One of the workshops I did while I was at Bicheno was on creating an opalescence yarn. It was inspired by an article by Stephenie Gaustad and is about light and colour effects within a yarn. This is created by carding ( over and over a range of white and coloured fleece, silk or mohair together. The base is about 95% white yarn with no yellow undertones then a blue/black is added to get a light grey. This gives you the opal milky base. To this is added the sparks and embers in a combination of hot pink, magenta, turquoise, aqua, purple violet and neon gree( I didnt use this). These are added in tiny whisps of colour.