The Glassworker is a machine added by Extra Trees. It can be used to form a block of stained glass with different color patterns. It is functionally similar to the Woodworker.
The Glassworker requires 2 blocks of Stained Glass or Pigmented Glass (Botany) and Glass Fittings (Extra Trees) as an adhesive (or Wood Polish (Extra Trees) for older versions). The stained glass goes into the top slots of the machine (order matters) and the adhesive on the bottom. Patterns can be previewed by clicking on them. The menu can be scrolled through and filtered by name by entering text on the bottom-right.