spot colour

In more detail

The ordinary way of printing a colour is to build it out of the four usual inks, laid over one another in the right amounts. It reaches nearly every colour, and nearly is the word: a firm's own red comes back a little different from one press to the next, and different again on a rougher paper.

A spot colour is mixed in a tin before it ever reaches the press, to a recipe the whole trade shares. It goes down in one pass, so the colour is exactly the colour, on every run and on every paper. A letterhead in two of them also costs less to print than a job in four, because the press carries two plates instead of four.

What it does on a real document

The file names the ink and says how much of it goes down, as a single figure from nothing to full strength. Beside that it carries a stand-in built from the ordinary inks, so the page can still be shown on a screen or run on a press that does not hold the tin.

Naming the ink is what puts those marks on a plate of their own. Where a document merely draws the colour, somebody at the printing works has to decide what was meant, and the day their answer differs from yours the job comes back.

Where it comes from, and why

Printing one flat colour from one tin is older than colour photography. What is newer is the shared recipe book: a numbered range anybody can order by number, so a designer in one country and a press in another mean the same colour by the same word.

See it on a finished document

Inks on plates of their own Several plates at once, each at its own strength The rules behind this word, and the texts they are read from