Restoring vintage furniture is a hobby of mine. I especially love collecting chairs designed by architects. These MCM parchment fiberglass shell chairs by husband-and-wife team, Ray & Charles Eames refinished spectacularly after many cycles of sanding and coating with marine solvent. The original steel bases were replaced with wooden dowel bases. Instructions Below.
I typically find decently priced vintage furniture on Ebay or Etsy. It can take years to collect a matched set, so obsession is key! As an investment, I will note that refurbished original vintage shell chairs increase in value, so I am constantly selling a finished set and starting a new project in a new color!
In a small circular motion, sand the surface with the sponge. The result should be a uniformly dull appearance. Fiberglass is self-healing so the sanding should remove minor surface scratches. Rinse surface and allow to dry overnight. Apply a thin coat of Penetrol with a microfiber cloth and allow to dry. I recommend three coats.