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AGNORA, a leading fabricator of high-quality oversized architectural glass and complex glass project (stairways, bridges, art projects) and Louis Moreau, Head of Technology and Innovation at AGNORA recently chaired the task group that wrote the first standard method to measure anisotropy in architectural glass, ASTM C1901-21.

The purpose of the new standard is to provide a repeatable test method to measure the optical anisotropy of architectural glass.  The optical retardation values may be used to calculate/predict the amount of visible pattern, commonly known as anisotropy or iridescence, present in heat-treated glass.

Glass, in its annealed state, is isotropic, meaning that values are the same no matter what direction they are measured.  In this case, the velocity of light transmission remains constant in any direction.  As soon as stress is introduced, the transmission values begin to differ, dependent on the direction of measure.  Heat treated glass becomes anisotropic.

The study of anisotropy is not new and has always been a point of contention between glass fabricators and purchasing stakeholders.  Some fabricators are better at managing stress induced optical distortion than others.  Even so, variable such as time of year, humidity, glass thickness, tempering oven performance and even operators, among other variables, can change the heat-treated characteristics of glass day-to-day.

The invention, adoption and furthering ubiquity of glass scanners capable of mapping retardation values has opened the door for proper measurement of heat-treated glass optical properties and paved the way for ASTM C1901-21.

“Having a world-wide standard allows fabricators to provide clients with an understanding of how much roller wave they will actually see in their heat-treated glass.   There’s never been a way to provide a measurement, it was really, ‘what you get is what you see,’ and that was the end of the conversation,” says Moreau.  “With this standard, a fabricator can supply an architect, glazier or owner with real results, and they can accept the glass based on real, measured properties.”

AGNORA always puts its best glass forward, and focuses on leading the industry in unparallel quality and professionalism.  Recurrent investments in leading standards, new technology, and new methodology is what sets AGNORA’s fabrication facility apart.  Just as we embrace challenging projects, we embrace challenge within our own organization, with the belief that BIG Glass, means BIG ideas, BIG investments and world-leading systems and procedures.


The ASTM C1901 standard can be purchased here. 

Louis Moreau sitting on one of his glass bench designs