More help for old radiators

Old House Web gets a surprising number of questions about repairing and refinishing cast iron radiators. In recent weeks two readers have been in touch, one with a question and another with some advice.

First, the question: a mechanical engineer in the Washington, D.C., area wonders, "How can I acid clean (inside) and refurbish radiators? Any cleaning product?"

Refinishing a radiator invariably requires careful surface preparation, which in itself can be time consuming. If the old paint film contains lead, as pre-1978 paints usually do, the process also can be hazardous. This is enough for most homeowners to deal with. When a radiator is so encrusted, inside or out, that it requires an acid cleaner, it's probably time to call in a pro.

Hauling a radiator to a professional refinisher is not a chore most of us would relish. Radiators are heavy, and they may have to be taken apart to get them out of the house. Professional restoration is not cheap. But it would seem the best option to me if repairs are going to be extensive, and assuming the radiator is really worth the trouble.

But there's another point of view.

Rick Bylsma, a third-generation professional painter and re-finisher in Michigan, had this to say: "The old timer boiler guys (my age) say to leave them alone. When they are removed and sandblasted, acid etched, put in high heat ovens, etc., their weakest links get weaker and that equals leaks. Many times they are not leaking because the crud inside is sealing the pin holes, kind of like a car radiator."

Our Washington reader is in luck. He can make this decision with some good local advice by calling Bob Reed at The Stripping Workshop (411 New York Ave., NE, Washington, D.C.; 202-544-1470).

But if you're going to strip and repaint cast iron radiators yourself, Bylsma suggests staying away from oil paint. The problem with alkyd coatings, he says, is they get brittle in time, and a radiator is something that expands and contracts continuously during the heating season. A loss of flexibility in the paint and a substrate that's always moving around is not a great combination for durability.

Instead, Bylsma recommends direct to metal (DTM) coatings, which he describes as rust inhibiting acrylics that hold their sheen and color better than oils. A number of manufacturers make DTM coatings, including Sherwin Williams, Benjamin Moore and PPG Porter Paints.

Benjamin Moore, for example, says its Super Spec DTM acrylic is both a direct to metal primer and a tough finish coat that inhibits rust and has excellent gloss and color retention. It can be used on a variety of materials, including metal, plaster, wood and wallboard. And, the company says, the paint "resists loss of adhesion due to thermal shock caused by radical temperature changes."

There are many DIY-friendlier projects than refinishing a radiator. However you proceed, don't expect miracles overnight and be extra careful whenever you're working around lead paint (for more, check the EPA's site, www.epa.gov/lead).