Photoblocker Plate Sprays (Reflective Glare Tests)
Sprays marketed to make vehicle plates harder for cameras to read raise a different issue from lawful glare control, and I can’t provide instructions or tests for defeating plate imaging or enforcement. For building surfaces, use a documented glare review instead: measure gloss on a representative, non-vehicle sample, set project limits in advance, and check local requirements before installation.
New coatings and surface treatments can change how a building looks in sunlight, but a shiny finish is not automatically safe or suitable near a road, window, or sign. The result depends on the surface, the light source, and the viewing angle. A test from one direction cannot establish what people will see from another.
I focus here on lawful architectural glare evaluation. It can help you assess a façade or other building surface without testing vehicle plates or trying to interfere with cameras. The key is to separate a useful measurement from a claim it cannot prove.
Planning and Applicable Standards
This stage defines what is being assessed and which rules may apply. For a building coating, ASTM D523 provides a method for measuring specular gloss, while CIE 150 offers guidance on limiting obtrusive light from outdoor lighting. Neither standard sets a universal coating pass level or proves that a surface is safe in every setting.
What the standards can and cannot establish
ASTM D523 measures specular gloss, or how strongly a surface reflects light in a mirror-like direction. Its listed measurement geometries are 20°, 60°, and 85°. These are instrument angles, not pass/fail thresholds. Choose a geometry that suits the material and purpose, and record it with each reading.
CIE 150 concerns the limitation of obtrusive light from outdoor lighting installations. It can inform a broader review of light impacts, but it is not a coating-approval test. Check the current editions of both standards before using them, and confirm how they apply to your project.
A gloss value alone does not show whether a coating complies with local law, works safely at all sun angles, or suits a particular camera. Building-code provisions depend on the site and assembly. The IRC and IBC do not provide general approval for glare-producing coatings. Ask the authority having jurisdiction (AHJ), the body responsible for local approvals, which rules apply.
Set project criteria before testing
Define the purpose of the review before taking measurements. Identify the building surface, its location, nearby roads and windows, and the likely viewing directions. Then document a project-specific acceptance range and who will approve it. There is no general ASTM D523 limit supplied here, so do not adopt an invented universal number.
Keep separate records for measured gloss and visual or site-based glare review. A gloss reading describes a property under a set instrument geometry; it does not predict every real-world reflection. If a contractor, product sheet, or report claims that one number proves safety or legal compliance, ask what evidence supports that claim.
Key takeaway: Confirm the applicable standard editions and local requirements first. Agree on the decision criteria before testing, not after seeing the results.
Site Survey and Viewing Clearances
A site survey maps the surface and the people or places that could be affected by reflected light. Record the coating location, nearby roads and windows, and plausible viewing directions. This step helps identify risks that a single lab measurement cannot cover, including a reflection that shifts as the sun or viewpoint changes.
Map the surface and viewpoints
Record the surface type, its orientation, and the area proposed for coating. Note nearby public rights-of-way, neighboring properties, windows, signs, and locations where people may look toward the surface. Use a site plan or annotated photographs where available. The goal is a clear record of what was considered, not a claim that every possible viewing angle has been tested.
Consider changing conditions, including the sun’s position and the direction of travel or view. A surface that looks subdued from one spot may produce a concentrated reflection from another. This is an important edge case: one-angle gloss data cannot establish performance through all times of day, seasons, or approach directions.
Identify approvals and review needs
Before applying a coating near a public road or neighboring property, ask the AHJ about applicable building, lighting, façade, roadway, or sign rules. Requirements vary by location and project. A building owner’s approval does not replace any required public or local review.
If the surface is near a road, include the relevant road authority when local rules or site conditions call for it. If glare could affect a neighboring property, involve the property owner or project team in the review. Document who was consulted and what approval is still pending.
Key takeaway: Make a written list of locations, viewpoints, and approvals. Do not treat a successful sample reading as permission to install.
Sample Preparation and Measurement
This step uses a representative, non-vehicle sample to assess a proposed architectural coating. Record the sample, surface condition, instrument, and ASTM D523 geometry. Follow the product and instrument instructions, and keep the test away from vehicle plates and public-road vehicles. A sample result is useful only when its limits are clear.
Prepare a representative sample
Use a sample that reflects the intended architectural surface and coating system. Record the substrate, coating product, preparation method, and condition of the sample. Follow the coating maker’s instructions for sample preparation and curing. Do not assume that a sample on a different material will behave the same way as the planned installation.
Keep the sample clearly labeled and separate from vehicles and vehicle plates. This review is for building materials only. It is not a method for assessing, choosing, or applying any product intended to hide, confuse, or defeat plate imaging.
Record instrument and geometry
Use a gloss meter suitable for the sample and follow its operating instructions. Record the instrument make and model, calibration or verification status if available, measurement geometry, and surface condition. Take readings in a consistent way and note the locations measured. A reader should be able to understand how the result was obtained and what it represents.
ASTM D523’s 20°, 60°, and 85° values refer to measurement geometry. They are not limits for approving a coating. Select and document the geometry before testing, and do not compare readings taken under different geometries as if they were the same measurement.
Key takeaway: Keep a traceable record for each sample and reading. If sample preparation or measurement conditions change, record the change rather than blending the results.
Results, Acceptance, and Verification
Results should be compared with written, project-specific criteria and reviewed alongside the site conditions. A gloss reading is not a stand-alone safety test, and it does not establish legal compliance or camera compatibility. Record uncertainty and unresolved questions, then obtain needed approval before installation.
Compare results with the agreed criteria
Use the table below as a record template. It contains no universal pass values: fill in the criteria agreed for the project before measuring. If a result falls outside those criteria, pause and ask the project lead or qualified reviewer how to proceed. Do not change the acceptance range after seeing the result just to make it pass.
| Record item | What to document | Why it matters |
|---|---|---|
| Sample | Substrate, coating, and condition | Shows what material was tested |
| Measurement | Instrument and ASTM D523 geometry | Makes the reading traceable |
| Result | Reading and measurement location | Supports comparison with criteria |
| Criteria | Project-specific range set in advance | Defines the decision rule |
| Site review | Viewpoints and nearby roads or windows | Captures factors a meter reading misses |
| Approval | Reviewer, AHJ, or authority response | Records whether installation may proceed |
Do not treat a favorable reading as proof of safe performance from every viewpoint. A coating may reduce visible glare in one direction yet create a concentrated reflection at another. When the site review identifies a concern, seek a qualified lighting or façade professional’s assessment and follow the relevant authority’s direction.
Illustrative project scenarios
The following are examples of how to organize a review, not reports of completed projects or claims about actual test results.
- Road-facing façade: A project team proposes a coating on a wall near a public road. It maps likely viewpoints, checks with the relevant authority, tests a representative sample, and waits for review before installation.
- Building beside windows: A team notes that nearby windows may receive reflections at certain angles. It records those locations for the glare review rather than relying on one gloss reading.
- Unclear acceptance range: A supplier provides a gloss reading but no project criteria. The team documents the gap and agrees on a review process before treating the result as acceptable.
These scenarios show why a result needs context. A number without a defined geometry, sample description, and acceptance rule cannot carry the whole decision.
Key takeaway: Compare results only with criteria agreed in advance. Obtain required approvals before installing near public or neighboring spaces.
Conclusion
A responsible glare review starts with scope: architectural coating only, no vehicle plates or plate-imaging tests. ASTM D523 can describe gloss at specified geometries; CIE 150 can inform review of obtrusive light. Neither supplies a universal coating limit or proves legal compliance. Survey the site, test a representative sample, document results, and ask the local authority what approval is needed.
Key takeaway: Treat measurement as one part of a site-specific decision, not as a guarantee.
Frequently Asked Questions
These answers distinguish what a gloss measurement can show from what it cannot. They also outline the safe scope of the guidance: evaluating architectural surfaces, not testing products on vehicles or plates.
Can a gloss reading prove that an architectural coating is safe?
No. It records gloss under a stated geometry and test setup. It does not show performance from every viewpoint or prove legal compliance.
What angles does ASTM D523 use?
ASTM D523 includes measurement geometries of 20°, 60°, and 85°. These are measurement settings, not acceptance limits.
Is there a universal pass value for building coatings?
No universal pass value is provided here. Set project-specific criteria before testing, and confirm them with the relevant reviewer or authority.
Does CIE 150 certify a coating?
No. CIE 150 provides guidance on limiting obtrusive light from outdoor lighting installations. It is not a coating certification or approval test.
Can one measurement cover different viewing angles?
No. A measurement at one geometry cannot establish what a viewer will see from other directions or as the sun moves.
Should a sample be tested on a vehicle or plate?
No. This guidance is limited to representative, non-vehicle architectural samples. It does not cover testing treatments on vehicles or plates.
Who decides whether a coating may be installed?
The applicable authority depends on the project and location. Ask the AHJ and any relevant road or local authority before installation near public or neighboring spaces.
What should a test record include?
Record the sample and its condition, instrument, ASTM D523 geometry, reading locations and results, agreed criteria, site-review notes, and approvals.
(This article was written by one of our staff writers, Steven Langford. Visit our Meet the Team page.)
