The furnace, heated to 1,500 degrees Celsius, was glowing red. Workers at the Arc International glass factory loaded it with sand that slowly pooled into a molten mass. Nearby on the factory floor, machines transformed the shapeless liquid with a blast of hot air into thousands of delicate wine glasses, destined for sale to restaurants and homes worldwide.Nicholas Hodler, the chief executive, surveyed the assembly line, shimmering blue with natural gas flames. For years, Arc had been powered by cheap energy that helped turn the company into the world’s largest producer of glass tableware — and a vital employer in this working-class region of northern France.But the impact of Russia’s abrupt cutoff of gas to Europe has doused the business with new risks. Energy prices have climbed so fast that Mr. Hodler has had to rewrite business forecasts six times in two months. …
