The palette of materials that can be used as 3-D printing “ink” is quickly growing in diversity, but one ubiquitous material has, until now, been absent: transparent glass.

It’s already possible to use tiny granules of glass in a powder bed with conventional 3-D printing techniques like jetting and sintering, but the products turn out opaque. Now researchers at MIT have demonstrated the first-ever machine that can print molten glass through a nozzle and make transparent glass objects layer by layer according to digital instructions.

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