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To go from a dark surface to a lighter stain, you’ll need to apply a chemical wood stripper first. You can buy stripper at any home improvement store. Brush a thick coat of stripper onto the surface, then let it sit for 30 minutes to dissolve the finish. Use a plastic scraper or stiff-bristled brush to scrape off the dissolved finish.  Work in a well-ventilated room. Wear goggles and protective gloves when using stripper. Scrub the surface thoroughly with a mild detergent solution and steel wool before proceeding.  Refer to your stripper product’s instructions for additional details. Use a mild soap solution and microfiber cloth to wipe down a raw wood surface. If you’re applying gel stain over an existing finish, mix equal parts water and denatured alcohol to create a cleaning solution. Dip a microfiber cloth into it and wipe the surface down. Wipe off excess liquid with a paper towel.  Create a mild soap solution by combining 1 cup (240 ml) water with 1 teaspoon of mild dish detergent.  Let the surface air-dry completely before proceeding. Start off using a medium grit sandpaper, such as 120-grit. Sand the surface thoroughly, taking care to get into the nooks and crannies of the piece. Start on 1 side and work your way systematically to the other side to ensure an even and thorough job. After using medium grit sandpaper, sand the surface again using a fine grit, like 320-grit or 400-grit. The fine grit sandpaper gets rid of any remaining imperfections in the wood and gives you a perfectly smooth surface for applying the gel stain. If you’re working with a raw wood finish, follow up with 150-grit sandpaper. Using anything finer than that may prevent the surface from holding the stain well. Any dirt or sanding dust left on the surface of the wood will prevent you from getting an even stain and be visible once the stain dries. Use a dampened tack cloth or microfiber cloth to wipe down the entire surface. Be sure to get into the nooks and crannies. Gel stain can permanently stain both glass and metal, so mask off these areas before you apply it. For glass, cut thick paper down to size and use painter’s tape to attach it to the glass. Cover up hardware like knobs and hinges with painter’s tape.
Strip the surface if you’re going from a dark color to a lighter stain. Clean the surface thoroughly. Sand the surface using 120-grit sandpaper. Follow up by using a 320-grit sandpaper. Wipe down the surface to remove lingering dust and debris. Protect glass and hardware with paper and blue painter’s tape.