It probably looks fine from the outside

And the answer would be a resounding no.

The second most popular question, which is also the number one issue with spandrel glass in the field next to incompatible components in the cavity, is if a spandrel can be used in a vision area.  No, spandrel glass can not be used in a vision area, be it enamel or silicone or anything.  All coatings have small perfections like craters and pinholes.  To ensure these flaws don’t appear, the cost of applying the coating goes up.  Due to needing clean rooms and more precise coating equipment.

Bottom-line is, all spandrel glass will have pinholes and light/dark spots from the application, yet there are ASTM and GANA standards that show the acceptable limits of these features. If you place these glass panels in a vision area, where someone would be behind the glass looking outside (meaning light behind the glass), they will look very poor.  These types of glass are not meant to be used with light behind them, the were never created this way and will never be.  But if you want an opaque glass in a vision area, just telling the fabricator will reduce your headache when the glass looks like the milky-way.  Several practices can be employed to reduce or remove the pinholes and light/dark area.  Of course, cost goes up.

Need some docs on how to view spandrel glass for quality, once installed?  Check these out:

ASTM C1048 - 04 Standard Specification for Heat-Treated Flat Glass - Kind HS, Kind FT Coated and Uncoated Glass

GANA Glazing Manual

So, remember, keep spandrel glass out of the vision area, it’s not intended for this use.

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