One of the most common problems you'll encounter with antique chairs you find at flea markets, estate sales or garage sales is missing seats. That's also why these chairs can be purchased at bargain prices. Many people shy away from buying these lovely old "birds with a broken wing" because they don't know how easy it is to restore them. The secret most people don't know about missing chair seats is that reproduction antique embossed leather chair seats are readily available by mail order on the Internet with fabulous Victorian designs of flowers, geometric patterns, and artwork of birds. They are made from a surprising composite of materials--compressed paper and plastic fibers and polymer--and replacing them is within a do-it-yourselfer's capabilities.
Measure the diameter (or square) of the chair seat opening and add an additional 2 inches to the measurement to allow for tacking and gluing.
Draw out the dimensions for the chair seat on the back of the new composition seat. If it is circular, find the center point first. Then use the large compass to draw in the edge of the round seat.
Cut the composition seat with the band saw or hand scroll saw, using a fine tooth blade. Sand the edges of the composition seat with the fine sandpaper when finished.
Stain the composition seat to match the wood tone of chair. If the chair is part of a set of antique chairs, stain to match. For single chairs, usually a lighter tone of stain is more attractive. Allow the seat to dry overnight before applying varnish.
Varnish the composition seat with the clear acrylic varnish to protect the surface. Follow recommendations on the label for multiple coats. Consult with your paint and varnish supplier to make sure the varnish is compatible with the stain.
Prepare the area around the opening of the antique chair for adding the new seat. Remove any tacks, brads or staples. Scrape away any residue or glue from the previous seat.
Sand around the chair seat opening so the area is level, clean and ready for the installation of the composition seat.
Apply a bead of carpenter's wood glue to the bottom outside edge of the composition seat about 1 inch in all around. Smooth the bead of glue with your finger and let it set up slightly until it is tacky. Apply another bead of glue to the chair around the opening, also about 1 inch in. Smooth out that bead of glue as well and allow it to dry slightly until tacky.
Position the seat over the opening and press down firmly. Hammer four tacks into the seat to secure it in place--one at top center, one at bottom center, one at center left and one at center right. After these four tacks are in place, complete the installation by hammering tacks all around, equidistant from each other until finished.