Curtain Light-blocking Rate Testing

Curtain shading rate testing mainly conducts scientific testing and analysis on visible light transmittance, UV blocking rate, spectral transmittance curve analysis, shading uniformity evaluation, shading grade determination and material optical density determination, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for manufacturers' quality control and downstream users' product acceptance.

Testing Items

Visible light transmittance: This is the core indicator characterizing the shading performance of the curtain, referring to the ratio of the luminous flux passing through the curtain material to the incident luminous flux within the visible light wavelength range of 380-780 nm. The lower the value, the stronger the ability of the curtain to block the visible light. Usually, the visible light transmittance of the shading curtains is required to be lower than 0.5%-3%.

UV blocking rate: Evaluates the shielding ability of the curtain material against the ultraviolet rays (usually referring to the UVA and UVB bands). The high-shading curtains usually also have the excellent UV protection function, with the UV blocking rate reaching above 99%, which can effectively prevent the fading of the indoor fabrics and protect the skin health.

Spectral transmittance curve analysis: A spectrophotometer is used to measure the transmittance of the curtain material at the different wavelengths, plotting the complete spectral transmittance curve. This analysis can comprehensively understand the shading characteristics of the curtain within the whole spectrum range, and judge its filtering effect on the light of the specific wavelengths (such as the blue light).

Shading uniformity evaluation: Detects whether there are differences in the shading rate of the different parts of the curtain (such as the middle, edges and seams). This testing is particularly important for the large-area curtains. The uneven shading will cause the local light leakage, affecting the overall shading effect and use experience.

Shading grade determination: In accordance with the relevant standards (such as the industry practices or enterprise standards), the shading performance is divided into the different grades, for example, the first-grade shading (light transmittance <1%), second-grade shading (light transmittance 1%-3%) and third-grade shading (light transmittance 3%-5%), providing the intuitive reference for the consumers to purchase.

Material optical density determination: The optical density (OD value) is the logarithm of the reciprocal of the transmittance, used to more precisely describe the shading ability of the high-shading materials. The higher the OD value, the stronger the shading performance. For example, when the OD value is 3, the light transmittance is only 0.1%.

Testing Scope

Woven shading fabrics: Usually the high-density polyester, cotton and other materials are used as the base fabrics, and the shading is realized through the processes such as the coating, lamination or black core yarn weaving. The testing needs to pay attention to the influence of the coating uniformity, the peel strength of the composite layers and the distribution density of the black yarns on the shading rate.

Knitted shading fabrics: With the good elasticity and drape, the shading mostly relies on the compact loop structure or the finishing coating. The testing focus is on the stability of the shading rate under the tensile state and whether the coating cracks due to the elasticity, causing the light leakage.

Shading coated/composite curtains: The shading layers such as the PVC, acrylic or rubber are coated on the back of the ordinary fabrics, or a shading film is laminated. The testing needs to verify the adhesion of the coating/film, aging resistance and the shading performance retention rate after repeated folding.

Sandwich shading fabrics: The three-layer composite structure of "fabric + shading layer + lining" is adopted, and the shading layer is often the high-density black fabric or foamed coating. The testing needs to evaluate the bonding firmness between the layers and the shading uniformity of the overall structure.

Flocked shading curtains: The dense short fibre flocks are implanted on the base fabric to block the light. The testing needs to pay attention to the influence of the flock density, height and the lying direction on the light scattering and absorption, ensuring the shading effect.

Smart dimming curtains: Such as the electrochromic and PDLC (polymer dispersed liquid crystal) film curtains. In addition to the conventional shading rate, the testing scope also needs to include the special parameters such as the shading dynamic range under the different voltages/control states, response speed and power consumption.

Testing Methods

Spectrophotometric method: This is the most precise and standard laboratory testing method. A UV-visible spectrophotometer equipped with an integrating sphere is used. The curtain sample is placed at the sample port, and its transmittance spectrum within the specific wavelength (such as 550 nm) or the whole wavelength range is directly measured, thereby calculating the shading rate. This method has objective data and good repeatability.

Illuminance meter comparison method: A relatively simple on-site or rapid evaluation method. Under a stable light source, the reading of the light directly irradiating the illuminance meter (I0) and the illuminance reading after the light passes through the curtain (I1) are respectively measured, and the shading rate is calculated by the formula (1 - I1/I0) × 100%. Its precision is affected by the light source stability, measurement angle and ambient light.

Visual sensory evaluation method: In a dark room, a light source with a standard intensity (such as a flashlight with a specific lumen value) is used to closely irradiate the back of the curtain, and the light transmission situation is observed from the front. This method is highly subjective, and is usually used for the preliminary screening or the grade comparison with the standard sample photos, and cannot replace the quantitative testing.

Multi-layer stacking testing method: For the ultra-thin curtains or the curtains with the weak shading performance, the shading rates in the single-layer and multi-layer stacking states can be tested, to evaluate the potential of improving the shading effect by increasing the number of layers in the actual use, and provide the use suggestions for the consumers.

Ambient light simulation testing method: In an artificial climate chamber or an experimental chamber simulating the indoor and outdoor light environments, the overall shading effect of the curtain under the actual application scenarios (such as the noon sunlight and evening scattered light) is tested, evaluating its influence on the visual comfort of the human eyes, with more practical reference value.

Retest after the durability testing: After the aging tests such as the light fastness, washing and friction are carried out on the curtain samples in accordance with the standards, the shading rate is measured again, to evaluate the durability and quality reliability of the shading performance of the product, preventing the sharp decline of the shading effect after use.

Testing Standards

Domestic Standards:

1. GB/T 19817, Textiles — Decorative fabrics

2. GB/T 8427, Textiles — Tests for colour fastness — Colour fastness to artificial light: Xenon arc fading lamp test

3. GB/T 3920-2024, Textiles — Tests for colour fastness — Colour fastness to rubbing

4. GB 18401-2010, National general safety technical code for textile products

5. GB/T 3921-2008, Textiles — Tests for colour fastness — Colour fastness to washing with soap or soap and soda

6. GB/T 3922-2013, Textiles — Tests for colour fastness — Colour fastness to perspiration

7. GB/T 2910, Textiles — Quantitative chemical analysis

8. GB/T 7573-2009, Textiles — Determination of pH of the aqueous extract

International Standards:

1. ISO 105, Textiles — Tests for colour fastness

2. ISO 105-B02, Textiles — Tests for colour fastness — Part B02: Colour fastness to artificial light: Xenon arc fading lamp test

3. ISO 13934-1, Textiles — Tensile properties of fabrics — Part 1: Determination of maximum force and elongation at maximum force using the strip method

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

UV-visible spectrophotometer (with integrating sphere): The core testing equipment. The integrating sphere ensures the collection of all the transmitted and scattered light, obtaining the accurate transmittance data. The wavelength range of the equipment needs to cover the UV and visible light regions, with the high resolution, and is regularly calibrated with the standard plates, to ensure the reliability of the measurement results.

Standard light source and dark box: Provide the stable, uniform lighting conditions with the known spectral power distribution (such as the D65 standard light source), combined with the optical dark box to eliminate the interference of the ambient stray light, creating the standardized testing environment for the illuminance meter comparison method or sensory evaluation, improving the comparability of the testing results of the different batches.

Digital illuminance meter: Used for the illuminance meter comparison method. The illuminance meters with the wide range, high precision and good cosine correction performance should be selected, and the probes need to be regularly calibrated. During the measurement, the probe needs to be kept close to the sample and maintain the fixed geometric relationship with the light source, to reduce the errors.

Sample cutting and fixing devices: Including the standard cutters, sample holders or frames. Ensure that the measured sample is flat and wrinkle-free, and the edges are well sealed, preventing the light leakage from the edges of the sample from affecting the measurement accuracy, which is particularly crucial for the light and thin fabrics.

Optical densitometer: An instrument specially used to measure the optical density (OD value) of the high-shading materials, usually based on the transmission measurement principle. For the products claiming the "full shading" or "100% shading", the optical densitometer can detect the extremely small amount of light transmission more sensitively.

Durability testing equipment: Such as the xenon lamp weathering test chamber (simulating the sunlight aging), friction testing machine and household washing machine. They are used to evaluate the retention rate of the shading performance of the curtain materials after the accelerated aging or simulated use, and are the key auxiliary equipment for evaluating the long-term quality of the product.