The following is an approximate and general comparison table of Visible Light Transmittance (VLT) and clarity differences among “Clear,” “Super Clear,” and “Clear Plus” glass types in both raw and tempered states for architectural applications (e.g., 10mm glass):
| Glass Type | State | Visible Light Transmittance (%) | Description |
| Clear | Raw | 85 – 90 | Raw glass without special coatings or technology |
| Clear | Tempered | 80 – 85 | Slight reduction in light transmittance due to thermal processing and structural changes |
| Super Clear | Raw | 90 – 95 | Maximum clarity with minimal color distortion |
| Super Clear | Tempered | 85 – 90 | Slight reduction in light transmittance, yet remains highly transparent |
| Clear Plus | Raw | 90 – 95 | Advanced technology with lower color distortion and superior clarity |
| Clear Plus | Tempered | 85 – 90 | Reduced light transmittance, but maintains high transparency |
- Light Transmittance Reduction in Tempered State: The tempering process (thermal strengthening) typically alters the glass structure, resulting in a slight decrease in light transmittance, though this reduction is usually marginal.
- The Goal of Tempering: To increase safety and resistance to breakage, not to cause a significant change in transparency.
- Minor Variations: In specific models or those with different coating technologies, the transmittance percentage may vary slightly.
- Standard Reduction: The decrease in light transmittance for tempered glass compared to raw glass is typically about 2% to 5%. This reduction is caused by changes in optical structure and surface refractions during the tempering process.
What is the reduction in light transmittance for glass tempered with the GLASTON RC350 Vortex Pro-Convection European furnace compared to raw glass? The type of process and heat control in modern furnaces, such as the GLASTON RC350 Vortex Pro-Convection, play a major role in minimizing this effect; therefore, a reduction of approximately 1% is typical.
What is the average reduction in light transmittance for glass produced in other furnaces?
The average reduction in light transmittance for glass tempered in other furnaces is approximately 2% to 5%. Furthermore, depending on the technologies used in these furnaces, the final clarity may be affected to some extent.
