Painting Radiators Q&A

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Dear NH,

I recently bought a condo that was remodeled before I purchased it. The radiators in the unit were painted white (same as the walls). When the boiler kicked in, and the radiators started spurting to life, my joy was squashed with the smell of burning paint. A few moments later my condo was filled with smoke and I was choking from the fumes. A few questions:
1. Could this have been caused by using latex paint on the radiators?
2. Will I have to let the chemicals that were burning to naturally "burn off" before I can enjoy being warm again?
3. Is there an easy was to strip the layers of paint off the radiators?

SB from Minneapolis, Minnesota


Since most hot water systems don't get hot enough to cause paint to outgas as viciously you've described, I have a feeling that you must either have steam heat or a very high temperature boiler! Anyway, the heat drives off residual solvents and/or moisture that would normally dissipate over a period of weeks and months through normal aging. The heat just speeds the process up... a lot!!

It is a fact of life that any painted surface will stink for a while when it is first heated, even fire resistant paints. Most people are blissfully unaware of this until they have an experience like yours. If you had known, you could have run your heating system while it was still comfortable enough to open all the windows and give your place a good airing.

After you run the heat for a while, the paint will "bake in" and the odor will dissipate... just get a fan running and keep the windows open until the air is clear. I wouldn't bother to strip the paint, since you will then have to bake off the odor of the stripper.

And let me tell you... chemical stripping of radiators is a messy, tedious job and not for the faint of heart!  The most efficient method is to sandblast them... again messy but far more time-efficient!

Dear NH,

My situation is pretty basic. I am remodeling a farm house that was originally built in 1885. The house is heated with a one pipe steam radiator system that was originally coal - converted to oil first and now to gas. I have 8 beautiful radiators that are being stripped of the some dozen coats of paint by sand blasting with oxidized aluminum. 2 of then are done now and the detail is incredible! And with the paint gone the heat efficiency is so much better.

My question comes down to this: Do I need to coat them with anything for protection of the cast iron? If so what do I use?  I am having a heck of a time finding this answer - I have heard everything from Jet engine paint - to cooking oil! Any advise will be greatly appreciated.

JR from Lansing, Michigan

Yes, you should coat them. The overall appearance is better, cleaning is easier, they will be protected from rust, and you can use the paint to control the heat they radiate.

If you use any type of oil, such a cooking oil, you may protect the iron from rust, but you will also make future painting very difficult if not impossible, attract dust to the residual tack from the oil, and in general make their appearance less attractive.

You may use polyurethane if you want a clear coat. The best finish by far is a sprayed paint for durability and consistent appearance. A high temperature paint can be used, but it is not absolutely necessary. The temperature of steam is within the working range of most spray paints. Don't use a latex spray... it will not provide a tough enough finish. A gloss oil is the best.

Choosing the color is critical to control the heat output. If you paint the radiators black, they will generate much more heat than if you paint them white, "natural" silver or gray. I learned this years ago during the 1970's oil crisis, when solar heating and cooling was the "in" thing. I don't remember the specific scientific reasons, but darker surfaces both absorb and radiate heat better than lighter surfaces.

I remember making a mistake with radiator color in my first home, which had a similar steam system to yours... a former coal furnace... except it burned fuel oil. There was one bathroom in the house... a very small one on the second floor that had you sitting inches from the radiator... enough said! Anyway, I thought it would be aesthetically pleasing (read "look cool") to paint the radiator black. Well, the BTU output from this tiny radiator was so intense that I ended up repainting it white to make the room useable. After that I selectively repainted radiators black or white based on my heating experience in each room. Since most of the radiators were under covers, the color change was not noticeable, but the temperature difference sure was!

BTW, if you install a reflective metal shield behind each radiator, either aluminum or sheet metal, you will also increase the amount of heat radiated back into the room. Again, aesthetics rule.

Dear NH,

I want to paint my steam radiator and I do not want it to peel. Is it necessary to first prime it and what type of paint do I use, both for priming and finishing, latex or oil?

I can appreciate the overload of questions that you receive. But if you don't answer my lame question then who or whom can I turn to in my time of need? Better hurry, winter is closing in and I'll have to wait till next spring to paint. And if I don't get an answer then this can go on and on indefinitely and it'll be on your head that this little old radiator (well, it's not that little) will never see a fresh coat of paint.

Aren't you glad you started this web site and have to deal with wackos like me? Just kidding. If you can't get to my question , fine. I'll just have to ask my wife; she knows everything.

SR from Glen Ridge, NJ


I received both your messages. I honestly wish I received lots of lame questions... it would be less painful to have to skip over many of them. Unfortunately, just about all the questions I receive ARE important! Given the limited time I have to answer them (not being an Internet "wonk" and still working for a living), I try to give emphasis to the ones that seem to have the most universal import... such as yours!

If the existing finish is sound, you don't have much of a job. First, clean all dust and dirt from the radiator. Then, use sandpaper to roughen the surface slightly to give the new paint a better grip. Wipe the radiator down with Wilbond deglosser (whether the radiator has been painted or not)... this will remove any oils and help the paint to adhere. If the radiator is raw metal, you should use a bare metal primer before painting. If the radiator is already painted, use an oil primer if you want... it can't hurt but if your other preparation is done properly it may not be necessary.

Apply a finish coat of a quality oil-based interior paint. I don't approve of using latex paint because it is less heat resistant and less durable than an oil-based paint.

High temperature paint is not necessary... these are meant for really high temperatures such as industrial or automotive engine applications, far above the 200 or so degrees that a residential steam radiator reaches.

You could also use canned spray paint. Depending on the brand, you may not even need a primer over bare metal. Of course, using spray paint inside a home requires quite a bit of masking to protect objects from the spray.

Earlier I said "if the finish is sound". If your radiator is covered in chipping or lifting paint, you must remove all loose paint or the new finish will fail. This can be accomplished by sanding, scraping or even the use of a chemical paint remover. If the radiator has old paint that might contain lead, the safest method of paint removal is chemical, since this does not release lead into the air to the extent that sanding would. There are lead testing kits available at any hardware or paint store. If the radiator can be disconnected and taken outside, even better... though I know this is impractical for most situations.

I am not an expert in lead abatement, so my advise is limited to common sense... 1) use an appropriate respirator or dust mask for personal protection and 2) keep the dust down or contained through masking and/or "tenting" the radiator to keep the spread of lead dust within a controlled area. Because local codes vary as to lead issues, it's up to you to find out the laws in your area. Some codes are quite strict and the penalties can be quite severe... especially if you have young children in your home!

Because of the stress on the paint from the constant heating and cooling, don't expect your paint job to last forever. However, your care to preparation detail will extend its life by years!