Furnace to melt glass of Beth She'arim slab was 1700°C.
The pipes shown in the image are modern, not ancient.
Photo shows Dr. Robert Brill obtaining a sample of the limestone bottom of the tank in which the glass was melted. The knife, shown, was used to scrape a sample off of an area nicknamed "millipede alley," because there were so many insects on it.
Title supplied by Robert H. Brill.
Reference list A : Glass studies, in: Brill, Robert H. Chemical analyses of early glasses, A-13
Reference list A : Glass studies, in: Brill, Robert H. Chemical analyses of early glasses, A-17
Digitized from a slide by Boston Photo Imaging; Corning Museum of Glass; 2011.