Several of the tints are very bright, but have now been superseded for convenience of usage by various synthetic dyes.
The process employed is to wash the thread thoroughly in urine long kept ("fual"), rinse and wash in pure water, then put into the boiling pot of dye which is kept boiling hot on the fire.
The thread is lifted now and again on the end of a stick, and again plunged in until it is all thoroughly dyed.
Amateurs may wish to experiment with some of the suggestions, as urine (human or animal) is used in many recipes as a mordant.
This article incorporates text from Dwelly's [Scottish] Gaelic Dictionary (1911).