The original method of stained glass, such as the type found in the windows of churches and cathedrals across the UK, is crafted using small pieces of coloured glass.
The colour is achieved by adding a metallic oxide to the glass, while it is in a molten state. This means that with ‘Stained Glass’ the colour pigments or chemicals are an integral part of the glass itself. Cobalt, for example is added to molten glass to create blue glass, and gold is used in some red and pink coloured glasses.
The molten glass is then rolled into thin sheets and cooled, before being cut and arranged into a pattern. A soldering iron is then used to fix the pieces of coloured glass between a metal frame.
Stained glass colours can also be achieved by painting onto the glass and then fusing the colour to the glass using a kiln.
More modern methods of glass painting, particularly for crafting, do not include a firing method to fix the colours. It is simply transparent paint on top of the glass. Scratch this type of stained glass and the coating will be removed to reveal the clear glass underneath.
In terms of durability, the original method of stained glass found in historic buildings will last for centuries. This is because they are composed of real glass, however painted glass is less long lasting and is much more susceptible to weather damage and general wear and tear.
When choosing which type of stained glass to use for your project it is also important to consider repairs. For example, the original form of stained glass will allow you to have any broken pieces removed and replaced, whereas in the case of stained glass paint the design could be completely lost if the window is damaged.