Cedar, a naturally beautiful and insect-resistant wood, is perfect for many outdoor applications like siding, decks, picnic tables and outdoor furniture. Because of its natural tannins, cedar does not need to be stained. With age, cedar will turn any range of amber, reddish or darker brown. With so little resin (or pitch) in cedar, it accepts stains and paints of all sorts. Cedar's unique aroma comes from naturally occurring thujaplicins in its heartwood that resist moisture, repel decay-causing fungi and insects, and preserve the wood.
Clean the wood surface with plain water. If you are preparing a large item like a picnic table or deck, you can spray it with the jet setting on your garden hose nozzle. Allow the surface of the wood to dry before continuing.
Apply an oxalic acid cleaner to your wood, particularly if there are rust or nail stains. Galvanized nails and other metals in the wood may react with the tannins in the cedar. Remove the resultant black stains with an oxalic acid cleaner, which acts as a bleaching agent. You can also sandblast or pressure wash these types of stains as well as mold and mildew. If you have trouble removing mold and mildew, use hydrogen peroxide to brighten and clean the wood without damaging it.
Pour a few ounces of water directly on the wood to see if it has sealer on it. If the water beads up and does not penetrate the wood, it has a sealer that you need to remove before staining. If the water is absorbed, then the wood is sealer-free and can be stained as long as it is clean.
Strip any sealer off the wood with a chemical stripper made for this application. Use scrub pads, brushes or other manufacturer-recommended applicators to apply the stripper and remove the sealer. Be sure to wear protective clothing and eye wear when removing the sealer. Place dropcloths under your project area (unless you're working on a deck).
Sand the surface of the wood with 50- or 60-grit sandpaper to "scuff up" the wood and help the stain adhere better. Sand with the grain of the wood. Wipe down the wood with a damp cloth when finished to remove the sawdust.