Quick answer
Prep a door for window tint by dropping the glass, cleaning the hidden top and side edges, both faces of the glass and the gasket felts, protecting the door card and switches with a towel, then scrubbing, flooding and card-passing the inside face. Inspect at a low angle against the light before any film comes out of the box.
Most contamination under film was on the door before the film arrived. This clip is the prep pass the Onyx team does on every door, and it is where the clean install is actually won.
Key takeaways
- Most contamination under film was on the door before the film arrived.
- Clean the edges hidden in the channel first: they carry the most grit.
- Towel the door card and tape the switch panel. Slip solution finds electronics.
- Five to eight minutes a door on a clean car. Never the place to save time.
Clean what the film will touch
Drop the glass and clean the top edge and the two side edges, which are the parts hidden in the channel most of the time and the parts that carry the most grit. Then clean both faces of the glass, then the gasket felts with a wrapped card and a towel until the towel comes up clean. The felt clean has its own post: cleaning contamination in gaskets.
Protect what you cannot clean
Tuck a towel along the door card and over the speaker grille. Slip solution finds electronics; the towel catches it. Tape any switch panel that sits below the glass.
Scrub, then flood, then look
A white scrub pad and solution across the inside face, a flood rinse, then a hard card pass to lift anything the pad loosened. Look across the glass at a low angle against the light. What you can see now will be under the film later.
The door prep checklist
- Drop the glass two to four inches.
- Clean the top edge and both side edges of the glass with a wet wrapped card.
- Run the inner felt and outer belt seal end to end until the towel comes up clean, then dry them.
- Towel the door card and speaker; tape the switch panel.
- Scrub the inside face with a white pad and solution.
- Flood rinse and hard-card the pane to lift loosened debris.
- Inspect at a low angle against the light. Repeat any step that shows specks.
- Raise and lower the glass once and check the top edge for a line of specks.
Old film and adhesive
A door that has had tint before needs the old adhesive off before anything else. Steam or a soak with solution softens it; a plastic razor lifts it. Steel blades score the glass and the channel and show up as scratches under a light shade. Old adhesive left in the channel comes back onto the glass with the first raise, so the felt clean comes after the adhesive removal, not before.
Prep pays twice with ceramic
On a dark dyed film a speck hides. On Onyx Ceramic, especially in 35% and lighter, the speck is visible from the driveway. The prep in this clip is the difference between a ceramic install that upsells itself and one that comes back. The same rule applies twice over on Ceramic+ 50%, which is why the Ceramic+ 50% walkthrough starts with prep.
Films mentioned in this post
Onyx Ceramic 35%
60% IR · 48% TSER · 99%+ UV
Where a clean prep shows. Signal-safe nano-ceramic, $410.
From $410 Shop →
Onyx Carbon 5%
73% IR · 56% TSER · 99%+ UV
The volume roll. Same prep, same comeback cost if skipped.
From $265 Shop →
Questions shops ask
How long should prep take?
Five to eight minutes a door for a clean car. Longer on a work truck. It is never the place to save time.
Do I need to remove the door card?
Rarely, for tint. Removing the inner weather strip clip is usually enough to reach the felt.
Which cleaner?
Slip solution and a scrub pad on the glass; never ammonia near the film, which we cover in the final-steps clip.
Do new cars need the same prep?
Yes. Factory glass often carries release agent in the channel and fibres from transport, and the felt has never been cleaned.
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.