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Latex over Oil : A Hard Lesson Learned
Art Mulder / April 2006
I’ve been a homeowner for over 10 years, and have done a fair bit of painting over that time. So I thought that I pretty much had this room-painting gig figured out.
About five-seven years ago I painted a bedroom with a light blue oil paint. Ordinarily, I would not touch oil, however this was a 90% full can that had been left by the previous owner. So I thought that this was a good way to use up the paint. (That was a big mistake. The room was unlivable for 10 days after due to the odour. Never again. It was also a big mistake for another reason. Read on...)
Now came the time to paint again. This is a kids room, and we decided to paint some broad (14” wide) vertical stripes. So my wife washed down the walls with TSP. Then we painted two coats of CIL satin paint (medium blue) as a base colour. After a day we measured, marked, and put up green painter’s tape to mark off the stripes. Then we painted two coats of darker blue for the stripes.
Already we noticed a few problems. While measuring for the stripes, the tape measure left a scratch on the base colour that scraped right through both coats of paint. Hmm. I figured this was an anomaly. But after finishing the stripes, the size of the problem became clear.
Once the paint was fully dry we peeled back the tape. In two or three spots the paint just peeled back with the tape. We were shocked. Dozens of strips of paint, up to 3 inches long, came peeling back with the tape. And not just the top (dark blue) coat, but the base (medium blue) coat came up also. It peeled right back to the original paint.
The experienced (or professional) painters out there are no doubt shaking their heads at me.
I was certain that what I was doing was fine. Even now, several weeks later, after having done lots of reading, I still find that the general advice out there is conflicting. For example, I have read in a few places that acrylic latex paint, which was what I used, can be safely applied over oil. (Not!)
After checking around for advice, I came to accept that the latex paint had to come off the wall. There was no product out there that we could paint over it and have “soak through and hold”. Believe me, this took some time, a bit of “mourning” if you will. After all that work on cleaning, painting, as well as the work with setting up the stripes... the thought of having to strip it off was almost heartbreaking.
(On the plus side, I did actually find that I didn’t like the striped effect. The paint colour was too dark. That was our slightly silver lining to that huge cloud.)
I first tried washing the wall with Methyl Hydrate. Yes, it took off the paint, but the process very slow. The rag would almost immediately become saturated with paint. I could foresee myself needing a few garbage bags full of rags if I was to continue.
Next I tried power sanding. Nope. Dust everywhere, and sloowwwww.
What worked, in the end, was water and elbow grease. We washed the wall with water. Once wet, the latex seemed to loosen up a bit, and paint scrapers would take it off.
The dark stripes – the ones with four layers of latex – actually came off much easier than the ones with two layers. The kids had fun with those stripes. With a bit of care they could peal back a layer of paint almost the size of a sheet of paper. See the photos below for some shots of the gang at work, and of some of the paint being peeled.
I didn’t try to keep track, but it took a fair bit of time to scrape all four walls of this twelve-by-twelve bedroom. I collected the paint fragments in a grocery bag, and ended up with a lump of paint peelings certainly larger than a full gallon can of paint.
Once 98% of the paint was off the walls, we washed again, and then painted on two coats of original Kilz primer. This was on the advice of an experienced painter that I chatted with over email. The Kilz primer is an oil based product. I was warned that it had a very strong odour, and so I painted with a respirator. But interestingly, and to our great relief, the odour disappeared within just a few hours.
Two coats of light blue latex (satin) went on next, and we’re at last finished. There is also an “after” photo, below.
I never, ever, want to do that again. And so I “embarrass” myself a bit here in public, in hopes that others can learn from our misfortune.
