NGA FB57-24 PDF

The glass industry has been challenged for many years with creating an optical measurement standard for glass products and windows. Measuring glass distortion, i.e., deviation from flatness, is not a new topic. However, with tighter energy efficiency demands, more variations in glass sizes, code changes and new glazing systems have resulted in more heat-treated glass, double (and even triple) insulating glass units, and multi-ply laminates in use than ever before. All of these products may increase the amount of distortion seen on buildings. Learn more about creating an optical standard and/or number for a glass product. The Technical Services Division of the National Glass Association (NGA) has produced this Glass Technical Paper solely for informational purposes. This Paper was developed by dedicated member volunteers and subject matter experts. The original version of this document was published in 2018. This version of the document was updated and published in June 2024.