Every film supplier has numbers. Very few have numbers you can compare. The difference is not honesty, it is method: a performance figure is only meaningful next to the glass it was measured on, the standard it was tested to, and the conditions the sample saw before the test.
Here is what to check, in the order that saves the most time.
1. The substrate is stated
A film does not have a VLT. A film on a particular glass has a VLT. The same construction on 6 mm clear float and on 6 mm body-tinted glass produces two different visible-light figures, because the glass absorbs before the film does anything.
If the report does not name the glass — type, thickness, coating — the number describes a laboratory stack that does not exist on your building. That is the first question to ask, and often the only one you need.
2. The standard is named, not implied
Solar-optical properties are calculated and measured to recognised methods: ASTM E903 and E892 for solar-optical properties and the SHGC calculation, EN 410 for the European equivalent, ISO 9050 for the international one. Safety film is a different family entirely — ANSI Z97.1, EN 12600, EN 356, ASTM F1642 — and each of those tests a different thing on a different rig.
"Tested to international standards" is not a standard. If the report does not carry a number and a date, treat the claim as marketing.
3. Conditioned, or straight off the roll?
Adhesive systems change with moisture and temperature. A sample tested immediately after coating and a sample conditioned for the period the standard requires can produce different adhesion and optical results. Reputable reports state the conditioning.
This matters most for exterior film, where the question is not what it does on day one but what it does after two summers. A weatherability claim without an accelerated ageing method attached is an opinion.
4. Measured value versus a range
A report gives a value with a tolerance. A brochure gives a range, and the range is usually the best result from the best run. When a supplier quotes "up to 99% IR rejection", ask which band, measured how, on what glass. The honest answer is specific; the marketing answer is not.
There is a second trap here. Infrared rejection is often reported at a single wavelength near 900–1,000 nm, which flatters more constructions than it describes. A film can show a very high figure at that point and a much lower average across the near-infrared band that actually carries the heat.
5. The batch, and the date
Film is coated, not printed. Two runs of the same construction can differ slightly, and a report from three years ago describes a formulation that may no longer be on the line. A report without a date and a batch reference is a historical document.
What you want, for a container order, is the batch record for the rolls you received — or at minimum a report from a run in the same formulation period, with the batch code traceable to your shipment.
What a usable report looks like
| Field | What it should say | What its absence means |
|---|---|---|
| Substrate | Glass type, thickness, coating | The number cannot be applied to your building |
| Standard | Number and edition, e.g. EN 410 | The claim is not comparable with anyone else's |
| Method | Measured or calculated, and by whom | You cannot tell a measurement from an estimate |
| Conditioning | Time and conditions before test | Adhesion and ageing claims are unverified |
| Traceability | Batch code and date | The report may describe a different product |
The uncomfortable part
Some of what buyers ask for does not exist. A supplier who says "this film makes the glass compliant with safety glazing requirements" is misusing a test that was performed on an assembly, not on a film. Film retains fragments; it does not convert annealed glass into a safety product. A report that appears to say otherwise is being read too generously — often by the person who wrote the brochure.
The same applies to blast and forced entry. Those are assembly tests: film, adhesive, frame, fixing and substrate, tested together and rated together. A film that passed on one frame does not pass on yours. Anyone who tells you otherwise has either not read the report or hopes you will not.
Which is the reason to ask for the document rather than the claim. What we can send is listed on the quality page, and if a project needs a specific standard we will tell you whether the report covers it before you order.
