Geoffrey Baer visits the John Hancock’s Crown of Lights to find out how the Hancock Building makes its seasonal lighting wardrobe changes in this week’s editionof Ask Geoffrey.He also sheds light on the infamous shadow casting sculpture in Hyde Park and explains why some city roads have both a street and a place.

How long does it take to change the lights at the top of the John Hancock Building? It seems to take a several days. What is involved in changing the lights from one color to another?

Trish Holland,West Loop

One of the Hancock Building’s most recognizable features is what’s called the Crown of Light at its very top. The crown was originally white all year round, but in recent years the color of the crown has been changed from time to time to celebrate holidays, seasons, support charities and of course, wear the colors of Chicago sports teams.

The Crown of Lights is comprised of 552 eight-foot-tall fluorescent tubes mounted in cabinets up against the windows that ring the 99thfloor. The color changing process is pretty simple – building engineers climb to a 99thfloor catwalk, remove the flourescent tubes, slip them inside colored plastic sleeves, and replace them.

Changing the color of all 552 tubes takes some time – about 40 hours for two building engineers. It’s all done from inside the building, so there’s no danger of falling, but changing the color in the summertime does pose an occupational hazard. Hancock Chief Engineer Bill Casey told us moths are attracted to the lights, which in turn attracts large numbers of large spiders. Workers in the summer have to wear long pants and shirts with their sleeves and cuffs duct-taped closed. They even wear hoodies to keep spiders from going down their backs.

Casey brought us up to see how his crew does a color change. Because it’s April, the lights were switched to blue to support Autism Awareness month. Building management is hopeful that someday the fluorescent tubes can be replaced with LED fixtures that can be controlled remotely via computer, but for now, it’s handled the analog way.

Below, a slideshow showing the progression of the Hancock Building