Harbour as part of the pot furnace:
A heat-resistant ceramic vessel in which the mixture is melted and where the molten glass is taken out for the creation with the blowpipe. Capacity of a harbour: 120 - 600 kg
Hard glass: A special glass which is hardly meltable.
Hidden defects or glass defects:
Mistakes which are not immediately recognizable, but appear and become visible primary later.
All glass forms where a more or less strong wall surrounded a hollow space (Examples: drinking glasses, bottles and vases).
An acid which immediately and intensely affects glass. It is an indispensable tool for etching decorations for glass.