Do Exterior HPL Panels Fade?

Understanding Delta E, Grey Scale and Colour Stability in Exterior HPL Facades

When selecting façade materials, one of the most common and practical questions is:

Do Exterior HPL panels fade over time?

This question is directly linked to UV resistance, colour stability, and long-term durability of façade panels.

Exterior HPL panels are constantly exposed to:

Ultraviolet (UV) radiation
Temperature fluctuations
Rain and humidity
Pollution and environmental exposure

Over time, these factors can affect colour performance, leading to:

Colour fading
Loss of vibrancy
Uneven ageing across panels

However, in high-quality systems like those from Samrat HPL, colour change is not random—it is scientifically measured, controlled, and minimized.

With over 9 million m² of Exterior HPL installed globally till 2025, Samrat HPL panels have demonstrated reliable weather-resistant façade performance and long-term colour stability.

What Is Colour Fading in Exterior HPL?

Colour fading refers to the change in appearance of a surface due to prolonged exposure to sunlight and environmental conditions.

In façade materials, fading occurs due to:

UV-induced degradation of pigments
Breakdown of molecular structures
Surface wear over time

This is why UV resistance in HPL panels is one of the most critical performance parameters.

How Is Colour Change Measured Scientifically?

Instead of relying on visual judgement, colour stability is measured using:

Delta E (ΔE) – Numerical Measurement
Grey Scale – Visual Assessment

These two methods together provide a complete evaluation of colour performance in exterior façade panels.

What Is Delta E (ΔE)?

Delta E (ΔE) is a numerical value that represents the difference between two colours.

It is measured using a spectrophotometer, based on the CIELAB colour system:

L* → Lightness
a* → Red–Green axis
b* → Yellow–Blue axis

ΔE represents the distance between two colours in 3D colour space.

Interpretation of Delta E Values

ΔE Value Meaning in Real Applications
0–1 No visible difference
1–2 Slight change
2–3 Noticeable on close inspection
3–5 Clearly visible

In Exterior HPL Context

After UV exposure or weathering tests:
Low ΔE → High colour stability
High ΔE → Visible fading

This is why ΔE is widely used in evaluating HPL façade colour durability.

What Is Grey Scale?

Grey Scale is a visual method used to assess colour change.

It compares a tested sample against standardized grey references.

Grey Scale Ratings

Grade – Performance
5 – No visible change
4 – Slight change
3 – Noticeable change
2 – Significant change
1 – Severe fading

Why Grey Scale Matters

While ΔE is scientific, Grey Scale reflects:

Human visual perception
Real façade appearance
Practical acceptance criteria

Why Do Some HPL Panels Fade Faster?

Not all façade panels perform equally.

Colour fading depends on several technical factors:

Pigment Type
Organic pigments → higher fading risk
Inorganic pigments → better UV stability

➡️ Related blog
Organic vs Inorganic Pigments in Exterior HPL

UV Protection Layer (PMMA)

At Samrat HPL:
50-micron PMMA (Plexiglas®) layer from Evonik / Röhm

This layer:
Reduces UV radiation reaching pigments
Improves colour stability
Lowers ΔE values

➡️ Related blog
How PMMA (Acrylic) Layers Improve Exterior HPL Performance

Decorative Paper Quality

Samrat HPL uses papers from:
Technocell
Munksjö
Schattdecor

This ensures:
Better pigment stability
Uniform colour behaviour
Reduced fading risk

Manufacturing Quality

Samrat HPL panels are produced with:
100% phenolic resin system
Higher resin content (~28.5%)
High-density structure

This improves:
Pigment encapsulation
Structural stability
Resistance to environmental degradation

How Testing Is Done: Xenon Weathering

To simulate real-world exposure, panels undergo:

3000-hour Xenon Arc Weathering Test

This replicates:
Sunlight (UV radiation)
Heat cycles
Moisture exposure

After testing:
ΔE is measured
Grey Scale rating is assigned

This ensures scientifically validated colour performance.

What Does This Mean for Real Facades?

From a practical standpoint:
Low ΔE → façade looks consistent for years
Grey Scale 4–5 → minimal visible change

This ensures:
Uniform appearance across panels
Reduced maintenance
Long-term architectural aesthetics

Real-World Performance – Samrat HPL

With over 9 million m² installed globally till 2025, Samrat HPL panels perform reliably in:
High UV regions (Middle East)
European climates
Coastal environments

This demonstrates long-term UV resistance and colour stability in façade panels.

Why Architects Prefer Samrat HPL

Samrat HPL ensures:
Controlled colour change (low ΔE)
High Grey Scale ratings
UV-resistant façade panels
Weather-resistant cladding performance

This delivers both:
Scientific reliability
Visual consistency

Conclusion

So, do Exterior HPL panels fade?

👉 Yes—but only within controlled, measurable, and acceptable limits.

With proper engineering, fading becomes:
Predictable
Minimal
Uniform across panels

Through:
Advanced pigment systems
PMMA UV protection
High-quality decorative papers
Xenon weathering validation

Samrat HPL Exterior Cladding ensures façade panels that do not fade significantly and maintain long-term colour stability.

Backed by 9 million square metres of global installations till 2025, Samrat HPL continues to deliver weather-resistant, durable, and colour-stable façade solutions.

Do Exterior HPL Panels Fade? Colour Stability Explained