I thought originally that this was a spoof or April Fool's Day hoax but it seems to be real! Very cool!!
"How hot does your 3D printer’s hot end get? Most low cost printers heat up to 240°C (464°F) at the most because they contain PEEK which starts to get soft if you go much higher. Even a metal hot end with active cooling usually won’t go much higher than 400°C (752°F). Pretty hot, right? MIT's new G3DP printer goes to 1900°F (over 1000°C) and prints optically clear glass.
By changing design and print parameters, G3DP can limit or control light transmission, reflection and refraction. The printer uses a dual heated chamber. The upper chamber acts as a 1900°F kiln while the lower chamber serves to anneal the structures. The print head is an alumina-zircon-silica nozzle.
There’s a patent filed on the process, apparently, and you can read the technical details in this thesis
and in some upcoming publications"
Apparently you could use Spectrum 96 or Bullseye 90 nuggets as the glass source so maybe one day....when the G3DP printer is less than $10,000!