Detection of the transmission rate of the medium

Transmittance of the Medium – Optical Properties Testing for Glazing, Films, Liquids and Solar Components

As an ISO/IEC 17025 accredited (CNAS) independent laboratory, we provide specialized transmittance of the medium testing services for manufacturers, importers, and quality control laboratories in Algeria. Transmittance — the fraction of incident light or electromagnetic radiation that passes through a material — is a critical performance parameter for architectural glass, automotive glazing, photovoltaic modules, greenhouse films, packaging materials, optical components, and liquid media (coolants, process water, pharmaceutical solutions). Our measurements cover ultraviolet (UV), visible (VIS), near‑infrared (NIR), and sometimes mid‑infrared (MIR) or solar spectral ranges, depending on the application. We help clients verify optical specifications, diagnose color or clarity issues, assess degradation after weathering, and comply with local and international standards for safety glazing and energy efficiency.

Types of Samples and Media We Test

• Architectural glass (clear, tinted, low‑E coated, laminated, tempered, insulated glass units)
• Automotive glazing (windshields, side windows, rear windows, sunroofs, laminated safety glass)
• li>Photovoltaic glass (front cover glass for solar panels, anti‑reflective coated glass)
• Plastic films and sheets (polycarbonate, acrylic – PMMA, PET, polyvinyl butyral – PVB, ethylene vinyl acetate – EVA encapsulant)
• Agricultural films (greenhouse cover films, mulching films, UV‑blocking or UV‑transmitting films)
• Packaging materials (transparent plastic bottles, blister packs, display windows, food wrap films)
• Liquid samples (cooling water, heat transfer fluids, pharmaceutical solutions, inks, dyed liquids, beverages, process chemicals)
• Optical components (lenses, prisms, beam splitters, filters, optical windows, fiber optic materials)
• Transparent ceramics (sapphire, spinel, aluminum oxynitride – ALON, yttria – Y₂O₃)
• Smart window materials (electrochromic, photochromic, thermochromic coatings on glass or film)
• Protective coatings and anti‑reflective layers applied to transparent substrates

Spectral Ranges and Measurement Geometries

• Ultraviolet (UV) range (200–400 nm) – Critical for assessing UV blocking or transmission through sunscreens, automotive glazing (protection of interior materials), greenhouse films (control of plant growth), and UV‑curable coatings. We also measure UV transmittance for medical and laboratory applications (e.g., quartz cuvettes, UV disinfection equipment).
• Visible range (380–780 nm or 400–700 nm) – Corresponds to human vision. Used for color measurement (CIELAB coordinates, yellowness index, clarity, haze), luminous transmittance (Tv) for windows and windshields, and assessment of optical clarity of packaging materials. Visible transmittance directly affects daylighting, glare, and visual comfort in buildings and vehicles.
• Near‑infrared (NIR) range (780–2500 nm) – Important for solar control (heat rejection). Low NIR transmittance is desirable in hot climates like Algeria to reduce solar heat gain through windows. High NIR transmittance is needed for certain agricultural films (to promote plant photosynthesis and temperature control) and for photovoltaic modules (to capture solar energy).
• Full solar spectrum (300–2500 nm) – Integrated solar transmittance (Tₛₒₗ) is calculated by weighting the spectral transmittance against the standard solar irradiance spectrum (AM1.5G). This value determines the total solar energy transmitted through a glazing or film, essential for energy efficiency ratings.
• Specific narrow bands (e.g., 550 nm, 850 nm, 1064 nm) – For laser safety goggles, optical filters, or sensors. We measure transmittance at customer‑specified single wavelengths with narrow bandwidth (typically ±2 nm or ±5 nm).
• Normal incidence (0°) and off‑angle measurement (up to 60°) – Transmittance often depends on the angle of incidence. For automotive windshields (angled installation) and architectural glass (varying sun angles), we measure transmittance at multiple angles (typically 0°, 15°, 30°, 45°, 60°) to evaluate performance under real‑world conditions.
• Diffuse and regular (specular) transmittance – For transparent media, regular transmittance (straight‑through light) dominates. For translucent or scattering materials (frosted glass,某些 diffusers, textured films), we measure total transmittance (including scattered light) using an integrating sphere. The ratio of diffuse to total transmittance (haze) is also reported for clarity evaluation.

Instrumentation and Measurement Methods

• UV‑Vis‑NIR spectrophotometer with double‑beam configuration – Our primary instrument covers the range from 200 nm to 3300 nm with a resolution of 1–5 nm (adjustable). Double‑beam design compensates for lamp drift and atmospheric absorption, ensuring high stability. Light source: deuterium lamp (UV) and tungsten‑halogen lamp (VIS‑NIR). Detectors: photomultiplier tube (UV‑VIS) and PbS or InGaAs (NIR).
• Integrating sphere attachment (for total transmittance and haze measurement) – A 150 mm diameter sphere coated with high‑reflectivity BaSO₄ or Spectralon collects both transmitted specular and scattered light. The sphere includes a port for excluding the specular component to measure diffuse transmittance only. This configuration complies with international standards for haze measurement (ASTM D1003, ISO 13468).
• Temperature‑controlled sample holders (for liquids and temperature‑sensitive materials) – For measuring transmittance of liquid media as a function of temperature (e.g., coolant transmittance at 80°C for solar thermal systems). The sample compartment is equipped with a Peltier or circulating water bath, controlling temperature from 5°C to 95°C with an accuracy of ±0.5°C.
• Variable angle transmission stage (gonio‑transmission) – A motorized rotation stage allows positioning of the sample at precise angles (0° to 80° in 0.1° increments). This is essential for automotive glazing and for measuring transmittance of anti‑reflective coatings designed for off‑normal incidence.
• Polarization attachment (for measuring polarized transmittance) – A Glan‑Taylor or wire‑grid polarizer is placed in the incident beam to measure transmittance for s‑polarized and p‑polarized light. Used for optical components in polarized light systems (LCD displays, certain sensors).
• Large sample holder (up to 500 mm × 500 mm) – For field samples such as glass panels, plastic sheets, or solar modules that cannot be cut down. The spectrophotometer is equipped with an external sample compartment and a long light path (up to 2 m) to accommodate large‑format samples.

Key Parameters Calculated and Reported

• Luminous transmittance (Tv, in %) – Weighted average of spectral transmittance over the visible range using the photopic vision function V(λ) (CIE 1924 standard observer). Values range from 0% (opaque) to near 100% (perfectly clear glass). For automotive windshields, the minimum required luminous transmittance is typically 70% (in many countries, including Algeria’s regulations based on UNECE R43).
• Solar transmittance (Tₛₒₗ, in %) – Weighted average of spectral transmittance (300–2500 nm) against the AM1.5G reference solar spectrum. Used to calculate solar heat gain coefficient (SHGC) or g‑value of glazing. A lower Tₛₒₗ is desirable for hot climates to reduce cooling loads.
• Ultraviolet transmittance (Tᵤᵥ, in %) – Weighted according to the erythemal action spectrum (sunburn risk) or measured as simple average over UVA (315–400 nm) and UVB (280–315 nm) bands. For automotive glazing, UV transmittance is typically limited to below 5% to protect occupants and interior materials.
• Haze (in %) – The percentage of transmitted light that is scattered more than 2.5° from the incident beam direction. Low haze (<1%) is required for high‑clarity applications (display glass, optical lenses). Haze between 2–5% is acceptable for architectural glass, while diffusing films may have haze >50%.
• Clarity (or distinctness of image – DOI) – Assessed from narrow‑angle scattering measurements. Clarity affects the sharpness of objects viewed through the material. Measured according to ASTM E430 or similar procedures.
• Color coordinates (CIELAB L*, a*, b*) – Calculated from the visible transmittance spectrum using a standard illuminant (D65 for daylight, A for incandescent, or F series for fluorescent light). ΔE (color difference) between a test sample and a reference sample can be computed. A greenish or bluish tint may be acceptable for certain glass, while neutral gray is typically required for automotive windshields.
• Yellowness index (YI) – Calculated according to ASTM E313. Indicates yellowing due to UV degradation, thermal aging, or plasticizer migration. Used for quality control of transparent polymers (polycarbonate, acrylic, PET, EVA).
• Selectivity (ratio of Tv to Tₛₒₗ) – A high selectivity (Tv / Tₛₒₗ > 1.5) indicates that the glazing allows visible light in while blocking a large portion of solar infrared (low‑E glass). Highly selective glazing is very effective for energy‑efficient buildings in hot climates.

Application‑Specific Testing

• Automotive glazing transmittance (windshield, side windows, rear windows) – We measure luminous transmittance (Tv) at normal incidence and at angles simulating typical installation (windshield: 30–45° from horizontal). For windshields, the typical requirement is Tv ≥ 70% when new, and ≥ 65% after aging (wear, abrasion). UV transmittance must be ≤ 5% for all glazing (UNECE R43). Visible light transmittance of side windows may be regulated by Algerian traffic laws (typically ≥ 70% for front side windows).
• Photovoltaic glass transmittance (solar cover glass) – We measure spectral transmittance from 300 nm to 1200 nm (relevant for silicon solar cells). The integrated transmittance weighted by the AM1.5G spectrum indicates the amount of light reaching the photovoltaic cell. Anti‑reflective coated glass should achieve transmittance > 93% over the 400–1000 nm range. Low iron glass can exceed 91% transmittance. We also measure transmittance after damp heat (85°C / 85% RH) and UV preconditioning to simulate service life.
• Agricultural greenhouse film transmittance – We measure photosynthetically active radiation (PAR) transmittance (400–700 nm) which drives plant growth. UV transmittance (controlled for disease prevention or pollinator guidance). NIR transmittance (for temperature control inside the greenhouse). Diffuse transmittance (haze) is important for light scattering to reach lower leaves. Some films are designed to be UV‑blocking (materials exposed to the outdoor environment in Algeria’s high UV index region require long‑term stability).
• Liquid medium transmittance (cooling water, pharmaceutical solutions, process chemicals) – We measure transmittance in standard 10 mm pathlength quartz cuvettes at specified wavelengths (e.g., 660 nm for clarity, 254 nm for UV disinfection monitoring). For cooling water used in industrial plants, low transmittance indicates suspended solids, microbiological growth, or dissolved color bodies. We also measure the effect of temperature on liquid transmittance (for solar thermal fluids, the transmittance at 80–120°C affects absorber efficiency).
• Packaging material transmittance (transparent bottles, blisters, display packaging) – We measure luminous transmittance and haze to verify optical clarity. UV transmittance is important for products sensitive to light degradation (pharmaceuticals, cosmetics, certain foods). For food packaging, transmittance may be measured after exposure to simulated sunlight (xenon arc) to assess color stability.
• Smart window material transmittance (electrochromic, photochromic, thermochromic) – We measure transmittance in different states: bleached (clear) and colored (darkened). The dynamic range (Tₗₑₐᵣ / Tₙₐᵣᵣₒw) is calculated. Switching speed (time to change from clear to dark) is measured by time‑resolved transmittance. Hysteresis (difference between darkening and clearing curves) is also reported. For thermochromic materials, we measure transmittance as a function of temperature (25°C to 100°C).
• Optical component transmittance (lenses, filters, windows) – For laser optics, we measure transmittance at the specific laser wavelength (e.g., 1064 nm, 532 nm, 355 nm) with high spectral resolution (±1 nm). Tolerance is typically ±0.5% absolute for anti‑reflection coated optics. For bandpass filters, we measure peak transmittance and center wavelength drift.

Environmental Conditioning and Durability Testing

• UV aging and transmittance loss – Samples (especially plastic glazing and agricultural films) are exposed to UV fluorescent lamps (UVA‑340 or UVB‑313) or xenon arc (simulating full sunlight) for 500, 1000, 2000 hours. Transmittance is measured at intervals. Acceptable loss of luminous transmittance for automotive glazing is typically ≤ 2% after 1000 hours UV exposure.
• Damp heat exposure (85°C / 85% RH) – For photovoltaic glass encapsulants (EVA, POE) and laminated glazing (PVB, ionoplast interlayers), we expose samples to damp heat for 1000 hours and measure transmittance before and after. Reduction in transmittance indicates delamination, yellowing, or corrosion of coatings.
• Thermal cycling (e.g., -40°C to +85°C, 100 cycles) – Simulates seasonal and diurnal temperature changes. Transmittance is measured after thermal cycling to detect permanent changes (cracking, delamination, haze increase).
• Abrasion and wear testing (Taber abraser or falling sand) – For plastic glazing (polycarbonate, acrylic) used in outdoor applications, we measure transmittance and haze before and after abrasion. The change in haze (ΔHaze) is reported. An abrasion‑resistant coating should show ΔHaze < 5% after 500 cycles with a CS‑10 wheel.
• Chemical resistance (exposure to cleaning agents, fuels, oils, acids, alkalis) – For glazing and films that may come into contact with chemicals, we measure transmittance before and after immersion in specified liquids for 24–168 hours. A change in luminous transmittance > 2% is typically considered a failure.
• Condensation and water immersion (for sealed insulating glass units) – We measure transmittance before and after exposure to high humidity or water immersion to detect fogging or internal moisture penetration.

Reporting and Deliverables

Each transmittance of the medium test report includes the following information:

• Sample identification (material type, thickness, color, surface texture, any coatings, manufacturer or supplier if known)
• Measurement conditions: spectral range (nm), wavelength interval (data spacing), angle of incidence (degrees), polarization state (if applicable), temperature (°C), sample condition (as‑received, after conditioning, after environmental exposure)
• Spectral transmittance data: tabulated transmittance values (typically every 1 nm, 2 nm, 5 nm, or 10 nm depending on the range) and a plotted transmittance curve (transmittance % versus wavelength in nm)
• Calculated parameters: luminous transmittance (Tv, %), solar transmittance (Tₛₒₗ, %), ultraviolet transmittance (Tᵤᵥ, %), haze (%), clarity (or DOI), color coordinates (L*, a*, b*) under specified illuminant, yellowness index (YI), selectivity (Tv / Tₛₒₗ), integrated values in specific wavelength bands
• For environmental aging tests: transmittance values before and after exposure, calculated change (ΔTv, ΔTₛₒₗ, ΔYI, ΔHaze), and commentary on observed degradation (yellowing, delamination, scratching)
• Comparison with client‑supplied acceptance criteria (if provided)
• Raw data files (ASCII or CSV format) and instrument calibration records are available upon request

No statement of compliance with any external standard or regulation is made unless the client has provided specific pass/fail criteria in writing. All raw data and retained samples are stored in our quality management system for a minimum of 10 years.