Frenchman lit the world's coasts
| • | The lighthouses of Hawai'i |
| • | Profiles, from Kaua'i to the Big Island |
By Chris Oliver
Advertiser Staff Writer
In 1822, Augustin Fresnel, a French physicist, invented a lens that would make his name commonplace along the seacoasts of North America and Europe.
The lens looked like a giant beehive, with a light in the center. The lens could be as much as 12 feet tall, its structure made from glass rings above and below to bend the light into a narrow beam. At the center the glass was shaped like a magnifying glass, so the concentrated beam was even more powerful.
Tests showed that while an open flame lost almost 97 percent of its light, the Fresnel lens was able to capture all but 17 percent of the light. This enabled the lens to throw light 20 miles and more to the horizon.
In the past, Fresnel lenses were constantly maintained by the U.S. Lighthouse Service, said Gretchen Voeks, a conservator with the National Park Service.
"Lighthouse keepers polished the lenses and the bronze panels on a regular basis ... a very time-consuming procedure and abandoned by most keepers after the U.S. Coast Guard automated the lights," she said.
Voeks, who is looking at ways to remove corrosion from the bronze panels that stabilize the lens and preserve their oxidized surfaces, in September visited lighthouses at Kilauea and Kalaupapa. The lens for the latter is now crated and in storage.
"The National Park Service is discussing the idea of restoring and exhibiting the Kalaupapa lens," Voeks said.
"The challenges of maintaining Fresnel lenses come down to a lack of funding and lack of knowledgeable caretakers. After the lens is conserved there must be a commitment to regular maintenance."
Voeks said the Fresnel lens at the Diamond Head lighthouse appeared so well cared for that it was useful for comparison with other lenses she was working on.
Because of the growing interest in lighthouses and maritime history — and the transfer of the care of lighthouses from the Coast Guard to other caretakers — the conservator finds herself in growing demand.
"I love what I do," Voeks said. "It's great to be able to work with such fabulous feats of engineering ... and you can't beat the view."
