National Geographic : 1943 Jan
Slow-cooling Is as Vital to Glass Making as Is Quick-freezing to FoodPreservation Candlesticks, goblets, and vases come off the presses at 900 degrees. They pass through a heated tunnel called a lehrfortwo tofivehours tocool them down to room temperature. Such annealing reduces the strains which cause breakage. Photograph made at Fostoria Glass Company, Moundsville, West Virginia.