.............
org20 Dyes, dyeing, separation of black felt-tip pen ink

What you need: Black felt-tip pen STABILO point 88 fine 0.4,  plastic strip coated with silicagel, 5-ml injection bottle with a wide mouth, dropper bottle with methylated spirit.
* Left: Cut a pastic strip that fits to the mouth of the bottle. Make two dots  on the silicagel with the pen: side by side and 5 mm above the lower end of the strip.
* Photo 2: Transfer 10 drops of methylated spirit into the bottle. Carefully place the strip into the liquid.
Observations Photo 2, 3: The blue colour is separated into yellow, violet and blue dyes by the ascending spirit.
* Right:  The strip was dried. The silicagel with the yellow, violet and blue colours can be removed separately.
Explanations The black colour of the pen was attracted by the silicagel. The spirit was lifted upwards through the silicagel by capillary forces (similar to ink in a blotting paper). The black colour proved to be a mixture of three different dyes. Each of them is bonded  by the silicagel with in a specific force and each of them is dissolved differently by the spirit while it moves upwards through the silicagel.
So the three dyes moved upwards with different speeds resulting in their separation.