We had great fun making these using polystyrene eggs and some old plastic eggs, that I had kept from a few years ago.
I used an old plastic tray that I don’t want, and put in some cold water. Put about 4 drops of marble ink onto the water and swirl it round with a cocktail stick. I pushed the cocktail stick through the Middle of the egg and made it like a lollipop for the children to easily dip in the water without getting messy fingers.
Such a beautiful effect and so simple to do. Great on a rainy day.
I would love to see what you have managed to do.