Ok, so this started out as one post but grew so much, it had to become a 3-part series.  The most common questions we hear about our spandrel coatings are:

#1 What is Spandrel?

#2 Can I put Spandrel in a vision area of a building?

#3 Silicone spandrel and frit spandrel are the same thing right?

Those are indeed the top three questions I get about spandrel, the little known part of a glass building that can have the greatest aesthetic impact.

PART I - What Is Spandrel?


span-drel [span-druhl] - noun

  1. Architecture. an area between the extradoses of two adjoining arches
  2. 2. (in a steel-framed building) a panel-like area between the head of a window on one level and the sill of  a window immediately above.

    Meh huh, what?

    The origin of the word spandrel comes from the 1400’s as an architecture term to describe the space between two arches, as in the illustration below.  It’s that arch between the arches, in this photo, where the two women reside.  It’s spanning the distance between the arches and helping to give structural support.

    Courtesy http://danceswithanxiety.blogspot.com/
    Courtesy http://danceswithanxiety.blogspot.com/

    Somewhere along the line of history, architects or the glass industry took the word spandrel and applied to to an all glass building.  If you look at the photo below, you can see where the office area would be and a shorter glass level under that.  This is spandrel and it’s a level of glass that is opaque and colored, which also hides the electrical and mechanical areas between the floors of a building.

    Shaw 1 320

    To opacify the glass, one of several products can or have been used; ceramic enamel, silicone elastomers, urethanes, films, etc.  In fact, when we started ICD, the three big spandrel coatings were ceramic enamel, inexpensive urethanes, and polyester film.  Around 15 years ago, due to many performance and cost issues, polyester films suddenly ceased being used.  The hole left from that was filled by the two next most popular coatings, ceramic enamel and silicone (or more specifically OPACI-COAT-300).

    Ceramic enamel is a very viable way to opacify glass and has had a very long history in doing so.  The product is a coating that used to be sprayed on glass (and still can be in some areas), but today is roller coated or screen printed, run through a drying oven (flashing off volatiles) and then run through a tempering oven.  In which the coating is fused to the glass and the glass is heat treated at the same time.  To do this, the components of the coating have to withstand very high temperatures (such as heavy metals, organic pigments that have carbon in them will burn up and those temperatures).  Great advancements have been made in the last few years to help make enamel more green but it still suffers due to having to use temperature resistant components.

    Fast forward to today and we have ceramic enamel, silicone and to a smaller extent urethanes, acrylics and panel systems.  There are some big differences between the two most used products; enamel and silicone.

    So, to sum up what “spandrel” is to a building, it’s the opaque and colored section of glass between the office floors in an all glass clad building, often hiding the mechanical components of the building.  I should add one more bit, due to the increases in high transmittance and high reflectance glasses today, architects can now use the spandrel cavity as either color accent or pick colors for the glass to harmonize with the vision glass.  Neato!

    I've also heard that it's a military missile as well. =\

    To Be Continued with PART II "Can I put Spandrel in a Vision Area?"