How to: Bathroom walls need more than primer

Image of a paint bucket. Bigstockphoto.com photo

Image of a paint bucket. Bigstockphoto.com photo - Using primer alone in a bathroom isn’t a smart way to go.

Question: I have been in my house 10 years and have painted many rooms. The thrill is gone. I am tired of choosing colors and tired of partial cans of paint sitting in my basement. I have just stripped off the dark wallpaper from the upstairs bathroom. I want the final color to be white. I have “all-purpose primer with vapor barrier” that I’d like to use up. What if I put on four coats of primer and no topcoat?

Arnold

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Answer: Using primer alone in a bathroom isn’t a smart way to go. Primer is formulated to stick to and seal a surface so that it is evenly porous. It also covers up stains and masks the existing color, which is especially useful if you’re switching to white or pastel from a dark or bright color or a painted pattern, such as stripes. To maximize the performance of primer, manufacturers use ingredients that do these things. That means they don’t have as much room for the ingredients that give topcoat paint its advantages, such as the ability to wipe off spatters and fingerprints.

To reduce the number of cans of leftover paint in your basement, consider mixing several shades of leftovers when you have a paint job where you want a color other than white. Just be sure you have enough of the combo color to complete the job, because it won’t be easy to duplicate.

And one more tip: Even though you are weary of painting, do not scrimp on prep time. When wallpaper has been stripped, it’s essential to remove all the residue before you prime and paint.

I live in a house built in 1930. Many of the walls are plaster. Do I have to use special primer or paint?

Sheeps Head Island, Nova Scotia

Plaster from the 1930s was made with lime and was highly alkaline when new, though that eased over time through a chemical change caused by exposure to air. Painters were advised to wait 90 days before painting. Today, in rare instances where there is new lime-based plaster, a quicker option exists: Use a primer made for fresh concrete and masonry, such as Loxon Concrete and Masonry Primer. Regular water-based primer can go over that.

However, because your walls are very well aged, you don’t need to worry about alkalinity of the plaster. And besides, the plaster probably has paint on it, so the issue is what will stick to that, not what’s underneath. Most likely, the top paint is water-based.

If the walls are clean and existing paint is in good shape, you can probably just get right to painting, using standard water-based wall paint. However, If you need to patch holes, definitely spot-prime the patched areas before you paint. An all-purpose water-based primer should work well. Prime the entire surface if you are making a dramatic color change; are planning to use water-based paint and think the old paint might be oil (or don’t know what the top layer is); or are painting where there might be grease or soap spatters that you couldn’t scrub off, as in a bathroom or kitchen.

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