Patchiness in a painted wall can happen due to several factors, such as applying too thin a coat of paint, uneven surface texture, or not allowing each coat to dry properly before applying the next. Make sure to use quality paint and apply multiple thin layers for better coverage. For more, check out my Quora Profile.
There is a caulk and painters tape trick that worked well for me. First you place the tape then apply caulk thinly on the side you are painting then brush the paint on. Left a nice straight line on my uneven ceiling where walls meet.
You need to paint the whole wall. Prime the patch. Let dry. Sand the primer. Paint the patch. Let dry. Sand the whole wall. Cut and roll just that wall and paint the whole wall. Best results.
To troubleshoot, try ensuring consistent drying times between coats and experimenting with different application tools to see if that makes a difference. If you've tried rectifying the issue with no success, it might be worth considering starting fresh with a higher-quality paint.
Try to maintain a wet edge. When using a roller keep the open side towards the area just painted. Try to complete one full surface at a time. Paint in an even grid pattern from top to bottom.
How to fix uneven or blotchy paint: No matter how many additional coats of paint you add, this problem likely requires going back to the drawing board. If you run into uneven or blotchy paint, the best thing to do is start over.
Without primer, the touched-up spot will stand out, and it'll look a right mess. The trick is to blend the new paint with the original surface. Priming will also prep your surface for paint and seal any stains - especially those that wouldn't come off.
Lightly sand the troublesome area with 150-grit sandpaper, then tack the walls. That's painter lingo for “Wipe it with a cloth to get rid of dust.” (Easier than the lingo makes it sound!) Then re-paint the area, maintaining a wet edge—meaning, don't let the paint dry until you finish the wall.
If your roller runs dry, you'll find yourself with uneven patches, leaving your walls looking inconsistent. Also resist the urge to rework wet paint and trust the process… it will look patchy whilst drying! Another common culprit in achieving a patchy effect is not maintaining a wet edge whist cutting in.
Load your brush or roller with just enough paint to cover the touch-up area. Start in the middle of the touch-up spot, and work your way out to the edges. Without reloading the applicator, feather the edges by making light strokes that extend slightly past the edge onto the surrounding wall.
If you do end up with drips or runs in your paint job, just let them dry completely and then sand them down until they're flush with the rest of the wall. Once they're sanded down, repaint over them and they'll be good as new! Even if you're careful, you may still end up with paint on your ceiling.
Not Fully Loading the Roller
The roller needs to be fully loaded with paint to the core, otherwise you'll get air bubbles on your wall, resulting in “paint acne.” To avoid this mistake, roll back and forth on the roller tray until all bubbles are gone and the roller feels heavy.
Painting over existing layers of paint is usually the easiest option. A paint that has high coverage and a thick texture, such as our Claypaint or Lifestyle emulsions, will even out any hairline cracks and slightly bumpy surfaces. Both products can go over a multitude of wall substrates.
Drips and runs are a clear sign of a bad painting job. These imperfections are typically caused by applying too much paint in one area, or by not being careful during the application process.
Wall Touch Up Problem #4, Patching Issues
You can minimize this by priming in the patched area with a primer so it comes closer to matching the rest of the wall. In some cases, priming with wall paint you plan to use can also work.
Brush marks are caused by strokes that leave the paint with a rough texture and visible brush strokes. The rough texture and visible brush strokes can be easily covered in a second coat of paint by using a slightly different technique than you used for your first coat.
Use the correct amount of paint
Check the paint coverage on the side of the can to ensure you're applying the right amount of paint. Spread it too thinly and it will look patchy; spread it thick and it can look lumpy or uneven.