Subjective Perception and Objective Measurement

The Standardization of Visual Effects in Glass



Photo of Caroline Lama

Caroline Lama

Vidaris, Inc.

Photo of Antonio Luz

Antonio Luz

Building Envelope Consultant - Senior Associate

Vidaris, Inc.

Photo of Ashley Reed

Ashley Reed

Eckersley O'Callaghan (EOC Engineers)



Current glass industry standards provide clear tolerances for readily quantifiable physical properties to assist with the evaluation of visual quality. Yet, these standards provide less definitive guidelines for properties that are subject to human perception. Such properties pose a complex challenge, as they require a reproducible means of quantifying an effect. Three visual effects (anisotropy, white haze, and color consistency) are considered with respect to present standards, underlying causes, and correlating physical properties. Methods of controlling subjective evaluation of these effects, including the standardization of viewing parameters and establishment of acceptable effect ranges to define defects, are outlined. The pairing of these methods with novel physical property measurement systems is proposed. Referencing techniques and models of soft metrology, in particular its application to color evaluation, can assist with the establishment of new glass industry standards to prevent visual effects from being dismissed as irreconcilable phenomena

Introduction - Industry Standards

Figure 1: Popping an iridescent bubble. Photo by Richard Heeks.

The glass industry has developed an array of standards to assist with the evaluation of visual quality. While these standards thoroughly

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Background - Qualitative Issues

Some of the qualitative topics that are often discussed in the glass industry are anisotropy, white haze and color consistency.

Generally speaking, anisotropy is the difference in a material’s properties

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Method - Quantification of Qualitative Issues

When one of these visual effects is deemed objectionable after installation on the building, thereby triggering a rejection and replacement of the glass, the cost and disruption can be significant

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Conclusion and Future Work

As professionals that are responsible for the quality of materials, including physical, performance, and visual properties, we are left lacking a standard method to evaluate a range of visual effects

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We would like to thank Peter Arbour, Dan Popadynec, and Israel Berger for their guidance on this paper.

Rights and Permissions

ASTM C1048-12 The Standard Specification for Heat-Strengthened and Fully Tempered Flat Glass, 2012.

ASTM D2244 Standard Practice for Calculation of Color Tolerances and Color Differences from Instrumentally Measured Color Coordinates, 2007.

BF Bulletin 006 Guideline to Assess the Visible Quality of Glass in Buildings, 2009.

BS EN 1863 Glass in Building - Heat-Strengthened Soda Lime Silicate Glass, 2011.

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Decourcelle, Dr. Romain, Kaminski, Guillaume, and Serruys, Francis. “Controlling Anisotropy” (accessed September 13, 2017).

Eugene, Christian. “Measurement of ‘total visual appearance’: a CIE challenge of soft metrology” 12th IMEKO TC1 & TC7 Joint Symposium on Man, Science & Measurement, 2008.

Glaston. “Measure and Reduce Tempered Glass Iridescence” (accessed September 13, 2017).

Glaston. “Killing the glass ghost: how to eliminate white haze from tempered glass?” (accessed September 19, 2017).

Glaston. “iLooK – Online glass quality measuring system“ (accessed September 28, 2017).

Weekes, Ian. “Glass Quench & Strain Marks” (accessed September 21, 2017).