Lighten the space by bringing more light into the room. Remove heavy draperies and window treatments; opt for lighter variations. Install a skylight strategically placed in the room to create more ambient lighting and chase the shadows away. Install track lighting above the wood-surfaced wall to highlight your art collection or framed light-colored artistic prints hung pleasingly. Or add up-lighting designed to wash the wall with light. Go for furnishings with light-colored upholstered fabrics and airy designs.
Any number of lighter-colored paints -- such as gray, pale green, off-white or tan -- can work to lighten the color of the dark, rough-hewn wood walls without affecting the wood's texture. Vacuum the walls thoroughly to remove trapped dust and debris, because the wood holds onto dirt. Add a sealing primer to the surface of the walls to keep the paint even and prevent bleed-through at knots and denser areas of the wood. Apply the chosen medium to lighten the wood with a paintbrush meant for use with oil-based products. Let it dry.
Give the walls a coat of translucent color to tone them down. Whitewashing and pickling involves diluting a chosen water-based paint or primer in a 1-to-1 ratio with water for whitewashing and a 1-to-3 ratio of paint to water for pickling. While traditional whitewashing is done with lime, a paint-based whitewash will produce similar results. After thoroughly cleaning the wood paneling, coat the surface of the rough-hewn wood with the whitewashed paint or pickle mixture. Apply the paint between the grooves in the paneling or where the boards join first, and then cover the rest of the area. Work in small 4-by-4-foot sections to ensure adequate coverage. Wipe off the mixture before it dries to remove excess paint or glaze. Let dry, and decorate the wall if desired.
For the gray, weathered look associated with seaside beach cottages, purchase stain products specifically made to give wood -- even rough-hewn wood -- the look it would get when naturally lightened by the sun. Apply sandpaper to extremely rough patches of the wood to smooth it out a bit, and then remove all dirt and debris. Apply the sun-bleaching product directly to the wood and let dry. When you use paint, glaze or sun-bleached stains, open up the windows for good ventilation.
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