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.
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 run into uneven or blotchy paint, the best thing to do is start over. The first crucial step in getting back on track is to prime the area you're painting. Once your primer is dry, begin painting—this time knowing that you've primed your surface and set your project up for success.
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.
Wall condition: If your walls are in good condition, you may only need one or two coats of paint to achieve a smooth, even finish. However, if your walls are rough or damaged, you may need to apply additional coats to cover up imperfections.
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.
If the humidity is too high, the solvents in the paint will take longer to evaporate. This long drying time cause the paint to dry with a darker appearance, though it can also lead to uneven drying, streaks, and paint discoloration.
Unfortunately, roller marks will probably not go away when the paint dries out. However, as the paint dries some of the roller marks will become slightly less noticeable. But simply waiting until the paint has dried won't solve the problem completely.
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.
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.
Prime or seal surfaces before applying the topcoat to ensure a uniform surface. Spot-prime any patched areas to level off the porosity of the surface. Apply an additional coat to even out sheen irregularities. Thin any touch-up coating to help it blend in better.
Glossy and satin sheens are more likely to show imperfections, but some matte sheens can be challenging to clean despite being better at hiding blemishes. Choosing a more middle-ground sheen, like eggshell, could be the best solution when your goal is to hide imperfections.
Reapply another coat to fill in bare spots. If there are clumps or bubbles on the painted surface, sand it, wipe clean, and reapply a coat of paint. To avoid streaks or lap marks from a roller, maintain a wet edge by applying paint toward the unpainted area and then back into the just painted area.
So you have two choices - either sand the whole wall smooth and repaint all of it or get a mini roller and put a few coats of paint on the patches with that which should build a bit of texture and might help. To be honest though, starting with it all flat would be the only way to lose those patches completely.
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.
Without sanding, the new coat of paint might peel or cause an orange peel texture. Once sanded, clean the entire surface and scrub away any leftover dust, debris, or grime. Keep in mind that nothing gets smoother by adding more paint, it only gets smoother by sanding between coats.
The best way to make sure each coat of paint dries evenly is to use the right tools and apply a thin, even layer of paint with each coat. Using a paint roller will help distribute paint evenly and apply a thinner layer than a brush, which often holds more paint than needed, leading to unwanted drips.
DIY beginners sometimes assume that one coat of wall paint will do – and end up with patchy or thin paintwork. Usually, you'll have to apply at least two coats of paint to achieve a smooth, even finish. Applying multiple coats also helps build up the paint so it's more durable, and less prone to chipping.
Before you start a paint job, you actually want to wet the paint roller cover with water. “This primes the roller cover to soak up as much paint as possible,” Barr explains. But don't go too crazy—Barr suggests removing excess moisture with a paper towel and a good shake of the roller so it's just slightly damp.
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.
You've painted in the wrong weather
If you attempt to paint in full sun or when it is very hot outside, the paint will dry too quickly and won't adhere properly. On the other hand, when you attempt to paint when it's too cold and wet, the opposite will happen and your paint will dry very slowly or not at all!
There are several ways to determine whether a surface is dry: OIL BASED products are dry if they are no longer tacky and do not emit a smell. WATER BASED products are dry if they no longer feel cool to the touch and a powder will form with light sanding.