This will be messy, so do it over newspaper and don't wear good clothes! To make the background: mix 1 teaspoon of liquid dish soap, 1 teaspoon of sugar and 1/2 cup of waterin a small mug or bowl. Stir them with a straw, then blow bubbles up to the top of your mug. I kept blowing for awhile so they were running over the side to make sure there were plenty. Then carefully add a few drops ofre-inker to your bubbles. Touch your cardstock to the bubbles so that they pop, the ink will stick to your cardstock in an interesting pattern. You will probably need to reblow the bubbles a few times to get the effect you want. Experiment with it, this was my second try. I used Real Red ink which made a really pretty, delicate pink background - not really appropriate for a little boy's birthday card.
I still need to come up with a fantabulous idea for cards for a few daughters' birthdays, think I'll look for some more reinker techniques. Stay tuned!