Email #31 - Red or Orange in 1908?

Last Aug. 27 I sent you an email in which I speculated that the steel frame structure of Architecture Hall was orange in 1908, and not gray or black as seen in the historic black & white photographs from that time. (See email #24 "Once We Were Orange"). That speculation seemed pretty solid because almost all of the steel columns exposed in the current renovation have significant traces of orange paint.

Professor Jerry Finrow then challenged my speculation by pointing out that steel structures of that era were commonly coated with red lead paint. See email #24a "No, We Were Red." Therefore the steel structure must have been red in 1908 and then probably oxidized to the orange color that we see today, he said.

Which is it?

Two important clues came in right away. First, recent M.Arch graduate Zach Price sent me a picture of a wooden boat that he had recently painted with red lead paint. It was the same orange as seen on the steel columns of Architecture Hall. Then Professor David Strauss shared a conversation that he once had with an elderly gentleman who - as a young child in the 1920's - was so impressed with the steel frame of St. Mark's Cathedral under construction that he called it the "Orange Building" for the rest of his life, even though the orange steel had long since been covered up.

So I scraped a sample of orange paint from Architecture Hall and had it assessed by Lab/Cor, an analytical laboratory in Ballard. Their analysis showed that it was mostly lead tetroxide (Pb3O4) the primary ingredient of red lead paint. So Professor Finrow is right about this: it is red lead paint.

After two nights of Googling and more conversations with the chemists at Lab/Cor, the full answer seems to be this: pure red lead, or lead tetroxide, is indeed a very bright red. But the commercial grade red lead used in industrial paints and primers is orange because it contains a significant amount of the impurity lead monoxide, about 10 percent. The orange color does not change significantly over time.

Red Lead Paint's greatest showcase is the Golden Gate Bridge in San Francisco. Initially it was painted with two coats plus a clear topcoat. The bridge was orange when it opened in 1937, and it is the same orange today. Along the way it got repainted with non-lead paints but they were careful to match the color to the original red lead paint. Indeed the Golden Gate Bridge defined the color "International Orange." In RGB that's r=255, g=79, b=0.

So I reassert with even more confidence that the steel frame structure of Architecture Hall in 1908 was orange.

John Stamets
Sept. 22, 2006

See also #24, #24a and #71