Okay, so what is the proper technique for doing this? I’ve seen people on TV use masking tape to delineate stripes while painting. Whenever I try to do this, the paint creeps/seeps under the edges of the tape resulting in a very fuzzy line.
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Make sure the wall is very clean before putting the tape down. Seal it if need be.
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The bumpier the wall surface, the more problems you’re going to have.
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After you apply the tape, use a paint scraper to press and smooth it down.
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Let the paint dry all the way. Seriously, wait a day or two before taking up the tape.
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Before taking up the tape, use an X-Acto or box cutter to cut through the latex pain along the edge of the tape.
Make sure you’re not using masking tape. Even blue painter’s tape is “out” now. Green Frog Tape is the thing to use.
I also don’t think that leaving the tape on too long is the right way to do it. In my experience, you want to remove it when it’s wet so that the paint doesn’t dry to the tape and then come off when you take the tape off. You want to take it off right away.
From the Frog Tape How-To:
“Remove the tape immediately after you are finished painting. This will help prevent paint from bridging over the tape and tearing when you remove it. When latex paint begins to dry, it becomes rubbery (like a rubber band) and has a tendency to pull.”
I’m an artist who does acrylic paintings, and occasionally I need to use masking tape on canvas . . . which is even more difficult than on a wall. After I lay the tape down I go over the edge with my thumbnail, to close off the edge as much as possible. Then I paint over the seam with a colorless paint medium (it dries clear). This is the important step, because this is what will sometimes seep under the paint. But it doesn’t matter, because it’s clear. If the canvas has a rougher texture I sometimes use two coats of the colorless medium. After it’s totally dry, I then use the actual paint, and wait for it to dry somewhat before removing.
On textured surfaces, I use a scrub brush to push the tape into the texture so the paint doesn’t wick into valleys in the texture. press the tape down, then scrub it hard. If you take the tape off when wet, make sure you pull straight back or slightly favor the side of the tape with the wet paint.
Important to note about painter’s tape, don’t put it on the wall until you’re about ready to paint it. If it stays on a wall for too long (ie. over a week or two) it becomes really hard to remove and will probably leave residue behind.
Back in the day we would use scotch tape and then partially overlap it with masking tape. Scotch tape has a crisper edge,
That looks like good stuff. Thanks for the recommendation.
That has been my experience too.
This is a great sounding method.
Do you have any of the trouble you can get into with latex letting it dry on the tape – the bridging over and pulling off paint you wanted to stay?
We’ve done my son’s room a couple of times with stripes. Once vertical and another horizontal. I’ve used the frog tape which is nice stuff but the blue painters tape from 3M seemed to work fine also. Just press along the edge of the tape with your thumb to make sure it sticks good. I go along with the tip to remove the tape as soon as possible.
Once the tape was removed and it was completely dry we also went along the line with a very fine tip paint brush to touch up small errors.
We do get a lot of comments from visitors “how do you make your lines so straight!”
See the thread Painting the Trim with Perfection? over in General Questions. A couple of mentions of “backfill with caulk” and comments. The caulk seals the tape/wall interface to stop the leaking under the tape condition.
I bet there were a lot of comments about “backfilling” with caulk. 
When I did my walls I used very little paint along the tape edge, almost a dry brush. That way the paint couldn’t seep under the tape.
I didn’t have any trouble peeling the tape off. The paint broke along the line cleanly for me.
I would guess this method might not work as well for strongly contrasting colors. Mine was a shade difference, so a dry brush got enough color on the wall.
My painter friend says to run a bead of caulk along the edge of the tape to seal it. He can do this perfectly and easily. I can not.
I have peeled off big globs of latex before when I let the paint dry before removing the tape. I’ve also had the tape stick to the surface when I left it too long.