Aluminum Leaf

An Architectural Use of This Once-Precious Metal

As architectural conservators, we discover materials in locations we least expect. For example, aluminum is one such material that can be discovered in some of the most surprising places. Aluminum is found in nature mostly as alum, a compound of potassium aluminum sulfate. It was only in 1825 that a Danish chemist managed to extract aluminum from alum. Aluminum became a precious metal, which is one of the reasons that it was used as a pyramid cap on the Washington Monument in 1888. Weighing in at 6 pounds, it was the largest aluminum casting produced at that time and the first architectural use of aluminum. With increased production at the beginning of the twentieth century, the price of aluminum dropped dramatically. While no longer a precious metal, it continues to be a useful one.

One of our unusual finds was the use of aluminum leaf in a private house.

Leaf, sometimes called “foil”, is made of malleable metals, such as aluminum, copper, tin, and gold, and hammered or rolled into very thin sheets of metal. During a finishes investigation of the house, we discovered that one room had both the walls and ceiling covered in aluminum leaf. Further research determined the room was originally the hallway and was not only leafed, but stenciled, hand painted, and glazed during an alteration between 1872-1876. It would have been a spectacular space.

A word of caution to anyone who finds silver-colored leaf: do not assume that it is aluminum. Have it tested. Silver-colored leaf in at least one Newport mansion was found to be platinum.

Figure 1: 1870s aluminum-leafed wall with glaze, stencil, and hand painting (private residence).