What is tartan? What makes it unique?
A tartan (or ‘plaid’) is a simple criss-cross coloured pattern, which is normally woven. Each tartan is defined by its “sett“, a sequence of coloured lines called its “thread count“.
A tartan’s thread count is normally (but not always) mirrored… i.e. 12 yellow, 16 red, 10 blue - 10 blue, 16 red, 12 yellow. And the same sequence is usually (but not always) woven both horizontally and vertically to produce the distinctive check pattern.
This simple principle allows literally millions of possible designs. Each design is unique, and can in principle be legally copyright. This is defined by its thread count. But since colour shades are involved, where one design becomes distinct from another is a matter of expert judgement with no absolute rules. This is usually arbitrated by bodies such as the Scottish Tartans Authority.
Each sett is traditionally given a name, associating it with a clan, family, organisation, locality, or other body. Bodies can have more than one tartan, due to historical variations or different uses.
It is important to understand that it is the sett (defined by its thread count) that defines a particular tartan. Any sett can be woven in a variety of colourways (e.g. ancient or modern shades) which are open to interpretation by different weavers.
A tartan can also be woven in different materials with their own characteristic sizes and colours. For example, the ’same’ tartan will have a much smaller pattern and brighter colours when woven in silk than when produced in heavy weight wool.