You'll see the hot furnaces where the glass mixture (the batch) is melted and blown, and you'll watch the cutting that is done by hand and eye as well as the polishing or engraving.
The hot furnaces are over 1000 degrees at all times.  
mnli hypothesis: The hot furnaces are over 1000 degrees at all times.   premise: You'll see the hot furnaces where the glass mixture (the batch) is melted and blown, and you'll watch the cutting that is done by hand and eye as well as the polishing or engraving.