Birchwood Casey (Liquid)Birchwood Casey Liquid Patinas All are packaged in a concentrated form dilute up to 50% with distilled water. All Birchwood patinas are considered traditional patinas that will age or darken metal. Most of these patinas are sold concentrated and should be diluted with distilled water (up to 50%) before use. Once diluted, one gallon of Birchwood Liquid Patina generally covers 200 sq. ft. Liquid solutions for Bronze, Brass, and Copper (concentrated): M