All of my 13 radiators have been painted. All are, to varying degrees, experiencing paint chipping. (Brand: American radiator; installed: 1927.)
In their original as-installed state, the radiators were unpainted. Instead of paint, they had a beautiful dark chocolate-brown patina. The surface had a medium/fine sandpaper-like texture. I really like the original color and texture.
I recently had one sandblasted. What an improvement! What I am left with, after the sandblasting, is:
1. Color: gun-metal gray;
2. Texture: the original sandpaper-like texture.
My original post-sandblasting plan had been to spray paint the radiator (primer coat, followed by gloss white coat). However, as the radiator sat for several weeks, I noticed that it spontaneously started oxidizing to a rusty-brown (i.e., red-brown) color. On a test area, I accelerated the process by wiping it with a damp sponge. Result: enhanced oxidation; same red-brown color.
So, now I am left with the texture that I want, but, color-wise, I get a red-brown color, versus the chocolate-brown that I want. Also, I am concerned that the oxidized iron (i.e., rust) will rub off.
My questions are:
1. Does anyone know how the original chocolate-brown patina was achieved?
2. And, more importantly: does anyone know if/how I can reproduce this same patina “at home”? (Instead of spray painting.)
3. If I leave the radiator to oxidize naturally (or accelerate the process with moist sponge) will the resulting rusty patina rub off (e.g., on clothing)?
A thought: I wonder whether, as part of the manufacturing process, a wash (or some type of coating) was applied. Such wash/coating would presumably achieve two purposes: i. produce the chocolate-brown color; and, ii. seal the surface, and thereby prevent oxidation and “rust rub-off.”
One-pipe steam. NG fired. 2100 sq ft heated space.
Utica Boiler PEG150C (150,000 Btu/hr Input) connected to 491 sq ft of radiation. Operating press 0.5 psi.