Just for anyone here concerned.

Aviation radiators (inline engines of course and in many cases fuel cells) were not painted or covered in pigmented dope. Brass components were soldered together in the normal manner and then the whole unit was double dipped in a liquid solder.

Just bringing this up for anyone doing these items.

You are right, Stephen, a layer of paint would impede heat transfer quite drastically - but what about the protective grill ? Did the red around Rickenbacker's Spad nose extend onto the protective mesh, for instance?

Clive

Actually the shutters were infront of the radiator & its components. In one ihe head-on image of Rickenbacker's Spad show that these were not painted. In a later image the shutters are dark like the engine shroud. The whole Spad XIII radiator was double dipped in solder.

Here is a shot of the Spad XIII radiator on its side.