This Glass Technical Paper (GTP) is intended to provide guidelines that apply to the appearance of vision and spandrel insulating glass unit (IGU) edges at the time of fabrication. The appearance of the IGU edge is a function of the materials and the fabrication process.

This GTP is not intended to address changes to the IGU edge appearance that may occur over time after fabrication, including, but not limited to, effects due to glazing system design, shipping, handling, storage conditions or installation.

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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 2011. This version of the document was updated and published in February 2025.