Mosaic artists cover an infinite variety of surfaces with mosaic tile or glass. Some are large and durable enough to become outdoor sculptures; others are small, like paperweights or ornaments. Anything can be covered with mosaic if its surface can be made rigid enough to hold the tile and grout without cracking. The easiest 3-D mosaic to start with is a pre-existing form, and there are many of these to choose from. Your local craft store sells an assortment of Styrofoam objects such as balls and eggs, and any garden ornament, such as a concrete bird or a terracotta pot, can be covered in mosaic as well. Start with a simple object, such as a Styrofoam ball, to create a unique ornament for the holidays.
For this project you will need a Styrofoam ball at least a few inches in diameter (the larger it is, the easer the project), a permanent marker, tile or glass pieces (the smaller the better, in order to fit on the round surface), white glue (Weldbond is the mosaicist's choice), nonsanded grout, pieces of heavy cardboard, disposable gloves, paper towels, and clean rags. For small round objects like this, I prefer to use the 3/8-inch tiles, which do not have sharp edges and come in all colors — even metallic! The website Mosaic Basics offers a wide assortment.
If you wish to keep the Styrofoam ball from rolling around while you work, you can set it on a clean cat food can from which you've removed both the top and bottom lids. After your first one, however, you'll have acquired the knack of holding it with one hand while you apply tiles with the other!
Draw your intended design on the ball with a permanent marker. If you're trying for a symmetrical design, you may wish to draw it out first on a piece of paper, then transfer it to the ball.
Start attaching tiles with the glue. For best results, dab a small amount — about 1/8 to 1/4 teaspoon — of glue on the ball and press the tile onto it. Press firmly, and hold about 5 to 10 seconds to make sure it will adhere. Continue until your design is finished. The Weldbond glue sets quickly, so you will usually be able to tile the bottom half within an hour of tiling the top half. When the ball is covered, let it sit for several hours or overnight.
Mix up a small amount of grout according to package directions. Using small pieces of heavy cardboard (you'll need several, as they get wet and unusable quickly), spread the grout into all the crevices around the ball. Wear disposable gloves while you do this, because there is no way to grout completely without getting it on your hands. Let the ball sit for about half an hour, then carefully wipe off the excess grout with paper towels, taking care not to dig out the grout from between the tile pieces. After another hour or so of dry time, buff any grout haze off the piece with clean rags.
To prepare to use as a hanging ornament, push a T-pin (available at sewing retailers) through the wet grout and almost all the way into the Styrofoam ball; leave it sticking out about ¼ inch. Once the grout dries, the pin will be held fast, and you can tie a ribbon around it.