Painting a Radiator

Scott Gibson, Contributing Editor

We are now getting ready to repaint a radiator in our house. We have sanded all the paint that will come off and are now wondering what type of paint we should use. We've heard that dark colors produce more heat. Any information would be appreciated. Our plan is to paint the radiator in place.

If there's no compelling reason to move the radiator, you've got the right idea -- paint it right where it sits. Moving several hundred pounds of cast iron isn't much fun, risking scarred floors as well as a very sore back.

There are a variety of options for dressing up an old radiator. In addition to simply adding a new layer of color, bronzing and polychroming are techniques that produce a more decorative surface. It just depends on how much effort you're willing to devote to the project. But be warned: it can be "tedious and time consuming," in the words of the U.S. General Services Administration's pamphlet on the process.

With 13,000 employees and a half-century of experience in fixing up office space for the federal government, the GSA has probably painted a few radiators in its day.

Use a primer and oil paint

Any paint pro will be happy to tell you that painting is 90% prep work. Grime, dust, loose or scaling paint all has to come off in order for a new finish to stick. Chemical strippers, a wire brush and even a ball-peen hammer (not necessarily in that order) can help.

In "moderately corrosive" environments, or if the surface is somewhat degraded, the GSA suggests an oil-based primer with a lot of zinc, such as zinc chromate, or red iron oxide paint made with linseed oil. Otherwise, use an ordinary oil-based primer.

If you're brushing on the top coat, you can use any oil-based paint you like. It should do just fine with the heat generated by the radiator. If, however, you plan on using an aerosol paint, stick with a high-temperature paint. Auto parts stores and stove shops sell it.

Do not use latex paint. It can encourage rust.

Use a paint brush designed for oil paint. Radiator brushes have long handles and angled ends that make it easier to reach into awkward spots, but any brush for oil paints will do.

Does the color matter?

Not really, at least according to the Johnson Paint Co. in Boston, Massachusetts, which sells radiator brushes, paints and other refinishing supplies. Very dark colors contain a heavier proportion of tints, and these coatings may not last as long as a lighter color.

The GSA thinks differently, suggesting that for the maximum heat transfer you should use a flat, black paint, which radiates heat more effectively than a glossy surface. Despite this difference of opinion, there seems to be no ironclad rule of thumb about color and heat efficiency. Go with what you like.

There's no disagreement, however, that a metallic paint or a bronzed top coat reduces heat transmission. So if you're already fighting the cold, you're better off staying away from these finishes.

Bronzed and polychrome finishes are the most decorative

Bronzing is a way of highlighting the decorative filigree that make some old radiators so handsome, or it can be used to coat the entire surface if you like that look. Bronzing powder is mixed with a special bronzing liquid then applied with a brush. A quart of bronzing liquid should be enough to cover between 250 and 300 square feet. It should be applied with a soft-bristle brush.

Polychroming is a fancy way of saying two-tone. The idea is to paint the entire radiator one color (after sanding and priming) and allow the finish to dry. This is the base.

Then apply the second color. While the paint is still tacky, wipe it away from areas where you want the base color to show through, usually the ornamentation.

If you have a very steady hand and are generally fearless around paint, you can always paint the ornamental parts of the radiator by hand. If it were me, I'd skip the coffee until the job was done.

Have a question? Write to me at scottgibson@securespeed.us.

About the Author
An accomplished woodworker and carpenter, Scott Gibson is the former editor of Fine Woodworking magazine, and a former editor at Today's Homeowner and Fine Homebuilding magazines. He also is former managing editor of the Kennebec Journal, a daily newspaper in Maine.

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