Marbling has three main parts: size, marbling paints, and paper. The size is the liquid used to float the paints on. The liquid does not have to be overly dense. The first time I marbled I created a mixture of gelitin and water to create a size (I wouldn't recomend it since the gelitin needs to remain cool to stay the right consistency; it is also difficult to remove the sticky gelitin from the marbled paper) but this time I found that purchasing powdered carageenen from your local artists supply store works best. The preperation envolves adding three cups of warm water to a blender with one tablespoon of carageenen and blenderize until well mixed. Pour the mixture into a prepared waterproof tub. Repeat. Add eight more cups of warm water to the tub and mix all together well (The depth of your size should be between 1-1.5 inches- more is just a waste). Let the mixture rest for 12 hours (putting a plastic sheet over it to reduce evaporation).
Meanwhile you can prepare the paints. While the size is thicker than plain water, care must be taken to ensure your paints are not too heavy (so they won't sink to the bottom of the size). One type of paint that works well (and is inexpensive) is artist acrylic (no gloss, they will sink). For the containers I like 5oz Solo cups. Fill your containers with your colors (1-2 tablespoons works well) and add an equal amount of water (distilled or filtered). Then add one drop of ox gall to each color (this helps to spread evenly and smoothly across the size and reduces sinking of colors).
To distribute the colored dots on the size, it works best to create small whisks. For mine, I first trimmed my broom. Then I trimmed the broom straw to 3 or 4 inches. Bunching the straw at one end, you can wrap twine or rubber bands to secure the straw. Create one wisk per color.
Now you are ready to marble. Uncover your tray of size and stir your colors up well with the wisks. Take you first color out (this will likely be the veins of the pattern you create) and holding the wisk with one hand- tap it with you index finger. Repeat with all the colors you want to use - note that you have complete control over the size of the droplets (if they are too large at first then tap the wisk in your color container first - the drops will tend to start large and tapper down). Once you like the distribution of your paints, you have the option of using a stylus (toothpicks work well) and swirling patterns in the ink. Remember that all of the ink is on the surface so you only have to dip the stylus a small amount into the size.
When you have the pattern you want, take a piece of paper and gently lay it on the size; starting by laying one end of one corner of the paper towards the other works well. Do not drag the paper across the size, it will distort your pattern. (I have read that it is better to prepare your paper (so the colors will adhear better) with 1 tbsp of alum to 1 gallon of water - sponging the solution onto the paper evenly and letting it dry - but since I am allergic I skip this step with no ill results) Once you have your paper on top of the size, grab the edges and place on a flat water proof surface. Now gently sprinkle water on the paper to remove excess carageenen. Then lay your paper out to dry (by a fan on low works well), it should be dry over night or sooner.
Note that after you remove the first paper from the colors there are still colors left on the size- even if they appear faint they will make nice stationary.
More info on marbling can be found at these sites:
http://www.dharmatrading.com/autogen/brochures/html/13/
http://www.earthguild.com/products/dyes/marble.htm
http://members.aol.com/marbling/marbling/
http://members.nccw.net/marble/
These are just a bit of notes and tidbits that I picked up while experimenting with some fun crafts with my friends. Good luck with projects of your own!
