Haze is the scattering of transmitted light that makes a nominally transparent material look cloudy or milky. It can reduce see-through quality even when a sample still transmits a large amount of light. That is why haze, color and total transmittance should be treated as separate results.
What haze means
When light passes through a clear specimen, much of it continues close to its original direction. Particles, phase boundaries, surface texture, scratches and internal structure can redirect part of that light. A defined haze method quantifies the wider-angle transmitted scattering relative to the transmitted light collected by the instrument.
Haze is not the same as transmittance or clarity
| Property | Practical question |
|---|---|
| Total transmittance | How much visible light passes through the specimen in total? |
| Haze | How much transmitted light is scattered beyond the method’s angular boundary? |
| Clarity | How sharply can fine detail be seen through the material, often influenced by narrow-angle scatter? |
| Transmission color | What color does the transmitted light have under the stated calculation conditions? |
A film can therefore have high total transmittance and still show objectionable haze. Two samples can also have similar haze but different transmitted color.
Control the specimen and method
ASTM D1003 defines haze as the percentage of transmitted light scattered more than 2.5° from the incident beam; narrow-angle scatter below 2.5° is associated with clarity. Procedure A uses a hazemeter, while Procedure B covers a conforming sphere spectrophotometer, so the procedure belongs in the report. The method treats material above 30% haze as diffusing and directs it to ASTM E167. Whatever standard applies, keep thickness, surface side, orientation, conditioning and specimen position constant. Clean dust and fingerprints without altering the surface, record whether protective liners were removed, and avoid unrepresentative scratches or bubbles unless those defects are the quality concern.
Instrument labels do not guarantee comparable haze
A color spectrophotometer can report haze only if its optical design and software support the required haze geometry and sequence. Compare instruments and sites using suitable reference materials and the same standard method.
Interpret the result with process knowledge
Surface haze
Can arise from texture, abrasion, coating condition or contamination.
Internal haze
Can relate to dispersion, crystallinity, phase separation, bubbles or particles.
Method variation
Can come from thickness, cleanliness, orientation, conditioning or instrument geometry.
Use haze beside a controlled transmission workflow, the correct optical mode and representative sampling.
Last reviewed 21/09/2026 · Level: Intermediate
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