Photosensitive anodized aluminum, also referred to as photo anodized aluminum or photo metal, utilizes the porous nature of unsealed anodized aluminum to create a sub-surface image, either through exposure and development of an anodic layer impregnated with silver compounds (Type 1), much like traditional black & white photography, or through the use of a photomask (Type 2) in which the image is created through a variety of means, including chemical etching, color addition or color subtraction. Technology Type 1 photosensitive anodized aluminum is anodized aluminum that has been impregnated with a silver compound which, when exposed to a light source, creates an activated latent image. Upon development and fixing a black, silver-based image is formed inside of the metal. Type 1 photosensitive anodized aluminum is then sealed in boiling water similarly to common anodized aluminum. Sealing hydrates the aluminum oxide surface, trapping the image beneath the anodized layer. The combined benefits of UV stability and the high image resolution of silver photography along with the abrasion and corrosion resistance of anodized aluminum are used to advantage in applications where permanent product identification is critical such as equipment nameplates, IUID barcode labels, outdoor signage, safety/warning plates, machine control panels and fine art. Type 2 photosensitive anodized aluminum is typically coated with a photo resist, which may be of either the positive or negative type. Exposure of the photo resist through a negative and its subsequent development creates areas on the plate that are either protected by the resist or exposed to the effects of the dye, bleach, or etchant that are used to create the contrasting mark. Type 2 photosensitive anodized aluminum must be sealed just like Type 1. Common use for Type 2 applications are those where color (other than black) is desired on the finished product. The dyes used to create colored Type 2 plates can vary significantly in their heat and color fastness, so are often limited to indoor or short-term outdoor usage. Note that colored dyes can also be incorporated into Type 1 photosensitive anodized aluminum. History Type 1 photosensitive anodized aluminum was developed in 1950 by Horizons Research Incorporated and is sold today by Horizons Imaging Systems Group under the Metalphoto® brand name. Industrial and military specification Photosensitive anodized aluminum was qualified to Federal Specification GG-P-455 in 1965, a document that outlines the performance of Type 1 and Type 2 photosensitive anodized aluminum. Since qualification to