If you've purchased treated wood directly from a lumber mill, chances are the lumber mill has stamped the wood in ink. These ink stamps help indicate where the wood came from, how to wood was treated, its grade and the type of wood it is. You will want to remove the ink directly from the wood if you're not covering it up with paint. A variety of products will do this, but you can save money by using home products and methods.
Slightly dampen a clean cloth in paint thinner.
Press the cloth over the ink stamp to soak the wood. This will help loosen the ink stain.
Remove the cloth and gently sand the surface of the wood with fine-grit sandpaper. Sand in the direction of the grain to avoid splitting the wood.
Gently sand the wood with medium-grit sandpaper, if the ink stamp is still visible.
Wipe away the sawdust.