What Causes Rough and Grainy Paint Finish?

[SanOlive]

That's due to poor craftsmanship. The wood surface should be repeatedly sanded with wood sandpaper to remove burrs and achieve smoothness. Residual glue at wall joints and other bonded areas should be scraped off with a putty knife or finely sanded. If there are color spots or uneven color distribution on the surface, the wood should undergo a pre-bleaching treatment to ensure uniform coloration. Detailed explanations are as follows: 1. Repeated Coating: Metal components must have dust, oil stains, welding slag, and rust thoroughly removed from their surfaces before applying rust-proof paint. Unless otherwise specified in blueprints, apply at least two coats. 2. Paint Selection: Choosing a pneumatic paint mixer requires considering multiple factors including power type, applicable materials, layout form, processing capacity range per batch, mixer type, material category, application fields, mixing method, and pneumatic power. Applicable materials include liquids, paints, chemicals, food products, adhesives, inks, etc. Application fields cover chemicals, construction engineering, food, pharmaceuticals, paper industry, etc. Layout forms include horizontal, vertical, cycloidal, and coaxial configurations.

[Selena]

I just helped a friend deal with a similar issue. If the paint surface feels gritty, it's most likely due to problems during the spraying process. A dirty working environment can easily lead to dust and small particles sticking to the paint, especially when working outdoors where wind can blow all sorts of debris onto the surface. Incorrect paint mixing is another common issue—if it's too thin or too thick, it affects the flow, resulting in a bumpy finish like a pockmarked face. Poor spray gun technique can also cause trouble; holding it too far away or moving too quickly can cause the paint mist to dry before it has a chance to blend properly. Rushing to spray without proper sanding is another hidden danger, as surface dust can get trapped in the new paint layer. High humidity can also introduce moisture, leading to bumps. The best approach is to work in an enclosed paint booth, where the technician can take the time to sand thoroughly, control temperature and humidity, adjust the spray gun distance and movement speed, and apply thin, even coats without rushing.

[VonOwen]

Yesterday my neighbor asked me why there were so many bumps after DIY touch-up painting. I immediately spotted the issues. Poor surface preparation was the key problem - the old paint layer wasn't thoroughly sanded smooth, and stains/rust spots weren't completely removed. Incorrect paint mixing ratio is even more common: too much thinner makes the paint overly fluid causing splattering, while too little dries too fast forming particles. Spray technique matters greatly - holding the gun too close causes paint buildup and bubbles, while too far results in poor atomization and direct particle formation. Incorrect air pressure is frustrating too: too high blows away paint mist, too low causes uneven application. If the spray booth's air filtration fails, airborne contaminants stick to the wet paint. Finally, problematic drying conditions (like humidity causing moisture bubbles) create texture. Always wear PPE, test equipment beforehand, and ensure a dust-free environment before starting.

[McBarrett]

This situation is quite common in auto repair shops, usually caused by three factors. A poor spraying environment is the most critical—dust, small insects, or even lint sticking to wet paint immediately form particles. Sloppy craftsmanship is also problematic; insufficient stirring time causing pigment sedimentation or incorrect dilution ratios both affect film-forming quality. Equipment factors are easily overlooked—clogged spray gun nozzles can produce lumps, and air compressors not drained accumulate moisture that mixes into the paint. Substrate preparation issues are also major concerns, such as residual dust and debris not being blown off after sanding, or rushing to apply topcoat before the primer fully dries. The solution is actually simple: maintain a clean environment, mix paint strictly according to proportions, perform regular equipment maintenance and cleaning, and thoroughly clean surfaces with degreasing cloth before spraying.