|Get up to Speed on Steam
A report from the field describes a promising paint removal method.
For more than two centuries, we've harnessed steam for tasks as diverse as powering ships, heating buildings, and making electricity, so why didn't we think of it for stripping paint? After experimenting with different methods, we found that steam provides a relatively safe and convenient way to remove heavy paint buildup from old houses.
||After steaming for a few minutes, paint film about as thick as a dime stays soft for 10 to 15 seconds-plenty of time to scrape it off while protecting hands with thermal gloves.
Photo Courtesy of John Leeke
A Safer, More Efficient Alternative
Because the steam softens the paint film, you can scrape it away more easily for house restoration and historic preservation projects. Effective for removing paint from wood exteriors, interior walls, and window work, steam offers advantages over mechanical scraping and shaving, chemical stripping, and dry-heat methods in these areas:
Helps control lead health issues and eliminate the lead fume risk.
Reduces the risk of fire, compared to dry-heat methods, by keeping the paint surface below 212 degrees Fahrenheit.
Avoids fumes from chemicals and heat decomposition of binders in old paint that are common with chemical and dry-heat methods.
Uses a portable steamer that can be transported easily to work sites, even up on scaffolding.
Requires moderately priced equipment ($100 to $300), with lower operating and supply costs than chemical paint removal.
Lowers residue disposal costs compared to chemical paint removal.
I first learned about steam paint removal in the 1970s, when a preservation contractor experimented with steam to remove heavy paint from the side of a house in New Hampshire. According to the story, the steam removed paint all right, but the steam-generating equipment was, perhaps, too dangerous, so the contractor dropped the idea. Fast-forward to the 1990s, when there were reports of British workers steam-blasting graffiti off of stone in England and someone from Australia using a wallpaper steamer on paint. I just kept scraping away with my noisy hot-air gun and gooey chemicals.
Then in the late 1990s, my colleague Marc Bagala developed the steam chamber method of removing all of the paint and putty from a window sash by sliding it into a stainless-steel, steam-filled enclosure from an industrial-grade steam generator. I took the students in one of my window workshops to see this marvel, and it really works.
Later, one of my students, Dave Bowers, a window restoration specialist in New Hampshire, built a steam box powered by a portable steamer. Dave told me it worked great just holding the steam head on the sash. So, after encountering decades of examples of steam at work on paint, it finally dawned on me that the right steamer would work on any surface with heavy paint buildup. Now I use a steamer routinely and have trained a half-dozen crews around the country in its use.
Here was the setup on a recent project. To remove paint from a barn loft door, I set it on an easel in the workshop, and I plugged the steam generator into a 120v electrical outlet on a 15 amp or greater circuit. Next, I ran the black hose from the generator to the steam head, which I held flat against the paint film. We always follow lead safety work practices, so I was outfitted with a hat, respirator, and floor containment unit made of 6-mil plastic to catch and control lead paint debris. My gloves were particularly suited to working with steam: thick fabric for thermal protection and a waterproof coating in the palm and fingers. Other standard safety practices include wearing long sleeves, pants, and goggles, and powering the steam generator through a yellow Ground Fault Circuit Interrupter as a safeguard against electric shock.
After 30 seconds to a few minutes of steaming, the paint film was soft enough to remove with a stiff, slightly dull, putty knife. During removal, we shifted the steam head to the next section. The steamer left a slight paint film residue that when soft was easy to remove with a sharp pull-type paint scraper. The result was a smooth, clean surface ready to paint.
How It Works
Steaming makes paint removal easier in two ways. First, it softens the paint film by heating it throughout to between 190 and 200 degrees. As the water vapor condenses on the cooler surface of the paint film, latent heat in the water vapor penetrates the paint film by conduction. At first, the thin film of water forming on the paint surface helps conduct heat. As the film of water on the surface thickens, it impedes the transfer of heat. The paint warms up more quickly on vertical surfaces because the water dribbles away, allowing more vapor to condense closer to the paint surface.
Furthermore, steaming loosens the paint from the wood by introducing water between the paint film and the wood surface. This interaction occurs when there are breaks in the paint film, such as alligatoring, cracks, and areas of missing paint. Moisture migration occurs by simple capillary action, not by the pressure supplied by the steam generator. Sometimes, I notice the steam traveling between layers of paint because water percolates up out of the cracks in the paint film outside the steam head.
Spraying steam with the hose of a wallpaper steamer has little effect on the paint because the rig does not transfer enough heat to the paint film. The steam is too busy condensing within the air and loses its latent heat before reaching the paint surface, and the water vapor must reach the surface of the paint film to soften and loosen it. By using a steam head to exclude air as the steam approached the surface, we were able to transfer heat more effectively. Currently, we are making our own steam heads to match the size and shape of the house parts on which we work.
After testing several kinds of portable steamers, we are now using professional-grade steamers made for the clothing and fabric industry. Wallpaper steamers are a possibility when they operate at 1500 watts or more. They generate atmospheric pressure steam, not live steam or steam under pressure, which is entirely too dangerous and expensive for this use. The plastic, consumer-grade steamers that you see on the TV infomercials don't generate enough steam volume and may not hold up to the task. (However, from my perspective, there is no such thing as a bad product, and these consumer-grade steamers might be good for very limited, delicate, square-inch-by-square-inch paint removal.) The so-called high-temperature, household steamers that make a blast of steam only raise the paint temperature up to 165 degrees, which is not hot enough. Ordinary steam irons work on your shirts, but definitely not on paint. Although we continue to experiment with different methods, steam is another implement worth adding to your old-house tool kit.
For video clips and more information about the methods and equipment used to steam paint, visit www.HistoricHomeWorks.com.
The Portable Steam Paint Stripper
P.O. Box 542
Weare, NH 03281
The Steam Stripper
Window Restoration Systems
535 River Road
Brunswick, ME 04011