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Old and new technology were part of a recent preservation and update project to preserve prisms and install a new light source in the Grosse Point Lighthouse optics mechanism. Along with repairs and thorough cleaning, the lighthouse optics mechanism prism seals were restored. Litharge, a type of caulking used a great deal during the 1800s, was reapplied to secure glass prisms in their brass frame. Also, a new Coast Guard-recommended LED flashing unit was installed, replacing the old mechanism which used incandescent light bulbs. The light is listed as a private, as opposed to government-operated, aid to navigation by the Coast Guard, with a nominal visible range of 12 miles in good atmospheric conditions.
Donald Terras, Director of the Lighthouse Park District, said “I hope people will have a renewed appreciation for the preservation of the historic lens, which we are watching over . . . Ongoing use of the lighthouse as a private aid to navigation is a priority, and the Lighthouse and its Fresnel [pronounced fray-NEL] lens are a unique piece of technological history that should be preserved in situ, which we have done.”
The recent preservation work was carried out by Kurt Fosburg, a licensed ship captain, a lighthouse lampist and the owner of Superior Lighthouse Restoration. Capt. Fosburg is one of a small number of professionals certified by the U.S. Coast Guard to maintain the Fresnel lenses.
Asked how he felt about the change from incandescent to LED light in the lens, Mr. Terras said, “I thought it was a good idea to follow the lead of the Coast Guard. From a strictly aesthetic point of view, it doesn’t have the draw that an incandescent light has . . . But, I don’t romanticize too much about it, I don’t get really emotional about it. I’m a pragmatic guy. [The new light source] is a lot cheaper and will last a lot longer.”
Capt. Fosburg, who has worked to preserve such lenses for 18 years, said that the Grosse Point second order Fresnel lens is in great condition. There are six sizes of Fresnel lighthouse lenses, divided into “orders” based on their size and focal length. In modern use, these are classified as first through sixth order. A second-order lens, like the one at the Lighthouse, has a focal length of 750mm (29.5 inches) and a maximum diameter 2.069 meters (6.8 feet) high.
The Fresnel lens was invented in 1822 by French physicist, Augustin Fresnel. The Grosse Point Lighthouse’s Fresnel lens was built in Paris in 1850 by craftsman Henri Lepaut and is the largest and last of its size left in use on the Great Lakes. It has a barrel-shaped design and is made up of multiple glass prisms that capture and intensify light coming from a single source in its interior. A thorough, professional cleaning of the lens after this procedure “should last for several years with only minimal routine dusting required,” said Capt. Fosburg.
Grosse Point Lighthouse was built in 1873 and operated by the federal government as the lead navigational aid into the Port of Chicago until it was de-staffed in 1935. Since then, stewardship of the original 1873 structure has been overseen by the Lighthouse Park District of Evanston. Mr. Terras has been the director at the Lighthouse for more than 35 years.
“I can’t tell you how many phone calls I get from people asking if this place is haunted . . . It’s always on people’s minds,” said Mr. Terras. “The Ghost Hunters wanted to do an episode here and I said it was fine, but I’ve lived here a long time and my standard line is that the only person haunting this place is me.”
The Lighthouse is one of only 12 lighthouses in the U.S. to be designated a national historic landmark, a designation which Mr. Terras worked for a number of years to obtain. He achieved success in 1999. The Lighthouse is one of only three national historic landmarks in Evanston, along with the Dawes House and the Frances Willard House.