We have not imaged thick anodized aluminum, but I’m sure we can. We've experimented with 'laserable' colored aluminum, but the results did not meet our goals. During anodizing, an electric current passes through an acid causing the surface of the aluminum to oxidize. The oxidized aluminum forms a strong coating as it replaces the original aluminum on the surface. The result is an extremely hard substance called anodized aluminum. It can be nearly as hard as diamond under the right anodizing process (hard anodizing). It’s very tough and used in many industries including aerospace.

One concern was the corrosion of non-anodized aluminum in a salt environment. Many of us have seen aluminum lawn chairs virtually disintegrate after a few years outside at the beach. When we remove the anodized layer to produce the image, that would expose the raw aluminum. The atmospheric assault on the photo would not be good. The piece could be coated to protect it from the environment, but that presents its own maintenance issues unless we used a synthetic diamond. That's never been tested with aluminum.

We were also concerned about Galvanic Corrosion. One gets Galvanic Corrosion by having dissimilar metals in contact in the presence of an electrolyte. This might be an issue if we put an aluminum plaque on a bronze foot marker. Anodizing is a standard means of eliminating the problem. Once aluminum is electrically isolated the problem is gone. So that worry was no longer an issue if the aluminum was anodized on the reverse side, the side contacting the incompatible metal.

The reason we decided not to pursue the anodized aluminum for our tributes were the dyes used in the anodizing process. They are organic based, and we were told by anodizing experts that over time they had a tendency to fade. That happens with all organic based materials. That was deal breaker right there. We were after extreme longevity, even outdoors.

Also aluminum itself just doesn’t have the marketing appeal of surgical stainless, titanium, or bronze. Unfortunately, aluminum is many times associated with lawn chairs and pots & pans. I personally have never seen an aluminum tribute on a memorial stone.

Another technique some companies use is a Photo Etching compatible metal, usually aluminum, embedded with a silver halide material. When exposed through a negative film to an exposure lamp the silver halides in the material turn black and create an image. The unexposed halides are then washed away. This is not true engraving where metal is removed from the surface. At left is a cropped scan of a "Photo Etched" aluminum plate. The resolution can be very good using this technique. Click on the image for an enlargement. Sign makers and distributors say it can be used outdoors, but I would question the longevity since an emulsion is used in the process. If the aluminum has a color, its been anodized. I mentioned the fading potential earlier.

Plaques&Letters, who designs with and distributes Matthews Bronze, had this to say about Matthew's Metalphoto™ Portraits on their Web site. "Metalphoto uses a photosensitive aluminum sheet, available in either satin aluminum or gold-tone aluminum. The sheet is exposed using a film negative made from a photograph using a UV light source. The image is produced in a permanent black image on the plate. ...Metalphoto is recommended when the only art available is extremely detailed or the image itself does not have a lot of contrast (old photos, for example)."

This technique does not work on stainless. We, Immortal Memories™, can handle old photos and extremely detailed images on stainless, titanium, and bronze. If you would like to review a lot of good information, photographs, and products by Matthews, Gemini, and Trigard we invite you visit the Plaques&Letters Web site.