What is Solar Radiation Testing on Products and Materials?

We never think about it, but many of the objects around us are exposed to sunlight for several hours a day. Solar radiation has a significant impact on many of the products and materials we use every day. From the plastic in garden furniture to car upholstery, to the fabrics used in clothing; just to name a few.

For this reason, solar radiation testing is essential to ensure the durability and reliability of many products and is used in various manufacturing sectors.

Today we will describe the solar radiation test and the laboratory instrument with which we perform it: the illumination chamber. 

What is Solar Radiation?

By solar radiation, we mean the energy emitted by the sun in the form of light, which in turn is divided into visible, ultraviolet (UV), and infrared (IR) light. Although it is the basis of life, prolonged exposure to solar radiation can cause various types of damage to materials. For example, UV rays can degrade polymer molecules, making plastics brittle and prone to cracking, while visible and IR light can heat materials, causing thermal expansion and structural changes. 

For this reason, it is necessary to understand the effect of solar radiation on every type of product and material and conduct a rigorous series of tests to verify the limitations and any design flaws.

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Solar Radiation Tests

The various solar radiation tests deal precisely with this.

To conduct them, there is a special laboratory instrument called an illumination chamber.

The illumination chamber is a particular type of climatic chamber that, in addition to being able to alter and monitor the temperature and relative humidity parameters inside it, has different lighting sets that simulate exposure to solar radiation.

Solar radiation testing procedures are outlined by a series of standards issued by internationally recognized bodies, such as ISO, the International Organization for Standardization.

Among these we can mention ISO 4892-2 and ISO 16474-1:2013, which regulate the tests for solar exposure of plastic materials and paints and varnishes respectively.

How the Solar Radiation Test Works

Solar radiation tests are conducted by placing a sample of the product or material being tested and exposing it to solar radiation for a predetermined period of time or a series of cycles. 

Okay, but what kind of radiation?

There are several types of lamps that simulate a variety of solar radiation intensities. The most common are the following:

• UV (Ultraviolet) Lamps: As the name suggests, these lamps emit only the ultraviolet part of the light spectrum. They are used to evaluate polymer degradation, loss of elasticity, and other physical and chemical changes caused by UV radiation. They are particularly used to test plastics, coatings, and fabrics.

• Xenon Lamps: Xenon lamps are designed to replicate the full spectrum of sunlight, including visible light and some infrared radiation. Consequently, they test how materials react to full sunlight, including color changes, aging, and thermal resistance.

• Fluorescent Lamps: These lamps emit light that simulates indoor artificial lighting conditions. They are used to test materials intended for indoor environments, where direct sunlight is limited. They are therefore essential for assessing the effect of artificial lighting on materials and products intended primarily for use inside buildings.

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The FDM Illumination Chamber

FDM – Environment Makers has been a consolidated presence in the field of environmental testing for over 70 years.

Our climatic and environmental chambers can be equipped with Solar Boxes to perform all tests on products and materials in accordance with the aforementioned standards.

Furthermore, our lighting chambers can be equipped with various lighting sets that can be arranged inside the chamber according to the customer's needs. In addition to the lamps we've discussed, FDM lighting chambers also include specific lamps for growing organisms, such as BioLamp and ArabLamp. The latter was specifically designed for growing Arabidopsis. We've discussed it here.

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Discover the FDM solution for solar aging testing: our Xenon light test chamber simulates solar radiation with a 1600W Xenon lamp, compliant with ISO 11341 and ASTM G155.

Reference Standards

• MIL-STD-810H Method 505.7 — Solar Radiation (Sunshine) test procedures
• IEC 60068-2-5 — Test Sa: Simulated solar radiation at ground level
• ISO 4892-1/2/3/4 — Plastics — Methods of exposure to laboratory light sources (xenon, carbon-arc, UV fluorescent)
• ASTM G155 — Standard Practice for Operating Xenon Arc Light Apparatus
• SAE J1960 / SAE J2527 — Accelerated exposure of automotive exterior materials (xenon arc)
• ISO 105-B02 — Textiles — Color fastness to artificial light (xenon arc)

Authoritative Sources

• ASTM G155 — Xenon arc apparatus standard.
• IEC 60068-2-5 — Solar radiation simulation at ground level.
• WMO — World Meteorological Organization — Global irradiance reference data.

Frequently Asked Questions About Solar Radiation Testing

What is the difference between solar radiation test and ICH photostability test?

The solar radiation test (MIL-STD-810 Method 505, IEC 60068-2-5) simulates the entire solar spectrum (UV+Vis+IR, 300-3000nm) with an irradiance of 1120 W/m² and evaluates mechanical, thermal, and chromatic degradation of materials. The pharmaceutical photostability test (ICH Q1B) uses only UV-Vis (320-800nm) with a fixed dose of 1.2 million lux·hour + 200 Wh/m² UV to highlight photodegradation of active molecules. Applications and durations are different: solar = days/weeks, photostability = 24-96h.

How is solar radiation simulated in a climate chamber?

Two main technologies: xenon lamps with daylight filters (full spectrum 290-3000nm, more realistic but expensive) and metal halide / HMI (high power, typically for solar photovoltaic simulator testing). Control parameters: total irradiance (W/m²), spectral distribution, black panel temperature (BPT) up to 100°C, and ambient temperature 25-55°C. Standards define light/dark cycles (20h on + 4h off MIL-STD-810) or steady state (IEC 60068-2-5).

For which products is testing mandatory?

Automotive: Vehicle interiors (steering wheels, dashboards, seat fabrics) with xenon and SAE J2412 1250h cycles. Vehicle exteriors: Paints, chrome, plastics with SAE J2527 5000h. Building: Windows, facades, exterior paints with EN ISO 11431. Textiles: Color fastness to light ISO 105-B02. Photovoltaic panels: IEC 61215 UV test 15 kWh/m². Pharmaceuticals: ICH Q1B for photosensitive drugs.

Difference between Class A, B, and C solar simulators?

IEC 60904-9 and ASTM E927 classifications for photovoltaic simulators: Class A highest accuracy (spectral match 0.75-1.25, uniformity ±2%, stability ±2%) — used for module qualification and certification. Class B intermediate (0.6-1.4 / ±5% / ±5%) — R&D and quality control testing. Class C (0.4-2.0 / ±10% / ±10%) — rapid screening. A solar simulation test in a certified PV laboratory requires Class A or AAA.