Terry and Shay Weisbrich tucked in Wednesday night feeling grateful and astonished that their Bennett Valley country home was not devoured by a fire ignited by a sunbeam refracted onto the wooden house by the dog's shiny water bowl.
"It's a good thing we got to it in time because there's a pretty good-sized hole burned in the siding," Terry Weisbrich said.
A flabbergasted Bennett Valley Fire Department engineer, Rene Torres, said he and his colleagues had no idea what had charred a small area of the cedar siding on the house off of Pressley and Sonoma Mountain roads — until he noticed an empty chrome bowl on the deck.
Terry Weisbrich said he'd kicked it aside as he rushed to aim a fire extinguisher on the piece of siding that began smoldering sometime before 3 p.m. Wednesday.
Firefighter Torres asked him where the water bowl had been before he moved it. Weisbrich returned the bowl to its original position on the deck.
"It was uncanny," Torres said. In an instant, he said, "There was a dot of concentrated light right in that exact area" of the charred siding.
The Weisbrichs, who are retired, suspect they might have lost the house on a notably hot, dry and breezy May Day had they not been at home when their dog, Toby, a flat-coated retriever, began to bark excitedly.
"This dog does not bark," Terry Weisbrich said.
His wife walked about to investigate what Toby was worked up about. Through a glass door at the rear of the house she noticed what she first thought was steam but quickly realized was smoke.
She shouted to her husband, "We've got a fire!"
Terry Weisbrich dialed 911 and rushed around back to find smoke rising from a small spot of blackened siding. He moved Toby's 9-inch steel water bowl out of his way and let loose with the extinguisher.
Firefighter Torres and his team arrived quickly and removed a bit of siding around the charred area to see if there might be faulty wiring inside. There wasn't.
Then Torres eyed the water bowl. Moments later, with the bowl returned to where it had been, everyone saw the reflected beam of light focus onto the siding.
"It really could have burned that house down," the fire engineer said.
The firefighters left the grateful couple — "I'm going to bake them cookies," Shay Weisbrich said — and Terry Weisbrich got on the phone to alert the bowl's manufacturer to the danger.
"It is probably something they need to warn consumers about," he said.
An Internet check revealed that in Bellevue, Wash., four years ago, homeowners and firefighters suspected that a $200,000-plus fire was started by sunlight focused into a beam as it passed through a dog's water bowl that was partially filled and suspended by a wire stand on a deck.
A Bellevue firefighter recreated the conditions in an experiment and within seconds, sunlight refracted onto a piece of cedar beneath the bowl caused the wood to begin to smoke.
A professor of optics interviewed by ScientificAmerican.com said it was plausible that sunrays focused by a glass water bowl could start a fire, but only under very specific conditions.
The professor said that "if it is going to happen, late spring is the time."