A feather and a sponge can be your best friends in creating specialty paint effects. A good, stiff turkey feather is ideal, although in a real pinch, you can steal a few from a feather duster. Purchase a sea sponge from a paint, hardware or bed-and-bath store (they're not cheap, but they are reuseable: make sure you rinse your sponge out well when you're done, and you'll be able to use it over and over). Choose a large sponge that has a lot of rough edges and texturing to it.

This effect works nicely on architectural elements - we've used it on platforms, recessed bars, countertops, step risers, and a tub surround (for the play Bathroom Humor).

Decide what colors you want your marble to include. Three is the minimum for the best effect - a dark, a medium, and a light - but you can use more if you like. (One of my favorite combinations for green marble is jade green for the medium, dark green and flat black for the dark, and a very light sea-green for the light.) Find a piece of real marble, or gather some color photos to study the play of colors and veining.

Gather the following materials: coffee cans or margarine containers for mixing (one for each color plus an extra), roller or brush for applying a base coat, a bucket of water, feather, sponge, rubber gloves, and your marble sample.

Using a brush or roller, lay a base coat of the medium color on the object you want to marbleize. Pour out a little of your dark, medium and light colors into separate containers and add a little water to each. Now's a good time to pull on your gloves.

Wet your sponge first in the bucket of water (and keep rinsing it out periodically as you work to keep it damp), then using the dark paint, begin daubing it on over the base coat (this works best if your base coat is still a little wet, although that's not necessary). Rotate your sponge and vary both the amount of paint on the sponge and the pressure as you apply it to avoid a repetitive pattern. Vary the colors by dipping your sponge in the medium and or light colors, then back into the dark, and vice versa, to create a mottled pattern - don't worry about keeping the colors in your containers pure; the random mixing is OK. And feel free to go back over areas that you've already painted - this adds depth. You may want to occasionally press down harder and lay down a swath of color using a scrawling motion that mimics the pattern of real marble (keep your marble model or photo close at hand to study as you go).

When you're satified with the mottling, it's time to do the veining. Pour out a fresh batch of the light color into a small container (you won't need much) and add enough water so that it's smooth and spreadable but not drippy. Dip your feather in the light color, then pull it across the lip of the container to remove any excess. Study the mottled surface of the object you're marbling to decide which direction the veining would logically go (you might want to follow some of those scrawling swaths that you created), and then lightly draw the tip of the feather in a wavy line across it, twirling it just a bit as you go to vary the width of the line, and tapering it off lightly at the end. Continue like this, varying the length, width and direction of your lines, and making appropriate forks and splits in the veining (again, keep your marble sample handy for reference). Vary the color of the veining by occasionally dipping the feather into the medium or dark and then into the light. Know when to stop - too much veining will look unnatural.

Finish off the marbling effect by VERY lightly sponging on some of the light, dark and medium paints in random spots, barely touching the sponge to the surface, again rotating your sponge to vary the pattern (spattering, by hitting a wet brush to produce fine paint droplets also works, although you may not have as much control as you do with the sponge). Make sure some of these light touches are applied over the veining so it doesn't jump out from the rest.

EXTRA TIP: If your marbled piece is in a spot on the stage where glare from the lights is not going to be a problem, you can give it a shiny glaze by applying a mixture of white glue (Elmer's) and water when it's dry - mix in water until the glue has a runny enough consistency to spread easily with a brush. This technique works for any painted surface that you want to have a shine to it - it's especially good for floors, as it adds a light protective coat.

The books Recipes For Surfaces, Volumes I and II by Mindy Drucker and Nancy Rosen, contain excellent step-by-step instructions for a lot of different natural paint effects, as well as a lot of photos of the real thing to give you something to go by.