1. Put a quarter-size glob of oil paint into a glass jar or can. Add enough white spirit or turpentine so that, when mixed, the paint has the consistency of milk. For mixing, we used sticks we found outside, but popsicle sticks would be perfect for this.
2. Now to create the "size" (the thickened water that the paint will float in). We used CMC (Carbon Methyl Cellulose) pH neutral adhesive. Use about 1 - 2 tablespoons of CMC to 1 litre of warm water (or 4-8 tablespoons per gallon). Mix well initially and then let stand to continue dissolving. Mix occasionally. It should be thick but still pourable. Dilute with a little water if it thickens too much. When ready add in batches to warm water in marbling tray to gain a marbling solution that will float the paint. Too thick and the paint will not spread around - too thin and the paint will fall to the bottom. (A simple test is to run your hand through the water and you should encounter some resistance)
We only prepared the size a few minutes before we begain marbling, so it didn't have time to thicken enough. I would recommend preparing the size at least half an hour in advance. To solve our problem, my resourceful mother plucked a leaf off a nearby aloe plant and we added its gel to the water.
It got messy (in a good way!) very quickly. The crumpled newspaper in the back was used to soak up excess paint to start a new design:
3. Droplets of paint were added to the water and then mixed with sticks to make patterns:
4. Lay down the paper slowly, starting in the center. We tried a few different types of paper and found the wallpaper (shown here) to be a little thick.
5. Ta-da! Let the excess water drip off and then rinse the paper with water. We did this by laying out an old window in the yard, laying the paper on top, and briefly running it over with a hose.
6. Hang your work out to try - and you're done!
A closeup:
Some of the papers I took home with me on the plane. Thankfully they survived the trip to New York:
There are a number of different techniques for marbling, including kid-friendly versions.