Add water to an old plastic container. This project will ruin your container so be sure to use an old one. You will also want to protect your surface with cardboard and/or newspaper. Put on your gloves and start spraying small amounts of spray paint directly onto the water's surface.
Repeat for as many colors as you like. You will start to see a marbled effect on the top of the water.
When you are happy with the look of your paint on the water, dip in your project. I only did the bottom of these vases but you can do as much or as little as you would like. To remove the vase from the water, you may have to push away the excess paint that is still floating. Do this with a craft stick or scrap piece of wood. Then pull the vase out of the water.
Set the pieces aside to dry. I like to dry mine upside down. Repeat for as many pieces as you will be marbling.