NGA FB18-08 (2023) PDF

As a result of heat-treating glass, optical distortions may arise from out-of-plane deformations of the glass surface. Currently, there are no industry-wide standards that specify acceptable values for these optical distortions; however, there are existing methods/instruments to measure them. The methods/instruments referenced in this document are designed and intended for in-plant use only. These methods for measuring distortion cannot be applied in the field on vertical glazing and cannot be used on insulating glass units. The original version of this document was published in 2008. This version of the document was updated and published in June 2023.