The Walls Were Not Prepped or Primed Properly Sometimes, paint streaks aren't caused by poor technique, inconsistent coverage, or too much paint. If your walls aren't prepped properly, then the paint might have trouble adhering to the wall's surface. This can lead to clumps, drips, and paint streaks.
Reapply Paint: With a clean brush or roller, apply paint over the sanded area. If you're using a brush, follow the original stroke direction to ensure consistency. It might take more than one coat to completely cover the streaks, so let each coat of paint dry thoroughly before applying the next.
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.
If you've noticed those pesky streaks on your painted bathroom walls and wondered what they are, the technical term for them is "surfactant leaching." The streaks tend to appear in high-moisture environments such as bathrooms and are the result of water-soluble ingredients in the paint migrating to the surface.
Having paint streak is very common when not applying enough material, or using tools that don't hold enough material to disperse it properly. You want to make sure the roller has a uniform amount of paint on it while rolling, if it starts ``screaming'' at you on the wall, there's not enough paint left on the roller.
Will streaks go away when paint dries? If you see streaks in your paint while it's still wet, there is a high probability that they're going to be there when it dries. So, unfortunately, you're going to have more work ahead of you to get rid of them.
Applying paint in even, uniform strokes is essential for a streak-free finish. Start from the top and work your way down, maintaining a 'wet edge'—this means each stroke slightly overlaps the previous one before the paint dries. This technique helps to avoid marks and ensures a seamless blend between strokes.
When newly applied latex paint is exposed to high moisture or humidity while it's drying and/or curing, the surfactants can rise prematurely to the film's surface, producing a residue or splotches. This residue can be sticky, discolored, glossy or soapy in appearance.
Also, a second coat of paint helps remove roller marks by allowing you to feather out some of the unevenness in the finish. You can do this by overlapping the uneven areas to create a more uniform finish. However, you need to apply the paints with the proper technique for this to work.
First, gently dab a stain with a damp rag or non-abrasive sponge, as it may come off without the need of soap or a cleaner. If that doesn't work, dip a damp cloth in dry baking soda or a solution of baking soda and water, then gently scrub the mark. Use a stronger chemical cleaner if needed, but only after testing.
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.
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.
The more reflective a paint finish is, the more it will show streaks and imperfections. Flat or semi-gloss paints are best for walls with texture. The paint can streak if it is the wrong type; for example, if you used an oil-based prime coat, but a water-based paint on top, you'll have issues with adhesion.
What Causes Brush and Roller Marks? Application of additional paint, or re-brushing or re-rolling, in areas where the paint has partially dried. "Working" paint too much during application (e.g., applying too quickly or for too long). Use of the wrong type or nap size of roller cover.
Patchy paint can result if paint has been applied unevenly. Patchy paint can be down to a variation in surface absorption. Walls might appear patchy if they have variation in texture. Using paint that is not fully mixed can cause a patchy appearance.
First, roller marks are a common culprit. These can occur when the paint roller isn't fully immersed in the paint or is applied unevenly, leaving a patchy, streaky appearance once the paint has dried. Second, brush marks are another common cause of streaks.
Solution. Use the proper roller cover (avoid too long a nap for the paint and the substrate) and ensure adequate film thickness and uniformity. High quality paints also tend to roll on more evenly due to their higher solids content and levelling properties.
Why it happens: Uneven or blotchy paint occurs when you've either skipped priming or not adequately primed your wall before painting. This can also result from not applying enough coats of paint to get a uniform finish.
Streaking can occur if your roller was not sufficiently cleaned and left loaded overnight with paint. Next time you use it, the paint will still be on the roller and cause streaking. Improper loading of paint on the roller can also cause streak marks.
You want to use even, consistent pressure when painting. Remember, pressing too hard will leave behind roller-edge streaks. Not pressing hard enough will lead to inconsistent paint coverage. Practice on a loose piece of drywall to get the feel down before painting your wall.
Maintain a Wet Edge: To avoid paint streaks and overlap marks, always maintain a wet edge by painting over a section before it dries completely.
Using too much water, the wrong cleaning products, or not drying the walls properly afterwards can all lead to streaking. Even if you don't see the streaks right away, they might show up later as dust sticks to any cleaning residue left on the wall.
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.