Quartz Glass Transmittance Testing: Methods, Standards, and Result Interpretation

Quartz glass is widely used in optics, semiconductors, UV equipment, and scientific instrumentation due to its exceptional transparency and thermal stability. Evaluating its transmittance is essential for quality control and application-specific performance. This article explains the common testing methods, relevant standards, and how to interpret the results.

1. Testing Methods

The most widely used technique is spectrophotometry, which measures how much light passes through a quartz sample at different wavelengths. UV–Vis–NIR spectrophotometers can cover ranges from deep ultraviolet to near infrared, offering a full picture of optical behavior. Before measurement, samples must be cleaned to eliminate fingerprints and surface residues that could artificially reduce transmittance. For high-precision applications, double-beam spectrophotometers help minimize instrument drift and background interference.

Another method is laser transmission testing, often used in industries requiring extremely stable monochromatic light. This technique provides high accuracy at specific wavelengths such as 254 nm, 365 nm, or 1064 nm.

2. Applicable Standards

International standards such as ISO 9050, ASTM E903, and JJG 178 provide guidelines on measurement procedures, sample thickness, calibration, and data calculation. These standards ensure comparability between different batches and manufacturers. In most cases, quartz glass should show transmittance above 90% in visible wavelengths, with fused quartz showing particularly strong UV performance.

3. How to Interpret the Results

Higher transmittance indicates fewer impurities, better melting quality, and smoother surfaces. A noticeable drop at specific wavelengths may suggest internal bubbles, metallic impurities, or surface micro-cracks. Consistency across multiple samples indicates stable manufacturing quality, while large variations may point to process control issues.

Conclusion

Transmittance testing provides crucial insights into the optical quality of quartz glass. By understanding the methods, standards, and interpretation guidelines, users can better evaluate whether a product meets the requirements of high-precision optical applications.