.
- Gather twenty small fingers into three or four large ones before you heat anything.
- Keep the gun moving and let the card follow the heat, never lead it.
- Ceramic film holds heat: drop the gun a notch and slow down compared with dyed film.
- Work the lower band, then the sides, then return to the corners last.
Set the anchor lines first
Dust the outside of the glass lightly with baby powder or a dry-erase pass so the film slides, lay the film liner-out, and squeegee an H pattern: a horizontal anchor across the middle and a vertical anchor down the centre. Everything outside the H is where the fingers will form. Keep the anchors firm; a soft anchor lets the film creep and you chase it all afternoon.
Read the fingers before you heat
Fingers point to where the excess film wants to go. Gather them into a few larger ones rather than heating twenty small ones. Heat from the anchor outward with the gun moving, never parked, and let the card follow the heat, not lead it. Push the shrunk material toward the edge and away from the anchor.
The shrink, step by step
- Clean the outside of the glass and dust it lightly so the film can slide.
- Lay the rough-cut pattern liner-out with at least an inch of margin on every edge.
- Squeegee the horizontal anchor across the middle, then the vertical anchor down the centre.
- Gather the fingers above and below the anchor into three or four large ones with a dry card.
- Heat each finger from the anchor outward with the gun moving, then flatten it with the card following the heat.
- Work the lower band, then the sides, then finish the corners with the film already mostly flat.
- Let the panel cool on the glass, then trim to the final edge and move it inside.
Curve-by-curve, not corner-by-corner
The most common burn happens in the lower corners when the installer tries to finish the corner in one shot. Work the lower band first, then the sides, then return to the corners with the film already mostly flat. Small, repeated passes beat one aggressive one.
Gun settings and distance
Most installers run a variable gun between 350 and 450 °C (roughly 650 to 850 °F) for dyed and carbon film and one notch lower for ceramic. Keep the nozzle three to four inches off the film and moving at a walking pace. If the film goes glossy or the finger snaps flat with a crack, the gun is too close or too hot; back off before the next finger. A defroster grid on the glass is a useful gauge: if the lines shimmer through the film, the heat is right.
Why ceramic shrinks differently
Nano-ceramic film shrinks more predictably than dyed film because the ceramic layer holds tension evenly, but it also holds heat: the same gun setting that flattens a dyed panel will overshoot a ceramic one. Drop the heat a notch and slow down. Onyx Ceramic+ (96% infrared rejection and 71% total solar energy rejected at 5% VLT) is the film shops reach for on the back glass of premium installs, and it rewards patience. Onyx Ceramic shrinks the same way at a lower roll price.
Wide glass and roll width
A 40" roll covers the back glass on almost every sedan and coupe in one piece. Large SUVs, crew-cab trucks and minivans regularly need the 60" roll, which we stock in Lodi in Carbon and Ceramic. A 60" roll cut 36/24 gives you a back-glass strip and a door strip from the same roll, which is the cheapest way to stock for mixed work. Where the roll lives between jobs matters too; see why accessible tools are essential.
Films mentioned in this post
Onyx Ceramic+ 5%
96% IR · 71% TSER · 99%+ UV
96% IR rejection. The premium back-glass roll. $700 a 40" roll.
From $700 Shop →
Onyx Ceramic 20%
68% IR · 53% TSER · 99%+ UV
Same predictable shrink, $410 a 40" roll, 60" available.
From $410 Shop →
Questions shops ask
Wet shrink or dry shrink?
Dry is faster once learned and leaves no water to manage on the outside of the glass. Wet is more forgiving for beginners. Most production shops end up dry-shrinking back glass.
How do I stop the film sliding on the anchor?
Less powder, firmer anchor strokes, and let the glass cool if the sun has been on it. A hot pane makes every anchor soft.
What roll width for back glass?
40" covers most sedans and coupes; large SUV and truck rear glass often wants the 60" roll, which ships from our California warehouse.
Why does my film burn in the corners?
The corner is being finished in one shot with the film still loose. Flatten the lower band and sides first so the corner only has a small finger left, then heat that finger in short passes.
Onyx Distribution supplies wholesale window film to professional tint shops across the United States from warehouses in Lodi, California and Jarrell, Texas. Pickup in Lodi Monday to Friday, 9am to 4pm. Questions: support@onyxautomobilia.com.