Old window glass imperfections

[wycombeite]

Does anyone know the name for the imperfections in old window glass that makes the view through it distorted?

[jake-the-peg]

Don't know if there's a particular term but old glass was blown as a large disk and cut from that. The "bulls eye" at the center which is now often seen in feature windows was often waste or sold very cheaply.

Later glass was formed from a cylinder and opened out.

Both methods create more imperfections than modern glass which is extruded onto a molten tin bath.

It can still be bought as restoration glass from people like Hetleys

http://www.hetleys.co.uk/rightcata.html

More information here:

http://www.buildingconservation.com/articles/glazing/glazing.htm