Experiment: The Basic Soak Test
What it demonstrates: The full-soak physics of Chapters 2.8–2.9 — and the real-world difference a glazing treatment makes to it.
Requirements: Two similar vehicles — one with film, one without (or the same model before and after installation, tested on comparable days). An infrared thermometer. A timer. Full sun.
Protocol:
- Park both vehicles simultaneously in identical full-sun exposure, oriented the same direction, windows closed, ventilation off.
- Allow a full soak — 90 to 120 minutes — letting both cabins approach their equilibrium plateau per Chapter 2.8.
- Measure both vehicles at the same moment: dashboard surface at a marked matching location, seat surface, inner glass surface, and cabin air at head height.
- Record all conditions: ambient temperature, time, sky, orientation.
The critical control is simultaneity. Sun angle and intensity change continuously; measuring both vehicles at the same moment removes the sun itself as a variable. Even a modest time offset on a partly cloudy day can swamp the effect being measured.
Reading the results. The surface measurements are the diagnostic ones — dashboard and inner glass reflect transmitted and absorbed energy most directly. The filmed vehicle should run measurably cooler at the surfaces, with the air gap typically smaller than the surface gap. The size of the difference is the experimenter's own data point: it varies with film construction, glass area, orientation, and climate, which is precisely why a personally measured figure under documented conditions outranks any generic claim. Small differences are findings too — film age, construction, and conditions all belong in the interpretation, and in the journal.
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