There are many ways to get interesting patterns in your clay. Look around your house, your yard, and your kitchen, and you will start to see all kinds of things that can make good textures. Rocks, the bottom of your shoe, the wheel of a toy truck, a meat tenderizer, a piece of driftwood. The list is infinite. But here are a few additional ways to make more complex patterns. Lastly, there are various manufacturers that have off the shelf texture mats, rollers or stamps.
See how to create surface texture using the potter's wheel
1. Bisque rods. Make a bunch of coils of clay. For example, a good size is 1" diameter and 8" long. The main problem with bigger diameters is the time it takes for the clay to dry before firing. But you can sit these aside and let them dry for a good long time. While the clay is still soft, carve or press patterns into it. For example, poke the end of a needle tool in to make holes. Or press the edge of a ruler in to make lines. Cover the whole surface with your pattern. After drying, bisque fire the pieces. Now you can use these rods to make patterns in wet clay. Simply roll your rod across the clay, pressing while you roll, and you can make long, continuous patterns.
2. Take wood dowels and apply patterns to them with hot glue. When the glue dries, the dowels can be rolled across the clay to make similar patterns.
3. Wrap string, twine or rope around a dowel in straight or criss cross patterns. Roll over the clay.
4. Carved Linoleum. I got this idea from a potter who used to be a print maker. Linoleum was used for flooring before we had the vinyl floors of today. Linoleum is a mixture of linseed oil and cork. When heated it becomes soft so you can carve into it. Then it hardens when it dries. You can get linoleum at art supply stores. At the same time, you can buy a set of Speedball linoleum carving tools for about $7. Either draw or trace a pattern on the linoleum, then carve it out with the tools. You can use very intricate designs, such as a tree with many branches and leaves. The textures transfer very nicely to the clay.
5) Using off the shelf slab mats or texture molds
To transfer the pattern to a slab, put the pattern on the clay and press with your hands or a roller.
You can transfer the pattern to a cylinder as well. This is very cool for putting texture on thrown and altered forms. The cylinder should be stiff enough that it doesn't collapse, but soft enough to take the pattern of the clay. Place the carved piece of linoleum face up on a table, hold the cylinder sideways, and slowly roll the cylinder across the pattern. While you are rolling it across, use a smaller roller inside the cylinder, to press the side of the clay cylinder into the linoleum. The mini-roller works really well for this, or the pony roller for larger areas. They can be found on this page. http://www.bigceramicstore.com/Supplies/HandbuildingTools.htm
*** Important note: Non-porous surfaces, such as plastic, metal, etc. will stick to wet clay. This can make it difficult to get clear patterns. Therefore, the best materials for impressing are porous materials such as wood, bisque clay, and plaster. If you are using a non-porous object, try putting a thin piece of cloth between it and the clay, or a piece of Saran wrap. We at Lakeside Pottery, use W-D40 sprayed on non porous texture tools.