Infrared, Emissivity, and Black Coatings: Clearing Up Common Misunderstandings
When engineers talk about “black coatings,” they often mean very different things. Some think in terms of aesthetics, others of visibility, and many about infrared absorption or stray light suppression. But in precision fields—from aerospace to photonics—words like “black,” “emissive,” and “infrared absorbing coating” must be treated with care.
This paper unpacks the most common misconceptions around infrared optics, emissivity, low reflectance black paint, and ultra-black materials—offering clarity and practical engineering advice.
Misconception 1: Assuming "Black" Means Infrared Absorbing
To the human eye, matte black paint looks very black. But many such paints actually reflect near-infrared (NIR) wavelengths—especially around 905 nm and 1550 nm, where LiDAR and IR sensors operate.
Tip: True infrared absorbing coatings require materials tested and tuned for those specific wavelengths.
Many popular materials—even those marketed as super black coatings and—can fail at IR suppression if not properly selected validated with the vendor. This includes well-known names like Vantablack, Acktar Black and Singularity Black. Each should be chosen based on reflectance levels and emissivity at specific wavelength and of course environmental and durability needs.
Misconception 2: Thinking Emissivity = Color or Absorption
Emissivity is not the same as absorption, and it is not directly related to how visually black a material appears. Emissivity specifically describes how efficiently a surface radiates thermal energy—typically in the infrared range.
- A surface can absorb visible light and appear very black, yet have low emissivity in IR.
- Some materials with high IR emissivity may not appear dark at all.
This confusion often leads engineers to overestimate a material’s thermal radiation capabilities just because it looks black or has high absorptivity in the visible range.
Think of emissivity as “how well it emits heat,” not “how black it looks.”
Some coatings are designed to radiate heat effectively (high emissivity), while others are intended to block thermal transfer (low emissivity). This distinction is critical in thermal systems, satellite design, and sensor housings.
Misconception 3: Using the Wrong Coating for the Application
Some engineers specify “high emissivity” without checking whether their system operates in visible, SWIR, or LWIR.
Always ask:
- What is the operating wavelength?
- Do I need low reflectance, high emissivity, or both?
- Will the surface be exposed to vacuum, heat, or cleanroom environments?
Matching the coating to the optical and thermal profile of the system can dramatically improve performance.
Misconception 4: Confusing Simulations with Reality
Modern optical software (like Zemax, FRED, LightTools) can simulate stray light paths. But real-world systems still suffer from ghosting and back-reflections.
That’s why many engineers still turn to physical testing, especially since built parts often differ from designed ones and blackening coatings can perform not as specified
Best practice: Always check dimensions and optical properties of the actual “as- build”, “as-coated” parts.
Terms Engineers Should Use More Precisely
Term | What It Should Mean |
Black | Absorbs light across UV-VIS-IR, not just visually dark |
High Emissivity | Emits thermal radiation efficiently—typically IR range |
Low Reflectance | Suppresses stray light; may not emit heat well |
Infrared Absorbing | Specifically engineered to absorb near/mid/far IR |
Diffuse Black | Scatters and absorbs light; ideal for optical traps |
Specular Black | Low reflectance at direct angles; sometimes desired to direct known reflections |
Final Thoughts
Engineers designing optical systems, LiDAR, or infrared sensors must be precise. Using the wrong black coating—whether its darkest black paint—can lead to serious performance issues.
Coatings must be chosen based on their optical, thermal, and material properties, not just appearance or brand.
Example Solution: Acktar’s Hybrid Approach
Acktar offers a suite of coatings that address many of these challenges:
- Fractal Black™ – Wide-spectrum low reflectance + high emissivity
- Nano Black™ – Black in VIS but low emissivity for shielding or no heat radiation to the sensitive components
- Lambertian Black™ foil and patches – For quick testing, prototyping, and localized suppression
All are non-outgassing, vacuum-compatible, and suitable for space and cleanroom environments.
Do you have a question? Our experts will be happy to hear from you and advise you on the best product for you. Contact Us.
The use of Acktar coatings yield major improvements in a wide range of products and applications.
Visit the following links to find use cases by categories:
