Mass paint removal

April 20, 2009 1:56 PM

How could paint be removed from a large, frequently painted object?

My friend's school in the U.S. has a "painting" campus tradition. They have a landmark object outdoors on campus (a rock or statue for example) and various student groups paint the object to advertise an event or just for fun. Groups constantly paint over the old paint, and the object has layers and layers of dried up and in some places peeling paint on it.
The other day we were talking about hypothetical pranks and how we might (hypothetically!) remove all the ancient layers of paint from this object (in this case, a statue made of some kind of metal) and get to see the real thing underneath (which probably nobody has seen in years and years and years due to all the painting). We couldn't really come up with any clever ideas aside from large amounts of chemicals. Any ideas on how many many thick, old layers of paint could be removed from an object?

posted by sarahj to Media & Arts (20 answers total)

A pressure washer might work but could damage the underlying statue, depending on what it is made of.
posted by indyz at 2:01 PM on April 20, 2009

You have basically two options: Heat and chemicals. Methylene chloride will remove that kind of paint -- I used it to strip seven layers of housepaint plus two layers of automotive from my first car, a VW bug.

Heat will work, it will cause the paint to bubble off. Usually. But then the paint will offgas nasty fumes.

The only other option would be some kind of super high-pressure water... but it seems unlikely to work.
posted by fake at 2:02 PM on April 20, 2009

A hammer, a chisel, and patience, if the object is anything like the repeatedly-painted object from my school.
posted by inigo2 at 2:04 PM on April 20, 2009

A heat gun (made for paint stripping, not a hair-dryer) and various scrapers, putty-knives, and wire brushes would get most of it off, but it would be a ton of work and you probably would want to wear a respirator that's rated for paint and VOCs.
posted by gyusan at 2:11 PM on April 20, 2009

If the object won't burn, definitely heat. Although metal might conduct heat away fast enough to prevent the paint from getting hot, but I doubt it. A heat gun will work but will be pretty slow. If someone feels like buying/making an infrared paint stripper, google that up. Those things can remove paint extremely quickly.
posted by GuyZero at 2:14 PM on April 20, 2009

Also, you'll need to pick up the scraped-off paint. It's more goop than you expect. Chemical strippers usually make the goop more toxic/will cause chemical burns, heat-striped paint will stink somewhat.
posted by GuyZero at 2:15 PM on April 20, 2009

Ready Strip works like Peel-Away but without the fume and environmental damage.
posted by nicwolff at 2:16 PM on April 20, 2009

I'll copy an old comment of mine:

There are at least nine different ways to strip paint. Each branch of the military uses from three to five "approved" methods, the last time I checked. Experimentation is the key.

I had about twenty-five years of various kinds of outdoor paint welded to a concrete faux-cobblestone surface. I tried scraping, heat guns, solvents, spinning steel wool, and giant rotating things that slammed the paint off and sent sparks shooting about five feet. Nothing that wasn't going to take a hundred hours or more to pull off of this porch and walkway.

Eventually, I used a mixture of turpentine and a caustic gel paint remover, covered over the whole surface, then used plastic sheets to keep it damp overnight. After that, it was just three hours with a powerwasher. The concrete was so spotless you could see the pores.

There's just no one size fits all paint removal method.
posted by adipocere at 2:17 PM on April 20, 2009 [2 favorites]

My high school graduation (1998) was held right across the street from Michigan State University's painted rock (it has its own wikipedia page if you are unfamiliar). Before the ceremony we were hanging out there; the outdoor facilities staff at MSU had dumped something on the rock to clean it off and the paint had become pliable and stretchy, like giant sheets of goopy dough. You could peel off layers easily, and as we watched, that's exactly what the staff did.

I give you this anecdote for two reasons: one, you might want to contact MSU's facilities department to see what they do to clean their rock, and two, the facilities department in charge of your (rock or item) might already be cleaning it off at semi-regular intervals, so there might not be as much paint as you'd expect.
posted by holyrood at 2:20 PM on April 20, 2009

Depending on how concerned you are with where the removed paint ends up, why not sandblasting or dry ice blasting?
posted by BitterOldPunk at 2:21 PM on April 20, 2009

If you could get the statue to it, a dip tank would be best. It's a big tank of extremely evil chemicals, unavailable to the consumer market, that the object is dipped in and left for some period of time. It's a bulldozer where anything you could do is a shovel.

But I hope it remains hypothetical. The many layers of paint are of inestimable value as the physical record of this tradition, and I suspect their removal would be mourned.
posted by dirtdirt at 2:26 PM on April 20, 2009

I'd use some kind of media blasting depending on the substrate. Walnut shells and plastic beads are fairly gentle. Of concern would be how old the paint is, older layers might be leaded and you'd want to capture the dust if that's the case.
posted by Mitheral at 2:41 PM on April 20, 2009

We had a fence at CMU which was also painted in the way you describe. After 80 years or so it collapsed under the weight of all the paint and they had to replace it with a concrete one (still regularly painted).

As far as your question goes, a heat gun should do it as people have said above.
posted by reptile at 3:37 PM on April 20, 2009

I remember reading that when the White House was first stripped of all its previous paint jobs, in the early 80s, there were 42 layers of paint taken off. I think I first learned this in a Trivial Pursuit question, but it is confirmed here. So getting off multiple layers shouldn't be a problem (and might make the job easier, since the paint will stick to itself more than the object).

But the fact that it's a metal statue that's been painted makes it more complicated - stripping metal is usually a bit more difficult than wood or plaster, and you might not want to scrape at a statue...
posted by mdn at 3:54 PM on April 20, 2009

In the chemical department, PeelAway is a relatively non-toxic remover. It's used in restoration all the time. I've used it many times.
Instead of removing all that history, why don't you do something interesting. Do some selective removal and create a new image that way.
Removing paint isn't a prank. It's a job.
posted by Carmody'sPrize at 4:19 PM on April 20, 2009

To remove all kinds of old paint, I swear by 5F5. Good thing this object is outdoors, because the mixture of toluene, methylene chloride, methanol, and 2-butoxy ethanol will work wonders on your brain. You might still favor a breezy night. Put a thick plastic drop cloth around the base, don neoprene gloves and safety glasses then slowly drizzle about half the 5F5 down from the top. Old paint should melt away in a few minutes. Wipe down the statue with rags. You might also want to give it a sponge bath. You can clean up the detritus by rolling up your plastic tarp and taking it to the dump.

Here's why you shouldn't do this using any method - if this object has been painted for the past 35-40 years, chances are there's lead, cadmium, and other heavy metals in the mix. No matter how you strip the paint, you'll be putting this stuff into the environment in the surrounding area, into your lungs, and if you don't dispose of it properly, into a landfill where it doesn't belong.

I mention the above method for someone who has to do this on a much smaller scale and will make sure they know what to do with the waste afterward. I agree that if you do this, consider doing a partial section so it's far easier to contain. And if you have a statue with a free appendage, I recommend that you buy an empty paint can, fill it with stripper, and affix it to the statue to steep for a while. Put all the detritus into the can, seal it up and take it to the dump.
posted by plinth at 5:01 PM on April 20, 2009

We used to use a jackhammer to chisel paint off an old cement floor that was covered with many, many thick layers ( 4-5 inches) of dried paint. Ear protection ( plug and muffs) and goggles were a must have as it was in an old cement room. It wasn't a very pleasant job. very time consuming. If theres as many layers as it sounds in your situation, you'd probably have to chisel it off somehow too, but most likely will harm the statue to some extent at least in the process. Seconding dirtdirt about removing it and dipping the statue in a tank. But there would be no way of knowing how many layers there were ( as well as knowing where the thickest parts were) and when it might be "done".
posted by Taurid at 5:51 PM on April 20, 2009

Here is an example of a similar project (it can't quite be called a prank). Rather than strip the oft-painted object, students gave it a trompe l'oeil makeover.

The faux brick design was Brown’s idea, although she originally planned to imitate old stone. “We decided to mimic the brick right next to the bridge [on the wall surrounding Westminster Presbyterian church] to make the painting more convincing,” she says.

posted by Orinda at 6:16 PM on April 20, 2009

On the disposal of paint-stripping supplies: first see if your area has a household hazardous waste dropoff station.

My experience with an infrared paint remover (which is supposed to get hot enough to melt the paint but not hot enough to aerosolize any lead that's in it) on wood trim is that it did a great job on the more recent paint layers but really didn't work on the older layers, which would have been about 80 years old - not sure if they were lead or milk paint or what but they were tough. Also, the thing cost hundreds of dollars.
posted by lakeroon at 7:30 PM on April 20, 2009

Why not just do a faux rock finish over the rock? (I think you're talking about a rock ;)) That would probably be easier than all of the jackhammering and heating and chemicals, and would also probably have the intended effect.
posted by No New Diamonds Please at 11:22 PM on April 20, 2009