A somewhat overdue correction…in Chapter 5 of Chicago Skyscrapers, I cited a contemporary source stating that the Reliance Building’s skin was “nearly 90 percent glass.” Sharp-eyed CAF docent Chuck McLaughlin sent me the attached photo along with a guess that the actual percentage was more like 75%.
The Reliance’s windows are about 9′ in height. Its terra cotta spandrels are 4’-6” deep (from Freitag’s 1904 book–which gives a total floor to floor height of 13’-6”). So the total glass-to-solid ratio is 66% not counting the vertical mullions. This sounds too low, but I think it’s right if you count the horizontal sills at the base and top of each window as solid.
From the inside, of course, 9’ windows with a 2’-0” upstand for the spandrel (again, from the detail published in Freitag) still gives only 81%, which is “nearly” 90% only in the language of the era’s breathless newspaper editing. I suspect this is where the claim may have come from, and the “70%” claim for the Fisher is, likely, based again on its interior dimensions.
Thanks to Chuck for sending this in–I think it’s critical to get details like this one correct, and as and when a second edition comes out (fondest hopes…) I’ll make sure this gets fixed…