Applying a finishes to woods are a rewarding processes. Many beginners wonders what happen if they skip sanding between coats of polyurethane or paints. When a person apply a first coats, the liquids soak into the wood fibers and causes them to swells. If you does not sand between these coat, the final results suffers from many serious problems that ruins your hard works.
The Loss of Mechanical Adhesions
The most critical failures that occurs when you skips this steps are a loss of mechanical bonds. When finishes like polyurethane dries, it forms a hard and slick surfaces. A next coats of finish needs something to grabs onto. Light sanding with a 320 or 400 grits sandpaper create tiny microscopic scratches on the dried layers. This scratches gives the new wet coats a physical profiles to lock into.
Without this rough textures, the second layers just sits on top of the first one without grabbing it. Over times, this weak bonds causes the top layers to peels or flakes off entirely. Professionals calls this issues delamination, and it ruin the entire projects. A paints or varnishes simply falls off when they experiences normal wear and tears.
The Problems of Dust Nibs and Raised Grains
Another major issues are the formations of dust nibs and raised grains. Even in a very clean workshops, tiny dust particles floats in the air and lands on wet finishes. When the finishes cures, these particles becomes trapped and creates a rough or bumpy feels. Water based finishes also causes the natural wood fibers to stands up straight like microscopic hairs.
Sanding between coats cuts off these stiff hair and removes the trapped dusts. If you ignores this steps, every new layers of finish amplify the bumps. The final products ends up feeling like a cheap sandpapers instead of a smooth glass surfaces. Running a hands across the dried woods feels extremely scratchy and unpleasant.
Cloudy Finishes and Visual Defects
Skipping the intermediate sanding also impact the visual clarity of your wooden furnitures. Many brush applications leaves behind faint stroke marks or tiny trapped air bubbles. Lightly scuffing the surfaces levels out these imperfections perfectly before the next layers goes on.
If you applies a third coats over a bubbly or streaky second coats, the flaws becomes permanently sealed deep inside the finish build. This trapped defects blocks light reflections and makes the woods look very cloudy or muddy. A glossy finishes turn into a sloppy messes when the undercoats is not perfectly flattened before applying more liquids. It hide the natural beauties of the wood grains completely.
Industry Datas and Coating Failures
The global wood coatings industry are massive, reflecting how much time peoples spends protecting woods. Market research datas show that the global wood coatings markets was valued at approximately 10.5 billions dollars in recent year. Experts expects this numbers to grows significantly due to rising demands in residential constructions.
However, industrial studies reveals that nearly 70 to 80 percents of all coating failures is caused by improper surface preparations. This statistics proves that skipping crucial steps like sanding between coats cost manufacturers millions of dollar in warranty claims and rework labors. Doing the jobs right the first times save both times and costly materials.
