To weather wooden shingles and siding artificially, it is necessary to coat the wood with a substance that reacts with the wood to change its color. Baking soda mixed with water or a combination of metal scraps mixed with vinegar artificially weathers wood.
When weathering wood, begin on a warm, dry day to ensure that the wood dries within one day. Determine which method to use by comparing the existing siding with the options available for aging wood. Baking soda produces gray wood, vinegar and metal produces a darker stain, and using a wire brush on the wood gives the material a rugged appearance.
Mix baking soda with water by adding 4 ounces of baking soda per gallon of warm water before applying to the wood. To weather siding, use a garden hose sprayer attachment, and saturate the wood. Allow the wood to dry naturally to achieve a weathered, gray look. The Lumber Baron suggests rinsing the baking soda solution off after the lumber has reached the desired color.
Lowe's recommends allowing two steel wool pads to soak in 2 cups of white vinegar for 12 to 24 hours to produce a solution that artificially ages wood. This solution is typically used for darker woods. Strain the solution. Then apply it in a thin layer, and allow it to dry. Sand the wood smooth, and apply a coat of polyurethane finish, if desired. Wood may also be stained to the desired color using gray or black stain to match existing siding and shingles.