I am occasionally asked about the ‘black’ paint that was applied to the U-2, after it was decided that the polished natural metal finish, or the gray paint scheme, made the jet too visible to opposition fighter pilots trying to intercept. How black was it? My answer is a bit complicated.
In mid-1958, after some experimentation, the CIA chose a paint that was widely used on US Navy aircraft at that time. It was named Sea Blue, and the standard reference number for this shade was Article Number Association (ANA) 607 (below left). Today it is better known by a Federal Standard number: FS 25042 (below center). But Sea Blue was almost indistinguishable from black at a distance, and under certain light conditions. It could certainly not be distinguished from black in the monochrome photos that were standard at the time. To make this point, I have reproduced a color photo of a Sea Blue-painted aircraft from the early 1960s (below left), and converted that photo to monochrome (below right).
Meanwhile, the USAF aircraft remained unpainted until 1962, when a light gray gloss paint was adopted to guard against corrosion. This lasted until later 1964, when they were hurriedly painted black to help protect them from MiG interceptors over North Vietnam.
The next change came in later 1965, when a very matt black coating was chosen to cover all remaining U-2s – both CIA and USAF. This was known as “Black Velvet”, and it really did soak up the light (below). It also supposedly made a small contribution to reducing the radar return, thanks to microscopic particles of a ferrous material in the paint which (simply put) dissipated radar energy.
A later and more sophisticated version of this paint is named “Iron Ball”, and is found today on the B-2, F-117, U-2 and other warplanes that don’t want to be detected.